The association of last meal timing and the quality of dinner with sleep quality: a cross-sectional study on Iranian adults

This study aimed to investigate the association between the timing and quality of the last meal and sleep quality among Iranian adults. In this cross-sectional study, healthy Iranian adults were included. Dietary intake and meal timing were assessed using three non-consecutive 24-h dietary recalls to calculate the interval between the last meal and bedtime. Dinner quality was evaluated using the NRF9·3 index, and sleep quality was measured using the Pittsburgh Sleep Quality Index. Multivariable logistic and ordinal regressions assessed associations of meal timing and dinner quality with sleep outcomes, adjusting for confounders. The study included 450 adults (mean age: 38·1 ( sd 9·7) years), of whom 55·8 % had good sleep quality. The mean interval between the last meal and sleep was 2·38 ( sd 1·08) h. A longer interval between the last meal and bedtime was associated with higher odds of poor global sleep quality (OR = 2·03, 95 % CI: 1·24, 3·32; P = 0·005). Longer intervals were significantly associated with better subjective sleep quality, shorter sleep latency, longer sleep duration and higher habitual sleep efficiency. Dinner quality demonstrated a mixed pattern of association with sleep quality, showing higher odds of poor sleep in the second tertile (OR = 1·66, 95 % CI: 1·01, 2·73), whereas this association was not observed in the highest tertile (OR = 1·24, 95 % CI: 0·75, 2·04). In conclusion, longer dinner-to-bedtime intervals may improve specific sleep quality aspects, though results remain inconsistent. Further research is essential to clarify these associations and determine optimal meal timing.