Association of Rest-Activity Rhythm and Sleep Regularity With Cardiometabolic Disease in the CAR

• This cross-sectional analysis from the CARDIA sleep ancillary study (2020–2023) investigates whether rest–activity rhythms and sleep regularity relate to cardiometabolic disease markers, with examination of potential racial differences between Black and White participants.

• Population: 861 participants with actigraphy data for seven days, comprising 354 Black and 507 White individuals.
• Rhythm metrics: Sleep Regularity Index; rest–activity rhythm indices including interdaily stability, intradaily variability, relative amplitude; and start times for the most active 10-hour and least active 5-hour periods.
• Cardiometabolic markers: body mass index (BMI), waist circumference, blood pressure metrics, hypertension status, fasting glucose, estimated insulin resistance, and diabetes status.

• Linear regression models with interaction terms assessed whether associations differed by race.
• Primary focus on the strength and direction of relationships between rhythmic measures and anthropometric, glycemic, and blood pressure markers.

The direction and magnitude aligned with weaker rhythms corresponding to higher BMI.

Similar patterns emerged for waist circumference.

• Anthropometric associations: Most rest–activity indices, aside from the most active 10-hour start, and the Sleep Regularity Index, showed associations with BMI.
• Race-specific patterns: Some effect modification by race was evident, particularly for relative amplitude’s association with BMI, stronger in White participants (notably: White β ≈ −2.63 versus Black β ≈ −1.24).
• Glycemic markers: Disrupted circadian indices tended to associate with glycemic measures, with findings generally consistent across race groups.
• Blood pressure: Associations between rest–activity rhythms and blood pressure were less consistent overall and across racial subgroups.

• The data suggest weaker rest–activity rhythms and irregular sleep relate to less favorable anthropometric and glycemic profiles, with limited and inconsistent links to blood pressure and only modest racial differences.
• The cross-sectional design limits causal inference, and several metrics showed variable strength across outcomes and racial strata.