Objective Sleepiness Without Daytime Fatigue Linked to Lower Hypertension Risk

Individuals who fall asleep quickly during overnight sleep testing, but do not report feeling excessively sleepy during the day, may actually be at lower risk for both existing and future hypertension, according to a new study published in Sleep.¹ The results, drawn from one of the largest community-based sleep studies to date, challenge long-held assumptions about the relationship between sleepiness and cardiovascular health.

As many as 33% of adults in the general population report excessive daytime sleepiness, a condition associated with depression, obesity, diabetes, and hallmark sleep disorders, including sleep apnea.²

The study evaluated 1590 adults without a complaint of excessive daytime sleepiness and used overnight polysomnography to assess sleep onset latency (SOL), a measure of how quickly a person falls asleep.¹ Short SOL, defined as 7 minutes or less, served as an indicator of objective sleepiness. Roughly 10% of participants met this criterion. Hypertension prevalence across the cohort was 34.3%.

At baseline, the prevalence of hypertension differed substantially across SOL groups. Individuals with objective sleepiness had the lowest hypertension prevalence of 22.1% compared with 32.3% in the control group and 39.6% among those with long sleep latency. After adjusting for a wide range of confounders, including demographic, clinical, and sleep characteristics, objective sleepiness remained associated with a significantly reduced likelihood of prevalent hypertension. Participants in the short-SOL group were 14.9% less likely to have hypertension than controls (OR, 0.44; 95% CI, 0.23-0.81; P = .010). By contrast, long SOL was not associated with reduced or increased hypertension risk.

When researchers analyzed SOL as a continuous variable, they observed a significant nonlinear association between sleep latency and hypertension risk, reinforcing the finding that very short latencies carry unique physiological implications. In addition, individuals with objective sleepiness had the highest prevalence of normal blood pressure and the lowest prevalence of uncontrolled hypertension.

The protective pattern extended into the longitudinal arm of the study. Among 659 adults without hypertension at baseline, followed for an average of 7.5 years, 18% developed hypertension. Incident hypertension was significantly lower among those with objective sleepiness (8.8%) compared with both the control group (17.3%) and participants with long SOL (19.1%), with strong statistical significance for both comparisons. Objective sleepiness corresponded to an 11.2% absolute risk reduction in incident hypertension, and adjusted models confirmed the association (OR, 0.31; 95% CI, 0.10-0.90; P = .031). Importantly, this protective effect held even after accounting for baseline blood pressure levels.

As in the cross-sectional analysis, long SOL did not meaningfully alter the risk of developing hypertension over time. Analyses treating SOL as a continuous variable also revealed a significant nonlinear relationship with incident hypertension risk.

However, the protective association was not universal. When researchers looked at participants with subjective excessive daytime sleepiness, alone or combined with objective sleepiness, the benefit disappeared. The combination of subjective and objective sleepiness was associated with an increased risk of hypertension, although the estimates were not statistically significant due to a small sample size. This pattern held in both cross-sectional and longitudinal analyses.

The findings introduce a surprising nuance to the understanding of sleepiness and cardiovascular risk. Traditionally, excessive daytime sleepiness has been linked to adverse cardiometabolic outcomes, but this study suggests that objective sleepiness in the absence of daytime symptoms may reflect different physiological processes—potentially a more efficient sleep regulatory system or an adaptive response that mitigates hypertension risk.

The authors emphasize that these results have practical implications for clinicians. Incorporating objective sleepiness metrics from polysomnography may offer additional insight into a patient’s cardiovascular profile, particularly when subjective symptoms are absent. Further research is needed to determine the mechanisms underlying this unexpected protective relationship, but the study adds a new dimension to the evolving connection between sleep health and cardiovascular outcomes.

References

1. Athanasiou N, Pejovic S, Fernandez-Mendoza J, et al. Objective sleepiness without a subjective complaint decreases hypertension risk. Sleep. 2025;zsaf394. doi:10.1093/sleep/zsaf394

2. Bixler EO, Vgontzas AN, Lin HM, Calhoun SL, Vela-Bueno A, Kales A. Excessive Daytime Sleepiness in a General Population Sample: The Role of Sleep Apnea, Age, Obesity, Diabetes, and Depression. J Clin Endocrinol Metab. 2005;90(8):4510-4515. doi:10.1210/jc.2005-0035