Physical activity modifies the influence of apolipoprotein E ε4 allele and type 2 diabetes on dementia and cognitive impairment among older Mexican Americans.

INTRODUCTION

The etiologies of dementia are complex and influenced by genetic and environmental factors including medical conditions.

METHODS

We used Cox regression model to estimate the individual and joint effects of physical activity (PA), apolipoprotein E (APOE) ε4, and diabetes status on risk of dementia and cognitive impairment without dementia (CIND) among 1438 cognitively intact Mexican American elderly who were followed up to 10 years.

RESULTS

The risk of developing dementia/CIND was increased more than threefold in APOE ε4 carriers or diabetics with low levels of PA compared with ε4 noncarriers or nondiabetics who engaged in high PA (ε4: hazard ratio [HR] = 3.44, 95% confidence interval [CI] = 1.85-6.39; diabetes: HR = 3.11, 95% CI = 1.87-5.18); the presence of all three risk factors increased risk by nearly 10-fold (HR = 9.49, 95% CI = 3.57-25.3).

DISCUSSION

PA in elderly Hispanics protects strongly against the onset of dementia/CIND, especially in APOE ε4 carriers and those who have diabetes.