Perianal diseases, including hemorrhoids, anal fissures, and anal fistulas, affect millions of people and are often attributed to constipation, straining, sedentary behavior, pregnancy, or dietary habits. A new genetic epidemiology study now points to another potential contributor: disturbed sleep. Researchers from Peking University People’s Hospital report that insomnia, unusually long sleep duration, and daytime napping may increase the risk of hemorrhoidal disease, offering new evidence that sleep and anorectal health are connected through the body’s broader brain–gut and vascular systems.
The study, titled “The Interplay Between Sleep Patterns and Perianal Diseases: Sleep as a Risk Factor and Disease as a Consequence,” was conducted by Cuicui Pang, Yingshuo Wang, and Yanlin Wang and published in Neuropsychiatric Research. The investigators analyzed large-scale genome-wide association study data from individuals of European ancestry. Rather than relying solely on conventional observational associations, they used bidirectional two-sample Mendelian randomization, a method that uses naturally occurring genetic variants as instrumental variables to investigate whether a particular exposure is likely to have a causal effect on a disease outcome.
Mendelian randomization is based on the principle that genetic variants associated with a trait are allocated before disease develops and are generally less vulnerable to certain types of confounding than lifestyle measurements collected after the fact. In this analysis, genetic markers linked to sleep characteristics were examined in relation to perianal diseases, while a reverse analysis tested whether genetic susceptibility to perianal conditions could influence sleep traits. This two-way design allowed the researchers to explore whether poor sleep was more likely to precede hemorrhoidal disease or whether anorectal symptoms themselves were responsible for sleep disruption.
The strongest signal involved insomnia. Genetic predisposition to insomnia was associated with a 23.3 percent higher risk of hemorrhoidal disease, corresponding to an odds ratio of 1.2332 and a P value of 0.0002. The association remained statistically significant after correction for multiple testing, a process used to reduce the possibility that apparently positive results arise by chance when many traits and outcomes are examined simultaneously. Although the increase in individual risk may appear moderate, even modest effects can have substantial public health implications when the exposure is common across a population.
Two additional sleep traits were also associated with hemorrhoidal disease. Genetically predicted prolonged sleep duration was linked to a 16.2 percent increase in risk, with an odds ratio of 1.1618 and a P value of 0.0102. Daytime napping was associated with a 14.1 percent elevation in risk, corresponding to an odds ratio of 1.1413 and a P value of 0.0124. The findings do not establish that every person who sleeps for long periods or naps regularly will develop hemorrhoids. Instead, they suggest that genetic liability to these sleep patterns overlaps with biological pathways that may make hemorrhoidal disease more likely.
The biological explanation proposed by the researchers centers on the close relationship between circadian regulation, intestinal function, inflammation, and venous circulation. Sleep–wake rhythms influence the autonomic nervous system, hormone production, immune activity, and gastrointestinal motility. When circadian timing is disrupted, intestinal movement may become less regular, increasing the likelihood of constipation or difficult bowel movements. Repeated straining and prolonged time on the toilet can raise pressure within the hemorrhoidal venous plexus, the network of blood vessels that supports the anal canal, potentially contributing to vascular enlargement and symptomatic hemorrhoids.
Insufficient or fragmented sleep may also promote a persistent low-grade inflammatory state. Sleep loss has been associated with changes in inflammatory mediators, stress hormones, endothelial function, and metabolic regulation. In the anorectal region, these changes could theoretically worsen vascular congestion, tissue swelling, and sensitivity to mechanical stress. At the same time, people who nap frequently or spend extended periods asleep may engage in less physical activity during the day. Reduced movement can impair venous return from the pelvis and lower limbs, while sedentary behavior may further contribute to constipation and prolonged sitting—two established contributors to hemorrhoidal symptoms.
The reverse Mendelian randomization analysis found no significant evidence that perianal diseases causally alter the studied sleep traits. This result supports the possibility that sleep disturbances act primarily as an upstream risk factor rather than merely reflecting discomfort caused by hemorrhoids or other anorectal disorders. However, the absence of a reverse association should not be interpreted as proof that perianal pain never affects sleep. Patients with severe inflammation, bleeding, fissures, or fistulas can certainly experience nighttime discomfort. The genetic analysis addresses population-level causal tendencies and does not eliminate the complex, individual feedback loops that can occur between pain, anxiety, sleep loss, and gastrointestinal symptoms.
The findings could eventually influence the clinical management of hemorrhoidal disease by encouraging physicians to ask about sleep quality alongside bowel habits, diet, physical activity, and toileting behavior. Improving sleep might support anorectal health indirectly by promoting more stable circadian rhythms, better gastrointestinal motility, and healthier activity patterns. Cognitive behavioral therapy for insomnia, regular sleep and wake times, reduced exposure to stimulating light before bedtime, and a sleep environment that supports uninterrupted rest may be useful components of a broader lifestyle strategy. Adequate dietary fiber, hydration, and physical activity remain central measures for preventing constipation and should not be replaced by sleep interventions.
The researchers acknowledge important limitations. The study relied on genetic data from European-ancestry populations, so the results may not apply equally to people from other ethnic and geographic backgrounds. Some genetic instruments were selected using a less stringent threshold, which can increase the risk that weak or imperfectly specific variants influence the estimates. Mendelian randomization also depends on assumptions: the genetic variants must be strongly associated with the exposure, must not be linked to major confounding factors, and should affect the disease primarily through the exposure being studied. Additional research using diverse populations, clinical sleep assessments, longitudinal patient data, and biological measurements will be needed to clarify the mechanisms. Even with these caveats, the study adds a significant piece to the emerging picture of perianal disease as a condition shaped not only by local mechanical forces, but also by systemic rhythms connecting the brain, gut, immune system, and circulation.
Article Title: The Interplay Between Sleep Patterns and Perianal Diseases: Sleep as a Risk Factor and Disease as a Consequence
Web References: https://doi.org/10.2738/NPR.2026.0006
Keywords: sleep, insomnia, hemorrhoidal disease, perianal diseases, Mendelian randomization, circadian rhythm, constipation, inflammation, brain–gut axis, anorectal health
