Does insomnia predict a high risk of cancer? A systematic review and meta-analysis of cohort studies.

Recently, emerging studies on the relationship between insomnia, the most common sleep disorder, and cancer have been published, but with inconsistent results. With the development of society and the accelerated pace of life, more and more people experience insomnia. Therefore, it is important to clarify the association. Relevant literature was obtained through a search of seven databases and supplementary searches. After a strict screening, eight cohort studies (seven prospective and one retrospective) involving 578,809 participants and 7,451 cancer events were incorporated into our analysis. The results demonstrate a modest 24% overall increased risk of cancer for individuals with insomnia in comparison to those without insomnia. The sensitivity analysis shows that the correlation between the two is stable. Subgroup analyses show that the risk of developing cancer was significantly higher in studies conducted in women (HR = 1.24; 95% CI, 1.01-1.53), but not in men (HR = 1.28; 95% CI, 0.90-1.80). Similarly, in terms of specific cancer types, the pooled HR was only significantly higher in thyroid cancer (HR = 1.36; 95% CI, 1.12-1.65) and not in other types of cancer (p > 0.05). Our findings suggest that insomnia may serve as an early warning sign of the onset of cancer and provide an opportunity for early detection and early intervention. Our findings should be treated with caution because of the limited number of included studies and potential bias. More additional studies are warranted to provide more information on the carcinogenic effect of insomnia.