Nitrogen dioxide exposure attenuates or even reverses the association between physical activity and fasting plasma glucose levels in non-diabetic elderly Chinese adults

Abstract

Background

The combined effects of physical activity (PA) and nitrogen dioxide (NO₂) on fasting plasma glucose (FPG) levels have rarely been studied. This study aimed to examine whether long-term exposure to NO₂ attenuates the association between PA and FPG levels in non-diabetic older adults.

Methods

A total of 2600 non-diabetic elderly Chinese adults were included in this cross-sectional study. PA data were collected using the International Physical Activity Questionnaire (IPAQ). The Space-Time Extra-Trees model was utilized to estimate the annual concentration of NO₂. General linear regression models were used to assess independent and interaction associations of long-term exposure to NO₂ and PA with FPG levels. An interaction plot was employed to enhance the visual representation of the interaction.

Results

A 0.32 µg/m³ increase in the 3-year average NO₂, corresponding to one interquartile range (IQR), was positively associated with FPG levels (β = 0.099 mmol/L, 95% CI: 0.069–0.130). PA exhibited a negative, albeit non-significant, association with FPG levels (β = -0.027 mmol/L, 95% CI: -0.069, 0.015). A statistically significant interaction between PA and NO₂ on FPG levels was observed (P_{for interaction} = 0.016). The interaction plots revealed that the beneficial effects of PA on FPG levels were attenuated or even reversed as NO₂ concentrations increased, with a threshold for reversal at 33.02 µg/m³.

Conclusions

Long-term exposure to NO₂ attenuates or reverses the beneficial effects of PA on FPG levels in non-diabetic older adults. Therefore, further action is imperative to reduce air pollution and thereby enhance the benefits of PA on FPG levels.