Neighbourhood exposure to fast-food and sit-down restaurants and estimated 24-hour urinary sodium excretion: a cross-sectional analysis of urban adults from the ORISCAV-LUX 2 study.

Objective: Increased out-of-home consumption may elevate sodium (Na) intake, but self-reported dietary assessments limit evidence. This study explored associations between neighbourhood exposure to fast-food and sit-down restaurants and estimated 24-hour urinary Na excretion.

Design: A cross-sectional analysis from the ORISCAV-LUX 2 study (2016-2017). 24-hour urinary Na was estimated from a morning spot urine sample using the INTERSALT formula. Spatial access to fast-food and sit-down restaurants was derived from GIS data around participants' addresses within 800-m and 1000-m road network buffers by summing up the inverse of the road network distance between their residential address and all restaurants within the corresponding buffer size. Multi-adjusted linear models were used to assess the association between spatial access to restaurants and estimated 24-hour urinary Na excretion.

Setting: Luxembourg.

Participants: Urban adults age over 18 years (n 464).

Results: Fast-food and sit-down restaurants accounted for 58·5 % of total food outlets. Mean 24-hour urinary Na excretion was 3564 mg/d for men and 2493 mg/d for women. Health-conscious eating habits moderated associations between spatial access to fast-food and sit-down restaurants and Na excretion. For participants who did not attach great importance to having a balanced diet, greater spatial access to restaurants, combining both density and accessibility, was associated with increased urinary Na excretion at 800 m (β_highvslow = 259, 95 % CI: 47, 488) and 1000 m (β_highvslow = 270, 95 % CI: 21, 520).

Conclusions: Neighbourhood exposure to fast-food and sit-down restaurants influences Na intake, especially among individuals with less health-conscious eating habits, potentially exacerbating diet-related health disparities.