Poor Sleep, Not Shift Schedules, Drives Belly Fat in Hospital Workers, Study Finds

A new study of nurses and paramedical healthcare workers at a large public hospital in Karachi, Pakistan, has found that more than half of the staff surveyed carried excess fat around their abdomen, and that the strongest predictors were not the famously punishing rotating shift schedules but something more subtle: poor sleep quality, older age, and years spent on the job. The research, published in BMC Public Health, offers a nuanced picture of how the biology of disrupted rest interacts with occupational life in a workforce often assumed to be protected by its medical knowledge.

The investigation was designed as an analytical cross-sectional study, meaning the researchers measured exposures and outcomes at a single point in time rather than following participants forward through the years. Between December 2024 and May 2025, the team, led by researchers at the School of Public Health and the Dow Institute of Nursing and Midwifery at Dow University of Health Sciences, recruited 279 nurses and paramedical workers aged 25 to 55. Participants were enrolled through non-probability consecutive sampling, a practical approach in which every eligible person who presents during the recruitment window is invited to take part until the target number is reached. While efficient, this method means the sample may not perfectly represent the entire hospital workforce, a limitation the authors implicitly acknowledge through their careful statistical adjustment.

Abdominal obesity, the outcome of primary interest, is not simply a matter of a tight waistband. Fat deposited around the internal organs, so-called visceral fat, is metabolically active tissue that secretes inflammatory signaling molecules, interferes with insulin signaling, and is strongly linked to type 2 diabetes, cardiovascular disease, and components of the metabolic syndrome. Measuring it, typically through waist circumference thresholds, gives clinicians a window into risk that body mass index alone can miss, particularly in populations whose body composition differs from the reference groups on which standard charts were built.

To assess sleep, the researchers used the Pittsburgh Sleep Quality Index, or PSQI, one of the most widely validated instruments in sleep research. The PSQI does not merely ask how long someone sleeps; it probes seven domains, including subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. A composite score above established cutoffs classifies a respondent as a poor sleeper. For shift workers, whose rest is frequently fragmented by night duties and irregular rosters, this multidimensional capture matters, because a person can technically log adequate hours yet still sleep badly.

The headline finding was stark: 150 of the 279 participants, or 53.8 percent, met the criteria for abdominal obesity. In the first round of analysis, a univariable examination that looks at each factor in isolation, abdominal obesity was significantly associated with being older than 30, being female, having more than five years of work experience, marital status, having children, poor sleep quality, and a fixed rather than rotating duty schedule. That last association, in which fixed schedules appeared riskier than rotation, raised an intriguing question: was the shift rotation itself really the culprit, or was it standing in for something else?

To untangle this web, the team turned to multivariable logistic regression, a statistical technique that estimates the independent effect of each factor while holding the others constant. The method yields adjusted odds ratios, or aORs, which express how many times more likely an outcome is in one group compared with a reference group, along with 95 percent confidence intervals that indicate the precision of the estimate. When an interval crosses 1.0, the association is not statistically distinguishable from no effect at the conventional threshold, and the researchers treated p-values of 0.05 or below as significant.

After adjustment, the picture sharpened considerably. Workers older than 30 had nearly five times the odds of abdominal obesity compared with younger colleagues, with an adjusted odds ratio of 4.83 and a confidence interval running from 2.06 to 11.33. Those with more than five years of professional experience had 2.68 times the odds, with a confidence interval of 1.23 to 5.83. Poor sleep quality nearly quadrupled the odds, at 3.82 with an interval of 1.86 to 7.84. Meanwhile, male gender was associated with substantially lower odds than female gender, at an adjusted odds ratio of 0.31, meaning men in this sample were roughly a third as likely to carry abdominal fat as their female counterparts after accounting for other variables.

Perhaps the most consequential negative finding concerned duty schedule itself. Once the model accounted for age, experience, sleep quality, and the other covariates, neither rotating shifts nor fixed schedules showed a statistically significant association with abdominal obesity. The same held true for the number of children, family income, hospital department, professional category, and marital status. In other words, the crude association seen with fixed schedules in the univariable analysis appears to have been a statistical echo of other factors rather than an independent occupational effect. This matters because shift rotation has long been cast as a primary villain in the metabolic health of healthcare workers, and this study suggests the pathway may run less through the roster and more through the sleep it disturbs.

The biological plausibility of the sleep-obesity link is well developed in the broader literature. Short or fragmented sleep alters the pulsatile secretion of growth hormone, blunts insulin sensitivity within days, and dysregulates the appetite hormones leptin and ghrelin in ways that bias people toward calorie-dense food. Chronic sleep restriction also elevates evening cortisol, promoting fat deposition in visceral depots. For hospital staff, these mechanisms are compounded by the practical realities of night work: canteen options at 3 a.m., limited time for exercise, and stress hormones kept on a low simmer by demanding clinical duties. The Karachi study cannot prove causation, since a cross-sectional design captures a snapshot rather than a trajectory, and reverse causality remains possible, with abdominal obesity itself worsening sleep through conditions such as obstructive sleep apnea.

Still, the implications are actionable. The authors conclude that abdominal obesity is highly prevalent among the healthcare workers studied and that poor sleep quality stands out as a modifiable risk factor, unlike age or accumulated years of service. Hospitals designing occupational health programs might reasonably prioritize sleep hygiene education, screening for sleep disorders, and scheduling practices that protect sleep continuity, even if the rotation pattern itself is not the direct driver. The study received no external funding, was approved by the institutional review board of Dow University of Health Sciences, and was conducted with written informed consent under the Declaration of Helsinki. As healthcare systems worldwide grapple with workforce burnout and chronic disease among their own staff, this Karachi-based analysis adds a data point with global resonance: the battle against the bulge in scrubs may be won or lost in the quality of the hours between shifts, not merely in their arrangement on the roster.

Subject of Research: Association of rotating shift work and sleep quality with abdominal obesity among nurses and paramedical healthcare workers

Article Title: Exploring association of rotating shift work and sleep quality with abdominal obesity among nurses and paramedical healthcare workers: an analytical cross-sectional study

Article References: Urf Maryam, M. J., Rasheed, A., Adil, S. O., Ansari, A. A., Mangi, S. J. A., & Singh, J. (2026). Exploring association of rotating shift work and sleep quality with abdominal obesity among nurses and paramedical healthcare workers: an analytical cross-sectional study. BMC Public Health. https://doi.org/10.1186/s12889-026-29619-9

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29619-9

Keywords: shift work, sleep quality, abdominal obesity, healthcare workers, occupational health, Pittsburgh Sleep Quality Index, nurses, logistic regression, metabolic syndrome, Pakistan, public health, cross-sectional study