Content area
Objectives
To investigate associations of the ‘weekend warrior’ physical activity pattern with mild dementia.
Methods
Participants in the Mexico City Prospective Study were surveyed from 1998 to 2004 and re-surveyed from 2015 to 2019. Participants were asked about leisure time physical activity at baseline. Those who exercised up to once or twice per week were termed ‘weekend warriors’ and those who exercised more often were termed ‘regularly active’. A Mini Mental State Examination (MMSE) was used to assess mild dementia at re-survey. Cox models were adjusted for age, sex, education, income, blood pressure, smoking, body mass index, civil status, sleep, diet and alcohol at baseline. The attributable fraction was defined as the proportion of cases that would not exist if all adults were to exercise once or twice per week or more often.
Results
The analysis included 10 033 adults of mean (SD) age 51 (10) years followed for 16 (2) years. There were 2400 cases when mild dementia was defined as a score of ≤22 on the MMSE. Compared with the group that reported no sport or exercise, the hazard ratio was 0.75 (95% CI 0.61 to 0.91) in the weekend warrior group, 0.89 (95% CI 0.78 to 1.02) in the regularly active group and 0.84 (95% CI 0.75 to 0.95) in the combined group. The attributable fraction was 13% (95% CI 5% to 21%). Similar results were observed when mild dementia was defined as a score of ≤23 on the MMSE.
Conclusions
This longitudinal analysis suggests that the weekend warrior physical activity pattern is associated with a reduced risk of mild dementia.
Correspondence to Dr Gary O'Donovan; [email protected]
WHAT IS ALREADY KNOWN ON THIS TOPIC
Prospective cohort studies in Africa, East Asia and Pacific, Europe and North America suggest that leisure time physical activity is a major modifiable risk factor for cognitive decline and dementia. However, there are no such studies in Latin America.
WHAT THIS STUDY ADDS
The ‘weekend warrior’ physical activity pattern may be a more convenient option for busy people around the world. In this prospective cohort study, the risk of mild dementia was reduced by an average of 15% in the ‘weekend warriors’ who exercised once or twice per week and by 10% in the ‘regularly active’ who exercised more often when mild dementia was defined as a score of ≤22 on the Mini Mental State Examination.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
To the best of our knowledge, this is the first prospective cohort study to show that the weekend warrior physical activity pattern and the regularly active physical activity pattern are associated with similar reductions in the risk of mild dementia.
This study is important because it suggests that even busy people can gain cognitive health benefits from taking part in one or two sessions of sport and exercise per week.
Introduction
The number of people living with dementia is predicted to increase from around 57 million cases globally in 2019 to around 153 million cases in 2050.1 The proportion of people living with the condition is predicted to increase by around 75% in the UK and other countries in Western Europe and by around 200% in Mexico and other countries in Latin America.1 Cognitive impairment often leads to dementia and it is important to identify modifiable risk factors because a 5-year delay in onset might halve the prevalence of dementia.2 However, nearly all the evidence about potentially modifiable risk factors for cognitive impairment comes from studies in high-income countries.3 Indeed, the authors of the 2020 Lancet Commission on Dementia Prevention, Intervention, and Care concluded that there was an urgent need for more evidence from Latin America.3 Prospective cohort studies suggest that leisure time physical activity is a major modifiable risk factor for cognitive decline and dementia.4 However, to the best of our knowledge, there are no such studies in Latin America. The ‘weekend warrior’ takes part in one or two sessions of sport or exercise per week,5 and it may be particularly important to investigate the benefits of the weekend warrior physical activity pattern in Latin America because lack of time is a major barrier to leisure time physical activity in the region.6–8 Therefore, the main objective of the present analysis was to investigate associations of the weekend warrior physical activity pattern with mild dementia in the Mexico City Prospective Study. Katzmarzyk and colleagues estimated that the burden of dementia attributable to low physical activity was approximately 10% in high-income Western countries and 11% in Latin America and the Caribbean.9 They also calculated that the burden of dementia attributable to low physical activity was approximately 8.5% in Mexico.9 However, Katzmarzyk and colleagues9 used data from outside Mexico to estimate dementia risks.4 Therefore, the secondary objective of the present analysis was to investigate the burden of mild dementia attributable to low leisure time physical activity in Mexico City.
