Air toxics and late-life dementia and cognitive impairment in Mexican Americans.

BACKGROUND

Air pollution has been linked to cognitive impairment, yet studies on air toxics - specific components of particulate matter and/or volatile organic compounds - remain limited compared to criteria pollutants.

OBJECTIVE

We aim to examine whether long-term exposure to modeled traffic-related and industrial/urban-related air toxics including benzene, 1,3-butadiene, lead, nickel, chromium, zinc was associated with the development of incident dementia or cognitive impairment without dementia (CIND) among older Mexican Americans.

METHODS

We included 1612 Mexican American participants from the Sacramento Area Latino Study on Aging conducted from 1998 to 2007. Land use regression models estimated concentrations of annual air toxics based on the participants' geocoded residential addresses. Using Cox proportional hazard models, we estimated the hazard of incident dementia or CIND for time-varying air toxics exposures calculated by averaging over 1-, 3-, 5- and 10-calendar years prior to an event for everyone in the risk set at the event time; pollutant concentrations were entered into models as continuous variables scaled by their inter-quartile range (IQR).

RESULTS

Among the air toxics, higher 1,3-butadiene levels we estimated a hazard ratio of 1.12 (95 % CI: 1.00, 1.25) for incident dementia/CIND per IQR increase in 1,3-butadiene exposures. Benzene, zinc and nickel were positively and more strongly associated with dementia/CIND or dementia alone, but the estimated 95 % confidence intervals crossed the null. Associations remained robust when adjusting for other co-pollutants.

CONCLUSION

Our findings indicate that air toxics are adversely associated with cognition in older Mexican Americans, providing critical evidence that traffic- and industry-related air toxics contribute to cognitive impairment. Future studies exploring the mechanisms underlying these associations are needed.