The association between sleep quantity, insomnia and lung cancer risk - A systematic review and meta-analysis

PURPOSE

The effect of various sleep traits on the risk of lung cancer differs among pre-existing studies. This study aims to systematically review and synthesise the association between sleep duration and insomnia with the incidence of lung cancer.

METHODS

PubMed, Embase and The Cochrane Library were searched from inception to 23 April 2023 for observational studies examining the effect of sleep quantity or insomnia on lung cancer incidence. We pooled maximally-adjusted hazard ratios and odds ratios separately using random effects inverse variance weighted models. The risk of bias of observational studies was assessed using the Newcastle-Ottawa Scale.

RESULTS

We included 11 observational studies with a pooled cohort of 5,049,141 patients. The mean age of the patients was 49.5 ± 17.7 years, and 51.4% were males. The risk of bias ranged from low-moderate. Individuals who slept for a shorter or longer duration than the reference range of sleep per night showed an increased risk of lung cancer by 11% (HR:1.11; 95%CI:1.00-1.23) and 16% (HR:1.16; 95%CI:1.06-1.27) respectively. Furthermore, individuals with insomnia symptoms had a 9% greater risk of lung cancer than those without symptoms (HR:1.09; 95%CI:1.05-1.13).

CONCLUSION

This study suggests that insufficient sleep, excessive sleep and insomnia may be associated with an increased risk of lung cancer. Physicians should be mindful of this association and encourage healthy sleep practises among patients. Given the observed heterogeneity among some pre-existing studies, future research with longer periods of follow-up, greater control for covariates and objective testing of sleep parameters may add value to this topic.

Sleep disturbances and the risk of lung cancer: a meta-epidemiological study

BACKGROUND

The relationship between sleep disturbances and lung cancer is complex and bidirectional. This meta-epidemiological study aimed to explore the potential association between sleep disruption and the risk of pulmonary cancer.

METHODS

We conducted a comprehensive literature search of the PubMed, Embase, Cochrane Library, and Web of Science databases to retrieve relevant studies. We employed the Newcastle-Ottawa Scale to assess the quality of the observational studies. Stata 17.0 was used to synthesize and conduct a meta-analysis of odds ratios (ORs) and corresponding 95% confidence intervals (CIs). We used funnel plot analysis and Egger's regression test to evaluate potential publication bias.

RESULTS

A total of 11 studies were included with 469,691 participants. The methodological quality of the included studies ranged from moderate to high. Compared with 7-8 h of sleep time, short sleep duration was associated with a 13% higher lung cancer risk [OR, 1.13; 95%CI: 1.02-1.25; I2 = 67.6%; P = 0.018] and long sleep duration with a 22% higher risk [OR, 1.22; 95%CI: 1.12-1.33; I2 = 6.9%; P < 0.001]. Insomnia symptoms [OR, 1.11; 95%CI: 1.07-1.16; I2 = 0%; P < 0.001] and evening chronotype [OR, 1.15; 95%CI: 1.05-1.26; P = 0.002] were all related to a higher risk of lung cancer. Egger's test revealed no publication bias for sleep duration (P = 0.13).

DISCUSSION

This systematic review is the first one which observes positive correction between sleep disturbances and the incidence of lung cancer. While the plausible mechanism is not clear, it is hypothesized that the association of short sleep duration and lung cancer mainly mediated by melatonin secretion and the immune-inflammatory balance. Further studies are needed to examine whether other risk factors, such as age, occupation, cumulative effect of sleep disturbances might mediate the relationship between sleep disturbances and lung cancer risk.

CONCLUSION

The present study revealed that insufficient and excessive sleep duration, insomnia symptoms, and evening chronotype were significantly predictive of an increased risk of lung cancer. This finding underscores the need to account for sleep disturbances as an independent risk factor for evaluating susceptibility to lung cancer.

TRIAL REGISTRATION

CRD42023405351.