Methods
Participants
The Mexico City Prospective Study is described in detail elsewhere.10 Briefly, door-to-door interviews were conducted from 1995 to 1997 to compile a record of all households in the neighbouring districts of Coyoacán and Iztapalapa in Mexico City in Mexico.10 Recruitment teams then visited households and at least one participant aged 35 years or older was recruited from 94% of eligible households.10 The resulting sample was deemed to be broadly representative of the population aged 35 years or older in Mexico City.10 The baseline survey took place from 1998 to 2004, the re-survey took place from 2015 to 2019, and mortality was tracked to 31 December 2020. The present analysis only includes cohort members who took part in the baseline survey and the re-survey. Trained nurses collected data in the participant’s household and all participants provided written informed consent. The data used in the current report were obtained through an open-access data request made to the Mexico City Prospective Study principal investigators.
Exposure
The exposure was leisure time physical activity, which is a broad term that includes sport and exercise.11–13 During the baseline survey, participants were asked whether they exercised or played sports (yes or no). Those who said ‘yes’ were then asked how many times per week they exercised (less than once per week; once or twice per week; or three or more times per week). Finally, they were asked how many minutes they spent exercising per session (<30; 30–60; or >60). Four exposure groups were created based on the physical activity questions. The ‘no sport or exercise’ group included those who said they did not exercise or play sports. The ‘weekend warrior’ group included those who said they exercised or played sports up to once or twice per week. The ‘regularly active’ group included those who said they exercised or played sports three or more times per week. We have shown that physical activity patterns can change considerably between baseline and re-survey in participants in the Mexico City Prospective Study.14 Therefore, we also included a combined group of weekend warriors and the regularly active. Simple physical activity assessment tools like the one used in the present study have been validated against multiple-item physical activity assessment tools15 and against cardiorespiratory fitness.16 The terms ‘sport’ and ‘exercise’ can have negative connotations in the UK and other Western countries,17 but asking someone what sport they like in Latin America is as innocent a question as asking them what music they like.8
Outcome
The Mini Mental State Examination (MMSE) is probably the most widely used tool to screen for cognitive impairment and dementia in older adults.18 It has a sensitivity of 0.89 (95% CI 0.85 to 0.92) and a specificity of 0.89 (95% CI 0.85 to 0.93).18 The original MMSE19 and the Spanish version used in the present study have the same domains and scores: orientation to time (5 points); orientation to place (5 points); registration (3 points); attention and calculation (5 points); recall (3 points); and language (9 points). Systematic reviews of the literature show that various MMSE cut-offs have been used to define mild cognitive impairment, mild dementia and moderate dementia.18 20 The MMSE was administered at re-survey in the Mexico City Prospective Study and we used cut-offs for mild dementia of ≤22 and ≤23 in the main analyses. The cut-off of ≤22 is recommended in the general population,21 and it has been suggested that the cut-off of ≤23 be considered in older adults in Mexico.22 23 Trained nurses implemented the re-survey questionnaire and assessed medical history. Cohort members who reported a diagnosis of dementia were excluded from the present analysis.
Confounders
Confounders that may influence the relationships between physical activity and cognition include age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol.3 Trained nurses implemented the baseline questionnaire. Participants were asked to report their age and sex. Participants were asked about education and we created five groups (none; at least some elementary; at least some high-school; at least some college; and at least some university). Participants reported their income and we created three groups (tertiles 1, 2 and 3). The nurses asked about smoking and we created three categories (never, former and current). Participants reported their civil status and we created three groups (not married or with partner; married or with partner; widowed). Participants were asked about sleep duration and we defined the at-risk group as sleeping <5 hours or >10 hours per night. Diet quality was expressed as fruit and vegetable intake (never; 1 or 2 days per week; 3 or 4 days per week; ≥5 days per week). The nurses also asked about alcohol drinking frequency and we created four categories (never; occasionally; at least once per week; and daily). At the end of the questionnaire, seated blood pressure was measured using a standard mercury sphygmomanometer and was expressed as the average of three measurements taken at 3 min intervals. Finally, weight and height were measured in light clothing and without shoes and body mass index was expressed as weight in kilograms divided by height in metres squared.
