A national case-crossover analysis of the short-term effect of PM2.5 on hospitalizations and mortality in subjects with diabetes and neurological disorders

Abstract

Doc number: 38

Abstract

Background: Diabetes and neurological disorders are a growing burden among the elderly, and may also make them more susceptible to particulate air matter with aerodynamic diameter less than 2.5 μg (PM_2.5 ). The same biological responses thought to effect cardiovascular disease through air pollution-mediated systemic oxidative stress, inflammation and cerebrovascular dysfunction could also be relevant for diabetes and neurodegenerative diseases.

Methods: We conducted multi-site case-crossover analyses of all-cause deaths and of hospitalizations for diabetes or neurological disorders among Medicare enrollees (>65 years) during the period 1999 to 2010 in 121 US communities. We examined whether 1) short-term exposure to PM_2.5 increases the risk of hospitalization for diabetes or neurological disorders, and 2) the association between short-term exposure to PM_2.5 and all-cause mortality is modified by having a previous hospitalization of diabetes or neurological disorders.

Results: We found that short term exposure to PM_2.5 is significantly associated with an increase in hospitalization risks for diabetes (1.14% increase, 95% CI: 0.56, 1.73 for a 10 μg/m³ increase in the 2 days average), and for Parkinson's disease (3.23%, 1.08, 5.43); we also found an increase in all-cause mortality risks (0.64%, 95% CI: 0.42, 0.85), but we didn't find that hospitalization for diabetes and neurodegenerative diseases modifies the association between short term exposure to PM_2.5 and all-cause mortality.

Conclusion: We found that short-term exposure to fine particles increased the risk of hospitalizations for Parkinson's disease and diabetes, and of all-cause mortality. While the association between short term exposure to PM_2.5 and mortality was higher among Medicare enrollees that had a previous admission for diabetes and neurological disorders than among Medicare enrollees that did not had a prior admission for these diseases, the effect modification was not statistically significant. We believe that these results provide useful insights regarding the mechanisms by which particles may affect the brain. A better understanding of the mechanisms will enable the development of new strategies to protect individuals at risk and to reduce detrimental effects of air pollution on the nervous system.