Abstract Body: Introduction: Emerging evidence suggests that diet also influences sleep health. Dairy intake may impact sleep but few studies have evaluated the association between dairy consumption and sleep health. We evaluated the association between dairy consumption (total and subtypes) and sleep outcomes cross-sectionally and longitudinally in a French population.

Hypothesis: Participants with higher dairy intakes will have better sleep outcomes compared to those with lower intakes.

Methods: We studied 37,396 adults from the NutriNet-Santé e-cohort (mean age 49.9±14.8 y). Dairy product intake was estimated at baseline (2014) from at least two 24-h dietary recalls and stratified as low, moderate, or high based on average intake. Trouble sleeping, chronic insomnia, and acute insomnia were assessed at baseline and follow-up (2023). Total sleep time (TST) was estimated from sleep logs at baseline. We fit multivariate logistic regression models adjusted for sociodemographics, anthropometrics, lifestyle behaviors, sugar and saturated fat intakes, and diet quality to estimate the odds ratio (OR) of sleep health associated with dairy consumption.

Results: In cross-sectional analyses, participants with high total dairy intake had 6% higher odds of acute insomnia, compared to those with low intake (OR_{high vs low}=1.06; 95% CI 1.00-1.12; P-trend=0.042). High intake of yogurt-like products (e.g. yogurts, curd cheese and petit-suisses) was associated with higher odds of trouble sleeping (OR_{high vs low}=1.07; 95% CI 1.02-1.13; P-trend=0.013), chronic insomnia (OR_{high vs low}=1.08; 95% CI 1.01-1.15; P-trend=0.027), and acute insomnia (OR_{high vs low}=1.13; 95% CI 1.08-1.19; P-trend<0.0001), but lower odds of long TST (OR_{high vs low}=0.79; 95%CI 0.70-0.88; P-trend<0.0001). Similar associations for TST were observed for high fermented dairy (e.g., cheese and yogurt) (P-trend=0.0006) and high-fat dairy (P-trend=0.0072) intakes. In longitudinal analyses, trends in the opposite direction were noted for chronic insomnia (P-trend range: 0.064–0.994).

Conclusions: Our findings suggest that certain dairy products may be associated with poorer sleep outcomes in cross-sectional analyses; however, these associations did not predict sleep quality long-term. It is possible that individuals with sleep difficulties increased their dairy intake to improve sleep. Clinical interventions are warranted to confirm findings, address causality, and accurately inform dietary guidelines for sleep health.