Statistical analyses
Participants’ characteristics at baseline were described according to physical activity patterns. In the main analysis we investigated associations of physical activity patterns at baseline with mild dementia at re-survey. Cox models were created and hazard ratios and 95% CIs were calculated. Models were adjusted for age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline. The proportional hazards assumption was checked graphically for discreet physical activity patterns and no violations were observed. In the secondary analysis we investigated the burden of mild dementia associated with low leisure time physical activity. The attributable fraction for low leisure time physical activity was defined as the proportion of cases of mild dementia that would not exist if all middle-aged adults were to take part in sport or exercise once or twice per week or more often. Attributable fractions were estimated using the methods described by Newson24 and were adjusted for age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline. We also investigated associations between physical activity and mild dementia stratified by sex. Finally, we investigated associations between physical activity and cognition stratified by the alternative MMSE scores of 21–24 for mild dementia and 13–20 for moderate dementia.20 Cohort members who had a history of dementia at re-survey were removed from all analyses to minimise the possibility of reverse causation. All analyses were performed using Stata MP version 15.1 for Mac (StataCorp, Texas, USA).
Patient and public involvement
Patients and other members of the public were not involved in the design or conduct of this study.
Equity, diversity and inclusion
In the Mexico City Prospective Study, door-to-door interviews were conducted in the neighbouring districts of Coyoacán and Iztapalapa, at least one person was recruited from 94% of eligible households, and the final sample was broadly representative of the population aged ≥35 years in Mexico City. The author team includes three men and four women. Six of the authors live and work in Latin America and one author spends their time in both Europe and Latin America. Physical activity levels are reported according to age, sex, education, and income and associations between physical activity and health are adjusted for these important confounders. In the Discussion section we explain why the magnitude of the association between leisure time physical activity and cognitive decline may be different in Latin America and in high-income countries in Europe and North America.
Results
Online supplemental figure S1 shows the flow of participants through the Mexico City Prospective Study. Data from 10 033 of 10 143 (99%) participants in the re-survey were included in the present analysis, after excluding 31 who did not complete the MMSE, 77 who had a history of dementia at re-survey, and two who had missing values for physical activity. Table 1 shows the participants’ characteristics at baseline according to physical activity patterns. The average age was 51 years in those who reported no sport or exercise and was similar in the weekend warriors and the regularly active. The proportion of women was 73% in those who reported no sport or exercise and was lower in the other groups. The proportion with no education was 13% in those who reported no sport or exercise and was only 6% in the weekend warriors and the regularly active. The proportion in the lowest income tertile was 51% in those who reported no sport or exercise, 31% in the weekend warriors and 46% in the regularly active. The proportion who currently smoked was highest in the weekend warriors. Three-quarters of participants were married or with a partner. Three per cent of participants reported sleeping <5 hours or >10 hours per night. The frequency of fruit and vegetable intake tended to be higher in the weekend warriors and higher still in the regularly active. The proportion who drank alcohol at least once a week was highest in the weekend warriors. Systolic blood pressure and body mass index were similar in those who did and did not take part in sport or exercise.
