Sleep and cancer: Synthesis of experimental data and meta-analyses of cancer incidence among some 1,500,000 study individuals in 13 countries

Abstract

Sleep and its impact on physiology and pathophysiology are researched at an accelerating pace and from many different angles. Experiments provide evidence for chronobiologically plausible links between chronodisruption and sleep and circadian rhythm disruption (SCRD), on the one hand, and the development of cancer, on the other. Epidemiological evidence from cancer incidence among some 1 500 000 study individuals in 13 countries regarding associations with sleep duration, napping or "poor sleep" is variable and inconclusive. Combined adjusted relative risks (meta-RRs) for female breast cancer, based on heterogeneous data, were 1.01 (95% CI: 0.97-1.06). Meta-RRs for cancers of the colorectum and of the lung in women and men and for prostate cancer were 1.08 (95% CI: 1.03-1.13), 1.11 (95% CI: 1.00-1.22) and 1.05 (95% CI: 0.83-1.33), respectively. The significantly increased meta-RRs for colorectal cancer, based on homogeneous data, warrant targeted study. However, the paramount epidemiological problem inhibiting valid conclusions about the associations between sleep and cancer is the probable misclassification of the exposures to facets of sleep over time. Regarding the inevitable conclusion that more research is needed to answer How are sleep and cancer linked in humans? we offer eight sets of recommendations for future studies which must take note of the complexity of multidirectional relationships.

Relationship between subjective and actigraphy-measured sleep in 237 patients with metastatic colorectal cancer

“…[12–15] Moreover, poor, short sleep and daytime naps have been shown to be associated with an increased risk for the development of colorectal cancer in a recent meta-analysis involving about 1.5 million individuals worldwide. [16] Approximately half of colorectal cancer patients report sleep disruption. [17] Similar figures have been described for circadian disruption in this clinical setting.…”

Sleep, mortality and beyond: A magician can't pull more from the hat than has been put in earlier

“…Finally, our complements to the study by Liu et al follow meta-analyses into sleep and incident cancer [8). Our impression was that methodology outstripped the capacity of 'usual sleep study data' and this appears the case with regard to the work by Liu et al as well.…”

“…In theory, impaired sleep could be a consequence and/or cause of incident cancer [8]. In practice, Cairns et al suggested complex napping-associated effects after examining information over time: Short-term increases in risk associated with daytime napping, the authors concluded, probably reflected pre-clinical disease and did not evince that napping caused -or contributed to -observed cancer cases [10].…”

“…As a feasible step ahead, researchers may want to focus more on the timing of sleep as this may determine the quality and quantity of sleep as well [8,9]. To this end, accumulated sleep disruptions -operationalized by how much individuals sleep during their biological day rather than night -could be tested as another alternative measure in sleep research [9].…”

Environmental noise and breast cancer risk?

“…Thus, a recent meta-analysis based on seven studies estimated a relative risk of breast cancer close to unity (15), and same tendency is seen for hormone-related cancers, including breast cancer and cancer in general in another meta-analysis (16). Also the most recent meta-analysis by Erren et al (17) confirms no association between "poor sleep" and breast cancer risk (17). Finally, no association between sleep duration and breast cancer prognosis has been found among breast cancer survivors (18).…”