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) epsilon 4, 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 epsilon 4 carriers or diabetics with low levels of PA compared with epsilon 4 noncarriers or nondiabetics who engaged in high PA (epsilon 4: 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 epsilon 4 carriers and those who have diabetes. (C) 2017 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.