Table 1Characteristics of participants at baseline according to physical activity patterns
| No sport or exercise | Weekend warrior pattern | Regularly active pattern | |
| Number (%) | 7945 (79.19) | 726 (7.24) | 1362 (13.58) |
| Age, years, mean (SD) | 51.1 (10.7) | 49.5 (10.5) | 52.2 (10.8) |
| Sex | |||
| Men, n (%) | 2115 (26.62) | 397 (54.68) | 496 (36.42) |
| Women, n (%) | 5830 (73.38) | 329 (45.32) | 866 (63.58) |
| Education | |||
| None, n (%) | 1029 (12.95) | 45 (6.20) | 84 (6.17) |
| Some elementary, n (%) | 4408 (55.50) | 313 (43.11) | 631 (46.33) |
| Some high-school, n (%) | 1748 (22.01) | 214 (29.48) | 384 (28.19) |
| Some college, n (%) | 382 (4.81) | 66 (9.09) | 110 (8.08) |
| Some university, n (%) | 376 (4.73) | 88 (12.12) | 153 (11.23) |
| Income | |||
| Tertile 1 (lowest), n (%) | 4026 (50.67) | 228 (31.40) | 630 (46.26) |
| Tertile 2, n (%) | 1886 (23.74) | 146 (20.11) | 274 (20.12) |
| Tertile 3 (highest), n (%) | 2033 (25.59) | 352 (48.48) | 458 (33.63) |
| Systolic pressure, mm Hg, mean (SD) | 128 (16) | 127 (15) | 127 (15) |
| Smoking | |||
| Never, n (%) | 4367 (55.01) | 296 (40.77) | 662 (48.68) |
| Former, n (%) | 1271 (16.01) | 162 (22.31) | 295 (21.69) |
| Current, n (%) | 2301 (28.98) | 268 (36.91) | 403 (29.63) |
| Body mass index, kg/m2, mean (SD) | 29.6 (5.0) | 28.4 (4.5) | 28.7 (4.9) |
| Civil status | |||
| Not married or with partner, n (%) | 1153 (14.51) | 108 (14.88) | 200 (14.70) |
| Married or with partner, n (%) | 5987 (75.36) | 547 (75.34) | 1042 (76.56) |
| Widowed, n (%) | 805 (10.13) | 71 (9.78) | 119 (8.74) |
| Sleep duration <5 or >10 hours | |||
| No, n (%) | 7696 (96.87) | 704 (96.97) | 1325 (97.28) |
| Yes, n (%) | 249 (3.13) | 22 (3.03) | 37 (2.72) |
| Fruit and vegetable intake | |||
| Never, n (%) | 76 (0.96) | 1 (0.14) | 8 (0.59) |
| 1 or 2 days per week, n (%) | 1361 (17.13) | 101 (13.91) | 112 (8.22) |
| 3 or 4 days per week, n (%) | 2286 (28.78) | 223 (30.72) | 289 (21.22) |
| ≥5 days per week, n (%) | 4221 (53.13) | 401 (55.23) | 953 (69.97) |
| Alcohol drinking | |||
| Never, n (%) | 1632 (20.54) | 98 (13.50) | 208 (15.27) |
| Occasionally, n (%) | 5889 (74.12) | 558 (76.86) | 1073 (78.78) |
| At least once per week, n (%) | 342 (4.30) | 63 (8.68) | 67 (4.92) |
| Daily, n (%) | 82 (1.03) | 7 (0.96) | 14 (1.03) |
Table 2 shows MMSE scores at re-survey according to physical activity patterns at baseline. The average MMSE score at re-survey was 24.5 in those who reported no sport or exercise at baseline, 25.8 in weekend warriors and 25.6 in the regularly active. The prevalence of mild dementia at re-survey was 26% in those who reported no sport or exercise at baseline, 14% in weekend warriors and 18.5% in the regularly active when defined as an MMSE score of ≤22. The prevalence of mild dementia was 30% in those who reported no sport or exercise at baseline, 20% in weekend warriors and 22% in the regularly active when defined as an MMSE score of ≤23.
Table 2Mini Mental State Examination scores at re-survey according to physical activity patterns at baseline
| Physical activity pattern | |||
| No sport or exercise | Weekend warrior | Regularly active | |
| Number (%) | 7945 (79.19) | 726 (7.24) | 1362 (13.58) |
| MMSE score, mean (SD) | 24.54 (5.71) | 25.85 (4.88) | 25.56 (5.34) |
| MMSE score of ≤22 | |||
| No, n (%) | 5900 (74.26) | 623 (85.81) | 1110 (81.50) |
| Yes, n (%) | 2045 (25.74) | 103 (14.19) | 252 (18.50) |
| MMSE score of ≤23 | |||
| No, n (%) | 5533 (69.64) | 583 (80.30) | 1061 (77.90) |
| Yes, n (%) | 2412 (30.36) | 143 (19.70) | 301 (22.10) |
The baseline surveys took place from 1998 to 2004 and the re-surveys from 2015 to 2019.
MMSE, Mini Mental State Examination.
