The Canadian Study of Health and Aging: risk factors for Alzheimer's disease in Canada.

OBJECTIVE

To study risk factors for Alzheimer's disease (AD) based on data from the Canadian Study of Health and Aging.

DESIGN

Population-based case-control study.

SETTING

Communities and institutions in 10 Canadian provinces.

PARTICIPANTS

Two hundred fifty-eight cases clinically diagnosed with probable AD, with onset of symptoms within 3 years of diagnosis, and 535 controls, frequency matched on age group, study center, and residence in community or institution, clinically confirmed to be cognitively normal.

MAIN OUTCOME MEASURE

Odds ratios (ORs) were calculated using unconditional logistic regression for previously hypothesized and potential risk factors for AD.

RESULTS

The OR for family history of dementia was significantly elevated (2.62; 95% confidence interval [CI], 1.53 to 4.51) and increased with the number of relatives with dementia. Those with less education were at higher risk of AD, with an OR of 4.00 (95% CI, 2.49 to 6.43) for those with 0 to 6 years, in comparison with those with 10 or more years. Head injury achieved borderline significance. A history of arthritis resulted in a low risk of AD (OR = 0.54; 95% CI, 0.36 to 0.81), as did a history of use of nonsteroidal anti-inflammatory drugs. Initial analyses showed an increased risk of AD for occupational exposure to glues as well as to pesticides and fertilizers; the increased risk was greater in those with less education.

CONCLUSION

This study confirmed a number of previously reported risk factors for AD, but provided little support for others. A new finding was an increased risk for those with occupational exposure to glues as well as pesticides and fertilizers, but this needs further study.