Sleep Irregularity and Short Sleep Duration Are Associated with Less Favorable Cardiometabolic Profiles in Healthy Adults: A Cross-Sectional Study

Background/Objectives: The aim of this study is to evaluate the relation between sleep quantity (TST), efficiency (SE) and regularity (SRI) and cardiometabolic parameters and eating habits. Methods: Seventy clinically healthy adults (74% females; mean age 28.3 ± 10.1 years) were recruited at the Clinical Nutrition Unit of Careggi University Hospital, Florence, between October 2023 and December 2024. Sleep was monitored for 7 days using a Fitbit Alta HR actigraphy. Cardiometabolic health was assessed via bioimpedance and blood samples. Dietary habits were evaluated through 3-day food diaries and the Medi-Lite questionnaire. Results: Participants had an average TST of 7.4 ± 1.1 h, SE of 84.9 ± 6.9%, and SRI of 62.2 ± 19.9. Lower SRI (≤41, 1st quintile) was associated with higher fat mass (19.9 ± 6.7 vs. 15.2 ± 6.6%), higher total cholesterol (183.9 ± 20.9 vs. 155.0 ± 26.8 mg/dL), and lower folate (3.6 ± 1.6 vs. 5.6 ± 2.5 ng/mL) compared to higher SRI (≥80, 5th quintile). Sleeping <7 h/night was linked to higher BMI (22.6 ± 2.1 vs. 21.5 ± 2.0 kg/m2) and homocysteine (11.4 ± 2.3 vs. 10.4 ± 3.3 μmol/L). Weak but significant inverse correlations emerged between TST and BMI (R = −0.26, p = 0.02) and between SRI and cholesterol (R = −0.28, p = 0.01), but these associations disappeared in the multivariable linear regression adjusted model. Conclusions: These findings underscore the role of sleep duration and regularity in shaping body composition and cardiometabolic health, supporting its relevance as a modifiable public health priority.