Table 3 shows associations of physical activity patterns at baseline with cognition at re-survey, where mild dementia was defined as a score of ≤22 on the MMSE. Participants were followed for a mean (SD) of 16.2 (2.1) years and there were 2400 cases of mild dementia during 162 538 person-years of follow-up. Compared with the group that reported no sport or exercise, the hazard ratio for mild dementia was 0.75 (95% CI 0.61 to 0.91) in the weekend warrior group, 0.89 (95% CI 0.78 to 1.02) in the regularly active group and 0.84 (95% CI 0.75 to 0.95) in the combined group of weekend warriors and the regularly active after adjustment for age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline.
Table 3Associations of physical activity patterns at baseline with mild dementia at re-survey using a score of ≤22 on the Mini Mental State Examination
| Physical activity pattern | N/cases (% cases) | Adjusted for age and sex | Fully adjusted |
| No sport or exercise | 7945/2045 (26%) | 1.00 (Reference) | 1.00 (Reference) |
| Weekend warrior | 726/103 (14%) | 0.63 (0.51 to 0.76) | 0.75 (0.61 to 0.92) |
| Regularly active | 1362/252 (18.5%) | 0.72 (0.63 to 0.83) | 0.89 (0.78 to 1.02) |
| Weekend warrior or regularly active | 2088/355 (17%) | 0.69 (0.62 to 0.78) | 0.85 (0.75 to 0.95) |
Values are hazard ratio (95% CI).
The baseline surveys took place from 1998 to 2004 and the re-surveys from 2015 to 2019. The duration of follow-up was mean (SD) 16.2 (2.1) years.
The fully-adjusted model was adjusted for age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline.
Table 4 shows associations of physical activity patterns at baseline with cognition at re-survey, where mild dementia was defined as a score of ≤23 on the MMSE. There were 2856 cases of mild dementia. Compared with the group that reported no sport or exercise, the hazard ratio for mild dementia was 0.87 (95% CI 0.74 to 1.03) in the weekend warrior group, 0.88 (95% CI 0.78 to 1.00) in the regularly active group and 0.88 (95% CI 0.79 to 0.98) in the combined group of weekend warriors and the regularly active after adjustment for confounders.
Table 4Associations of physical activity patterns at baseline with mild dementia at re-survey using a score of ≤23 on the Mini Mental State Examination
| Physical activity pattern | N/cases (% cases) | Adjusted for age and sex | Fully adjusted |
| No sport or exercise | 7945/2412 (30%) | 1.00 (Reference) | 1.00 (Reference) |
| Weekend warrior | 726/143 (20%) | 0.73 (0.62 to 0.87) | 0.87 (0.74 to 1.03) |
| Regularly active | 1362/301 (22%) | 0.74 (0.65 to 0.83) | 0.88 (0.78 to 1.00) |
| Weekend warrior or regularly active | 2088/444 (21%) | 0.74 (0.66 to 0.81) | 0.88 (0.79 to 0.98) |
Values are hazard ratio (95% CI).
The baseline surveys took place from 1998 to 2004 and the resurveys from 2015 to 2019. The duration of follow-up was mean (SD) 16.2 (2.1) years.
The fully-adjusted model was adjusted for age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline.
The population attributable fraction for low leisure time physical activity was estimated while adjusting for age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline. If mild dementia is defined as a score of ≤22 on the MMSE, theoretically 13% (95% CI 5% to 21%) of cases would be eliminated if all middle-aged adults were to take part in sport or exercise once or twice per week or more often. If mild dementia is defined as a score of ≤23, theoretically 10% (95% CI 2% to 18%) of cases would be eliminated if all middle-aged adults were to take part in sport or exercise once or twice per week or more often.
Table 5 shows associations of physical activity patterns at baseline with cognition at re-survey stratified by sex. The hazard ratios were similar in men and women. For example, when mild dementia was defined as a score of ≤22 on the MMSE, the hazard ratio was 0.73 (95% CI 0.51 to 1.03) in men who were weekend warriors and 0.75 (95% CI 0.59 to 0.96) in women who were weekend warriors after adjustment for confounders. Similarly, when mild dementia was defined as a score of ≤23, the hazard ratio was 0.88 (95% CI 0.66 to 1.17) in men who were weekend warriors and 0.87 (95% CI 0.70 to 1.07) in women who were weekend warriors. The confidence intervals were wider in the stratified analyses because the sample sizes were smaller than in the main analyses.
