The interaction between exercise and sleep with heart rate variability: cross-sectional study.

Purpose: To examine whether the interaction between exercise intensity and sleep duration/quality is associated with heart rate variability (HRV).

Methods: A sample of 391 adults (M_age = 57 years) from the Midlife in the United States Biomarker study 2004-2009 provided sleep actigraphy, electrocardiogram (ECG) HRV measurements, completed the Pittsburgh Sleep Quality Index (PSQI), and answered questions on exercise habits. Participants were grouped as short (< 6 h) or non-short sleepers (≥ 6 h), poor (> 5 PSQI global score), or good sleepers (< 6 PSQI global score), and exercise was divided into vigorous (VPA) and moderate (MPA) intensities. Based on CDC guidelines, VPA was classified into adequate (≥ 75 min/week) and inadequate (< 75 min/week) groups. For MPA, adequate (≥ 150 min/week) and inadequate (< 150 min/week) groups. Linear models, adjusted for sociodemographic and health-related covariates, examined the interaction between sleep duration/quality and exercise on HRV.

Results: Inadequate VPA was associated with lower HRV, HF-HRV (B = - 0.25, SE = 0.09, p = 0.007), and RMSSD (B = - 0.15, SE = 0.05, p = 0.0009). MPA showed no significant main associations with HRV. Sleep duration/quality did not show direct associations with HRV; however, interactions were found with sleep duration. Among short sleepers, inadequate VPA was associated with lower HF-HRV (B = - 0.62, SE = 0.25, p = 0.01) and inadequate MPA was associated with lower RMSSD (B = - 0.26, SE = 0.10, p = 0.01) compared to adequate exercise. Among non-short sleepers, there were no significant differences in HRV between exercise groups.

Conclusion: These findings suggest that short sleep and inadequate exercise may interact to lower HRV.