APOE genotype status on the effect of residential greenness on cognitive function and mortality: a cohort study

Background Our study aimed to test whether the effects of residential greenness on cognitive function and mortality differ by APOE genotypes among Chinese adults aged 65 years and older. Methods We used Chinese Longitudinal Healthy Longevity Survey data, a longitudinal cohort of individuals aged 65 years and older. We calculated the normalised difference vegetation index (NDVI) using a 500 m radius around each participant's residence to reflect residential greenness. We used the Mini-Mental State Examination (MMSE) to measure cognitive function, and monitored survival status between 2000 and 2014. We categorised participants as APOE ɛ2 carriers, ɛ3/ɛ3 carriers, and ɛ4 carriers. We applied logistic regression to examine the association between baseline annual average NDVI, APOE genotypes, and cognitive impairment (reference group MMSE ≥24), and the Cox proportional hazard regression to assess the relationship between contemporaneous NDVI, APOE genotypes, and mortality. We adjusted for age, sex, ethnicity, marital status, urban or rural residence, education, occupation, financial status, social and leisure activity, smoking status, drinking status, physical activity, and geographic regions. Findings We included 9156 participants with a mean age of 82·6 years (SD 11·8). 1302 (14·2%) participants were APOE ɛ2 carriers, 6254 (68·3%) were ɛ3/ɛ3 carriers, and 1600 (17·5%) were ɛ4 carriers. We observed a significant interaction between NDVI and APOE genotypes both for cognitive impairment (pinteraction=0·0025) and mortality (pinteraction Interpretation Our finding elucidates possible gene-environment interaction mechanisms in which residential greenness might protect against cognitive impairment and mortality among older adults. Our study provides evidence of possible gene-environment interaction. Funding None.