The association between modified Nordic diet with sleep quality and circadian rhythm in overweight and obese woman: a cross-sectional study

Objective: Previous studies have shown an association between diet quality and sleep quality. The objective of this study was to investigate the association between modified Nordic diet with sleep quality and circadian rhythm in overweight and obese woman. Methods: We enrolled 399 overweight and obese women (body mass index (BMI): 25–40 kg/m²), aged 18–48 years, in this cross-sectional study. For each participant, anthropometric measurements, biochemical tests, and food intake were evaluated. Sleep quality and circadian rhythm was measured by Pittsburgh Sleep Quality Index (PSQI) and morning–evening questionnaire (MEQ) questionnaire. Modified Nordic diet score was measured using a validated 147-item food frequency questionnaire (FFQ). Results: Overall, 51.7% of the subjects were good sleepers (the Pittsburgh Sleep Quality Index (PSQI) < 5) while 48.3% were poor sleepers (PSQI ≥ 5). Moreover, participants were divided into five groups of MEQ, namely, completely morning 8 (2.4%), rarely morning 82 (24.8%), normal 196 (59.2%), rarely evening 43 (13%), and completely evening 2 (0.6%). After controlling for confounders, there was a significant association between poor sleep quality and the modified Nordic diet (OR = 0.80, %95 CI = 0.66–0.98, P = 0.01). Moreover, a significant positive association was observed between the completely morning and modified Nordic diet (OR = 1.80, %95 CI = 0.54–6.00, P = 0.03), in addition to a significant inverse association between the completely evening type and modified Nordic diet (OR = 0.16, %95 CI = 0.002–5.41, P = 0.02). Conclusions: The present study indicated that higher adherence to a modified Nordic diet reduces poor sleep quality. Also, the completely morning type was associated with higher adherence to a modified Nordic diet, and completely evening type was associated with lower adherence to a modified Nordic diet. Levels of evidence: Level IV, evidence obtained from multiple time series analysis.