The research team, led by investigators at the University of Texas Health Science Center at Houston, analyzed self-reported data from 11,039 adults aged 18 to 65 years. The sample had a mean age of 41 years, was slightly majority female at 50.7 percent, and reflected the country’s diversity: 59.8 percent of participants were non-Hispanic White, 17.8 percent Hispanic or Latino, 12 percent non-Hispanic Black, and 6.3 percent non-Hispanic Asian. Participants reported whether they engaged in moderate or vigorous physical activity at work, defined as tasks such as carrying light loads, household chores, and yard work, or in recreational settings, such as running, swimming, and team sports. Moderate activity was described as movement causing a small increase in breathing or heart rate sustained for at least ten minutes, while vigorous activity caused large increases over the same duration.

Sleep behaviors were captured through a battery of NHANES questions covering five domains: usual sleep duration on weekdays or workdays, frequency of snoring over the past year, episodes of snorting, gasping, or breathing cessation during sleep, whether a doctor had ever been told about trouble sleeping, and how often the participant felt excessively sleepy during the day in the past month. Short sleep duration was defined as fewer than seven hours per night, in line with recommendations from the American Academy of Sleep Medicine and the Sleep Research Society that adults obtain at least seven hours of nightly sleep. The researchers then applied weighted logistic regression models, adjusting for age, sex, ethnicity, body mass index categories, and socio-economic status proxied by the family income to poverty ratio.

The headline finding is striking. Moderate work activity increased the odds of short sleep duration by 42 percent, snoring by 45 percent, breath cessation during sleep by 37 percent, and daytime sleepiness by 63 percent. Vigorous work activity was even more strongly linked to short sleep, raising its odds by 72 percent, alongside a 42 percent increase in the odds of snoring, a 31 percent increase in breath cessation, and a 21 percent increase in daytime sleepiness. In contrast, vigorous recreational activity moved in the opposite direction, reducing the odds of short sleep duration by 19 percent and the odds of trouble sleeping by 17 percent. Moderate recreational activity showed no significant associations with sleep behaviors after adjustment, suggesting that the protective effect of leisure movement may require a sufficiently vigorous intensity.

The burden of poor sleep associated with work-related exertion was not distributed evenly across the population. In stratified analyses, non-Hispanic Black participants engaging in moderate work activity showed consistently elevated odds of all measured sleep behaviors, with the highest odds observed for daytime sleepiness. Hispanic participants engaging in moderate work activity had the highest odds of snoring within that group, while among those performing vigorous work activity, Hispanic participants showed the greatest odds of short sleep duration and non-Hispanic Asian participants the greatest odds of snoring and of trouble sleeping. These ethnicity-specific patterns emerged even though a formal interaction analysis found no statistically significant effect modification, indicating that the direction of associations was broadly similar but the magnitude differed meaningfully across groups.

The authors propose several mechanisms that could explain why work-related activity appears to harm sleep while recreational activity appears to protect it. Occupational physical exertion often coincides with long hours, shift schedules including overnight work, and physically demanding conditions that disrupt circadian rhythms and promote fatigue and exhaustion. Prior research has estimated that moderate-to-vigorous work activity is associated with roughly a 15 percent increase in the likelihood of disordered sleep. Stress is another candidate driver: elevated cortisol levels, mediated through the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, are well-established predictors of poor sleep quality and insomnia, and occupational pressures, financial instability, and socio-economic disadvantage can sustain chronic stress responses that fragment sleep.

By contrast, the benefits of leisure-time exercise are extensively documented. Regular moderate-to-vigorous recreational activity promotes cardiovascular health, favorable genetic biomarker profiles, and musculoskeletal fitness, which in turn support glucose homeostasis, bone health, psychological well-being, and overall quality of life. Recreational exercise has also been shown in previous studies to protect against the development of sleep disorders, a finding consistent with the reduced odds of short sleep and trouble sleeping observed here. The distinction between the two contexts of movement may therefore reflect not the physiology of exercise itself but everything that surrounds it: autonomy, scheduling, stress, and recovery time.

Metabolic health added another layer of complexity. Participants with obesity, who made up 40.2 percent of the sample, showed increased odds of short sleep duration, snoring, and breath cessation, consistent with the established link between adiposity and obstructive sleep apnea, in which fat deposited around the neck contributes to airway obstruction during sleep. Hormonal disruptions associated with obesity, including elevated evening cortisol and ghrelin and reduced leptin, are known to be bidirectionally related to sleep loss. Intriguingly, underweight participants engaging in moderate recreational activity had more than three times the odds of experiencing breath cessation compared with those who did not, a finding the authors suggest may relate to reduced lung capacity and weaker respiratory muscles in underweight individuals, though they caution that further longitudinal research is needed to confirm this mechanism.

The study’s strengths include its large, nationally representative sample, the use of NHANES’s complex weighting methodology to account for the clustered, stratified sampling design, and its unprecedented attention to the type and intensity of physical activity alongside ethnicity and body weight. Still, the authors are careful to note the limitations inherent in the design. The cross-sectional data cannot establish temporality or causation, and both sleep behaviors and physical activity were self-reported rather than confirmed by polysomnography or measured objectively with accelerometers. The analysis also could not account for potential confounders such as occupation type, workplace conditions, marital status, stress, and environmental factors. The authors call for prospective longitudinal studies to clarify the mechanisms linking different forms of physical activity to sleep health and to examine the social and workplace factors that may drive the disparities observed across ethnic and weight groups.

For the public, the message is nuanced rather than simple. Moving more remains one of the most reliable routes to better health, and only about half of American adults currently meet federal guidelines of 150 to 300 minutes of moderate or 75 to 150 minutes of vigorous aerobic activity per week. But this research suggests that the clock and the context of that movement matter: exertion embedded in demanding, potentially stressful work was associated with shorter, more disturbed sleep, while vigorous exercise chosen freely in leisure time was associated with longer and sounder rest. As sleep scientists push to elevate sleep health on public health agendas, the findings underscore that interventions to improve sleep may need to look beyond exercise volume and address the conditions under which people are physically active, particularly for the ethnic and weight groups that bear the heaviest burden of poor sleep.

Subject of Research: Associations between work-related and recreational physical activity and sleep behaviors in US adults

Article Title: Unraveling the relationship between sleep behaviors and physical activity in the United States: insights from 2015 to 2020 NHANES data

Article References: Ernest, D. K., Singh, B., Shamna, F., Onugha, E. A., & Sharma, S. V. (2024). Unraveling the relationship between sleep behaviors and physical activity in the United States: insights from 2015 to 2020 NHANES data. Journal of Activity, Sedentary and Sleep Behaviors, 3(1), Article 31. https://doi.org/10.1186/s44167-024-00070-8

Image Credits: AI Generated

DOI: 10.1186/s44167-024-00070-8

Keywords: sleep health, physical activity, NHANES, work activity, recreational exercise, sleep duration, sleep apnea, ethnic disparities, obesity, daytime sleepiness, cross-sectional study, public health