Table 5Associations of physical activity patterns at baseline with mild dementia at re-survey stratified by sex
| Physical activity pattern | Men | Women | ||
| N/cases (% cases) | HR | N/cases (% cases) | HR | |
| MMSE score of ≤22 | ||||
| No sport or exercise | 2093/507 (24%) | 1.00 (Reference) | 5798/1520 (26 %) | 1.00 (Reference) |
| Weekend warrior | 394/35 (9%) | 0.73 (0.51 to 1.03) | 329/68 (21%) | 0.75 (0.59 to 0.96) |
| Regularly active | 494/86 (17%) | 0.82 (0.65 to 1.04) | 862/164 (19%) | 0.91 (0.78 to 1.01) |
| Weekend warrior or regularly active | 888/121 (14%) | 0.79 (0.65 to 0.97) | 1191/232 (19.5%) | 0.86 (0.75 to 0.99) |
| MMSE score of ≤23 | ||||
| No sport or exercise | 2093/606 (29%) | 1.00 (Reference) | 5798/1784 (31%) | 1.00 (Reference) |
| Weekend warrior | 394/53 (13%) | 0.88 (0.66 to 1.17) | 329/90 (27%) | 0.87 (0.70 to 1.07) |
| Regularly active | 494/102 (21%) | 0.81 (0.65 to 1.00) | 862/196 (23%) | 0.91 (0.79 to 1.06) |
| Weekend warrior or regularly active | 888/155 (17%) | 0.83 (0.69 to 1.00) | 1191/286 (24%) | 0.90 (0.79 to 1.02) |
Values are hazard ratio (95% CI).
The models were adjusted for age, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline.
MMSE, Mini Mental State Examination.
Table 6 shows associations of physical activity patterns at baseline with cognition at re-survey stratified by the alternative MMSE scores of 21–24 for mild dementia and 13–20 for moderate dementia. There was little evidence that physical activity was associated with mild dementia when a range of MMSE scores was used to define the condition, but there was some evidence that physical activity was associated with moderate dementia when a range of scores was used to define the condition. For example, compared with the group that reported no sport or exercise, the hazard ratio for moderate dementia was 0.69 (95% CI 0.53 to 0.92) in the weekend warrior group and 0.83 (95% CI 0.71 to 0.98) in the combined group of weekend warriors and the regularly active after adjustment for confounders.
Table 6Associations of physical activity patterns at baseline with cognition at re-survey stratified by the alternative MMSE scores for mild and moderate dementia
| Physical activity pattern | N/cases (% cases) | HR |
| MMSE score of 21–24 for mild dementia | ||
| No sport or exercise | 6427/1339 (21%) | 1.00 (Reference) |
| Weekend warrior | 653/111 (17%) | 1.13 (0.93, to1.38) |
| Regularly active | 1187/189 (16%) | 0.93 (0.80 to 1.09) |
| Weekend warrior or regularly active | 1840/300 (16%) | 1.00 (0.88 to 1.14) |
| MMSE score of 13–20 for moderate dementia | ||
| No sport or exercise | 6250/1162 (19%) | 1.00 (Reference) |
| Weekend warrior | 595/53 (9%) | 0.69 (0.53 to 0.92) |
| Regularly active | 1128/130 (11.5%) | 0.91 (0.75 to 1.09) |
| Weekend warrior or regularly active | 1723/183 (11%) | 0.83 (0.71 to 0.98) |
Values are hazard ratio (95% CI).
The models were adjusted for age, sex, education, income, systolic blood pressure, smoking, body mass index, civil status, sleep duration, fruit and vegetable intake and alcohol at baseline.
MMSE, Mini Mental State Examination.
Discussion
The main objective of this study was to investigate associations of the weekend warrior physical activity pattern with mild dementia in adults in Mexico City. We found that the weekend warrior physical activity pattern and the regularly active physical activity pattern were associated with similar reductions in mild dementia risks after adjustment for confounders. The secondary objective was to investigate the burden of mild dementia attributable to low leisure time physical activity. We found that around 10% of cases would be eliminated if all middle-aged adults were to take part in sport or exercise once or twice per week or more often. To the best of our knowledge, this is the first prospective cohort study to show that the weekend warrior physical activity pattern is associated with reduced risk of mild dementia.
