Obesity, apolipoprotein E ε4 and difficulties in activities of daily living among older adults: A six-year follow-up study

Background
Obesity has been associated with increased physical limitations among older adults, although few studies have adjusted for important covariates. There is limited information about the relationship between apolipoprotein E (APOE) polymorphisms and physical limitations, and the findings have been inconsistent.
Purpose
This study examined the longitudinal associations of obesity and APOE ε4 with difficulties in activities of daily living (ADLs) over a 6-year follow-up period controlling for multiple covariates.
Methods
Data were analyzed from the Social Environment and Biomarkers of Aging Study (SEBAS) in Taiwan collected in 2000 and 2006, involving a cohort of 639 participants (mean age = 66). Body mass index (BMI) was used to define obesity at a baseline, and the APOE genotype was classified into an APOE ε4 carrier and non-carrier status. The combination of basic and instrumental activities of daily living (ADLs and IADLs) was used to define impaired ADLs.
Results
APOE ε4 carriers had greater difficulties in combined ADLs (incident rate ratio; IRR = 1.87, 95 % CI = 1.40–2.51) than non-carriers. Obese but not overweight adults had greater difficulties in activities of daily living (IRR = 1.59, 95 % CI = 1.20–2.10) compared with the normal/underweight group. Obese older adults without APOE ε4 had greater subsequent difficulties in ADLs than non-obese non-carriers. Among APOE ε4 carriers, obesity was not a significant risk factor for the development of impaired ADLs in older adults, indicating an interaction between genotype and obesity.
Conclusions
The interaction between genotype and obesity phenotype adds new information about the determinants of physical impairment.