Moderating role of nutrition knowledge on the association between residential fast-food restaurant exposure and diet among urban-dwelling older adults

Objective: To assess the moderating role of nutrition knowledge on the relation between the availability of residential-area fast-food restaurant and healthful diet among seniors in Montreal. Methods: Data from 748 adults from the Quebec Longitudinal Study on Nutrition and Healthy Aging were merged with food source data in a GIS. A “prudent diet” score reflecting diet quality was estimated from principal components analysis on food-frequency questionnaire data. A “relative availability” measure of density of fast-food outlets (FFO) relative to all restaurants was calculated for 500m buffers around participants' homes. Nutrition knowledge was summed from a nine item, 5-point Likert scale (α=0.82) and expressed (by tertiles) as weaker, average, and greater knowledge. Main and interactive effects of knowledge and relative availability of FFOs were tested using linear regression analyses accounting for individual-level (health and socio-demographic) and area-level (socioeconomic and ethnicity) covariates. Results: Average and weaker nutrition knowledge was associated with lower prudent diet scores (βstd= -0.13; p=0.003 and βstd= -0.25; p<0.001 respectively). The relative availability of FFOs was inversely associated with prudent diet scores, but only for the weaker nutrition knowledge category (βstd= -0.13; p=0.01).