Novelty and importance
Prospective cohort studies in Africa, East Asia and Pacific, Europe and North America suggest that leisure time physical activity is a major modifiable risk factor for cognitive decline and dementia.4 Overall, compared with the inactive, the odds ratio for cognitive decline was 0.67 (95% CI 0.55 to 0.78) and the odds ratio for dementia was 0.79 (95% CI 0.69 to 0.88) in the physically active.4 Consistency of association is a fundamental consideration in epidemiology25; however, to the best of our knowledge, this is the first prospective cohort study in Latin America to suggest that leisure time physical activity is associated with reduced risk of mild dementia. If it is assumed that odds ratios and hazard ratios are similar measures when risks are closer to 1.0 than 2.5,26 then it is noteworthy that the reduction in risk of cognitive decline was greater in other studies than in the present study.4 These differences in risk may be explained by the high amounts of non-exercise physical activity that are part of everyday life in many cities in Latin America.27–29 For example, if the non-exercise group were to take part in large amounts of walking for transport in Latin America, then the difference in risk between the exercise and non-exercise groups would not be as great as in other regions. It is encouraging that the weekend warrior group, the regularly active group and the combined group were associated with reduced risks in the present study because physical activity patterns may change over time.14 For example, we found that, among cohort members who reported being weekend warriors at baseline, 21% reported being regularly active at re-survey.14 Similarly, among cohort members who reported being regularly active at baseline, 6% reported being weekend warriors at re-survey.14 It is plausible that physical activity improves brain health and several potential mechanisms have been identified.30–35 For example, exercise may increase brain-derived neurotrophic factor concentrations and brain plasticity.30 Physical activity is also associated with greater brain volume, greater executive function and greater memory.31
Policy implications
Cross-sectional studies in Europe36 and North America37 suggest that the weekend warrior physical activity pattern is associated with mental health benefits. For example, Hamer and colleagues found that, compared with the inactive, the odds ratio for psychological distress was 0.68 (95% CI 0.63 to 0.73) in weekend warriors and 0.68 (95% CI 0.64 to 0.72) in the regularly active in the UK.36 To the best of our knowledge, the present study is the first prospective cohort study to show that the weekend warrior physical activity pattern and the regularly active physical activity pattern are associated with similar reductions in the risk of mild dementia. The present study has important implications for policy and practice because the weekend warrior physical activity pattern may be a more convenient option for busy people in Latin America6–8 and elsewhere.5 38 It is particularly encouraging that the weekend warrior physical activity pattern was associated with reduced risk of mild dementia in both men and women in the present study because lack of time is a major barrier to leisure time physical activity in men and women around the world.6–8 In Latin America, as many as eight out of 10 adults say they would like to do more sport,8 and it is reasonable to suggest that more men and women in the region would exercise if they knew that taking part in one or two sessions per week was associated with considerable cognitive health benefits. Hundreds of cities in Latin America provide a free-of-charge physical activity intervention every weekend that is known as the Ciclovía Recreativa.39–41 In Mexico City, for example, more than 50 km of roads are closed to motor vehicles on Sundays and the streets fill with around 80 000 walkers, runners and cyclists.42 43 Sunday is the ideal day for the Ciclovía Recreativa because many people in Mexico and elsewhere in Latin America work long hours from Monday to Saturday.44 Indeed, most participants say they would not exercise if it were not for the Ciclovía Recreativa.42 45 In Mexico alone, the cost of dementia is around US$ 3776 million per year.46 If it is assumed that mild dementia leads to dementia and that the attributable fraction for low leisure time physical activity is around 10%, as suggested in the present study, then around US$ 377.6 million per year would be saved if all middle-aged adults were to take part in sport or exercise once or twice per week or more often. The human and economic costs of mild dementia and dementia suggest that more could be done to promote the Ciclovía Recreativa and other successful physical activity interventions in Mexico.
Strengths and limitations
This study has strengths and limitations. All analyses were adjusted for major confounders3 and cohort members with a history of dementia at re-survey were removed to minimise the possibility of reverse causation. The relatively long follow-up period also makes reverse causation unlikely.3 Creating large samples and obtaining high response rates are among the main goals of data collection in cohort studies.47 The Mexico City Prospective Study is deemed to be broadly representative of the population aged ≥35 years by virtue of the large sample size of more than 150 000 adults and the high response rate of at least one participant from more than 94% of eligible households.10 However, it is not clear whether the original survey or the re-survey are representative because recruitment was not stratified according to demographic parameters such as age, gender or socioeconomic status. Physical activity, dementia history and other variables were self-reported, which may introduce bias. Questionnaires were used to assess physical activity, but it is preferable to use both questionnaires and accelerometers to assess physical activity in cohort studies because each method has advantages and disadvantages.48–50 For example, questionnaires might best be used to identify types of sport and exercise and accelerometers might best be used to assess volumes of physical activity. English and Spanish versions of the MMSE are valid screening tools,23 51 but they are not clinical diagnoses of cognitive impairment or dementia. The sample size in the combined group of weekend warriors and the regularly active in the main analyses was large enough to give precise estimates of the associations between physical activity and mild dementia, as indicated by the relatively narrow confidence intervals. However, larger samples of weekend warriors and larger samples of the regularly active may be required to give more precise estimates of risk in future studies. Larger sub-samples of men and women may also be required to give more precise estimates of risk. There was little evidence that physical activity was associated with mild dementia and some evidence that physical activity was associated with moderate dementia when ranges of MMSE scores were used to define the conditions. However, these data should be treated with some caution because there is a greater risk of misclassification when several categories are used rather than a single cut-off (using the three categories of referent, mild and moderate, there are four possible misclassifications of one category higher or lower than the correct category and six possible misclassifications of one or two categories higher or lower than the correct category).52 Future studies should also include continuous measures of cognition because statistical power is increased when continuous variables are used rather than categorical variables.
Conclusions
To the best of our knowledge, this is the first prospective cohort study to show that the weekend warrior physical activity pattern and the regularly active physical activity pattern are associated with similar reductions in the risk of mild dementia. This study has important implications for policy and practice because the weekend warrior physical activity pattern may be a more convenient option for busy people around the world.
We thank everyone who took part in the study.
Data availability statement
Data are available upon reasonable request. Mexico City Prospective Study data are available for open-access data requests. The data access policy is described online: http://www.ctsu.ox.ac.uk/research/mcps.
Ethics statements
Patient consent for publication
Not applicable.
Ethics approval
The study was approved by the Mexican Ministry of Health, the Mexican National Council of Science and Technology (approval number 0595 P-M), and the Central Oxford Research Ethics Committee (C99.260). Participants gave informed consent to participate in the study before taking part.
X @Fanny_Petermann, @caroochoa_r
Contributors GO'D: conceptualisation, formal analysis, writing the original draft and editing the drafts. FP-R, GF, CM, CO-R, OLLS, and AI: reviewing and editing. GO'D is guarantor.
Funding This research has been conducted using Mexico City Prospective Study (MCPS) data under Application Number 2022-015. MCPS (https://www.ctsu.ox.ac.uk/research/mcps) has received funding from the Mexican Health Ministry, the National Council of Science and Technology for Mexico, Wellcome and core grants from the UK Medical Research Council to the MRC Population Health Research Unit at the University of Oxford. An unauthorized version of the Spanish MMSE was used by the MCPS study team without permission. The MMSE is a copyrighted instrument and may not be used or reproduced in whole or in part, in any form or language, or by any means without written permission of Psychological Assessment Resources, Inc (PAR). AI is partially supported by grants from ANID/FONDECYT Regular (1210195 and 1210176 and 1220995); ANID/FONDAP/15150012; ANID/PIA/ANILLOS ACT210096; FONDEF ID20I10152, ID22I10029; ANID/FONDAP 15150012; Takeda CW2680521 and the MULTI-PARTNER CONSORTIUM TO EXPAND DEMENTIA RESEARCH IN LATIN AMERICA (ReDLat, supported by Fogarty International Center (FIC) and National Institutes of Health, National Institutes of Aging (R01 AG057234, R01 AG075775, R01 AG21051, CARDS-NIH), Alzheimer’s Association (SG-20-725707), Rainwater Charitable foundation–Tau Consortium, the Bluefield Project to Cure Frontotemporal Dementia, and Global Brain Health Institute)). The contents of this publication are solely the responsibility of the authors and do not represent the official views of these institutions. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.
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