Sleep Traits, Night Shift Work and Lung Cancer Risk among Women: Results from a Population-Based Case-Control Study in France (The WELCA Study)

Circadian rhythm disruption due to night shift work and/or sleep disorders is associated with negative health outcomes including cancer. There is only scant evidence of an association with lung cancer, unlike breast and prostate cancer. We explore the role of sleep disorders and night shift work in lung cancer risk among women in a population-based case-control study, including 716 lung cancer cases and 758 controls. Multivariable logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) associated with sleep duration per day (<7 h, 7−7.9 h, ≥8 h), a summary index of sleep disorders, chronotype, and night shift work exposure metrics. When compared to women with an average sleep duration of 7−7.9 h per day, the OR was 1.39 (95% CI 1.04−1.86) in long sleepers (≥8 h) and 1.16 (95% CI 0.86−1.56) in short sleepers (<7 h). Overall, lung cancer was not associated with the sleep disorder index, nor with night shift work, regardless of the duration of night work or the frequency of night shifts. However, elevated OR associated with the sleep disorder index were found in the subgroup of current smokers. The U-shaped association of lung cancer with sleep duration was more particularly pronounced among women who worked at night ≥5 years. Our findings suggested that sleep patterns are associated with lung cancer risk in women with a potential modifying effect by night shift work duration or tobacco smoking.

Association of sleep duration at age 50, 60, and 70 years with risk of multimorbidity in the UK: 25-year follow-up of the Whitehall II cohort study

BACKGROUND

Sleep duration has been shown to be associated with individual chronic diseases but its association with multimorbidity, common in older adults, remains poorly understood. We examined whether sleep duration is associated with incidence of a first chronic disease, subsequent multimorbidity and mortality using data spanning 25 years.

METHODS AND FINDINGS

Data were drawn from the prospective Whitehall II cohort study, established in 1985 on 10,308 persons employed in the London offices of the British civil service. Self-reported sleep duration was measured 6 times between 1985 and 2016, and data on sleep duration was extracted at age 50 (mean age (standard deviation) = 50.6 (2.6)), 60 (60.3 (2.2)), and 70 (69.2 (1.9)). Incidence of multimorbidity was defined as having 2 or more of 13 chronic diseases, follow-up up to March 2019. Cox regression, separate analyses at each age, was used to examine associations of sleep duration at age 50, 60, and 70 with incident multimorbidity. Multistate models were used to examine the association of sleep duration at age 50 with onset of a first chronic disease, progression to incident multimorbidity, and death. Analyses were adjusted for sociodemographic, behavioral, and health-related factors. A total of 7,864 (32.5% women) participants free of multimorbidity had data on sleep duration at age 50; 544 (6.9%) reported sleeping ≤5 hours, 2,562 (32.6%) 6 hours, 3,589 (45.6%) 7 hours, 1,092 (13.9%) 8 hours, and 77 (1.0%) ≥9 hours. Compared to 7-hour sleep, sleep duration ≤5 hours was associated with higher multimorbidity risk (hazard ratio: 1.30, 95% confidence interval = 1.12 to 1.50; p < 0.001). This was also the case for short sleep duration at age 60 (1.32, 1.13 to 1.55; p < 0.001) and 70 (1.40, 1.16 to 1.68; p < 0.001). Sleep duration ≥9 hours at age 60 (1.54, 1.15 to 2.06; p = 0.003) and 70 (1.51, 1.10 to 2.08; p = 0.01) but not 50 (1.39, 0.98 to 1.96; p = 0.07) was associated with incident multimorbidity. Among 7,217 participants free of chronic disease at age 50 (mean follow-up = 25.2 years), 4,446 developed a first chronic disease, 2,297 progressed to multimorbidity, and 787 subsequently died. Compared to 7-hour sleep, sleeping ≤5 hours at age 50 was associated with an increased risk of a first chronic disease (1.20, 1.06 to 1.35; p = 0.003) and, among those who developed a first disease, with subsequent multimorbidity (1.21, 1.03 to 1.42; p = 0.02). Sleep duration ≥9 hours was not associated with these transitions. No association was found between sleep duration and mortality among those with existing chronic diseases. The study limitations include the small number of cases in the long sleep category, not allowing conclusions to be drawn for this category, the self-reported nature of sleep data, the potential for reverse causality that could arise from undiagnosed conditions at sleep measures, and the small proportion of non-white participants, limiting generalization of findings.

CONCLUSIONS

In this study, we observed short sleep duration to be associated with risk of chronic disease and subsequent multimorbidity but not with progression to death. There was no robust evidence of an increased risk of chronic disease among those with long sleep duration at age 50. Our findings suggest an association between short sleep duration and multimorbidity.

Association of delayed chronotype with allergic diseases in primary school children

To investigate the associations of sleep midpoint for both weekdays and weekends, and chronotype, with allergic diseases, specifically asthma, allergic rhinitis, and eczema in primary school children. In this cross-sectional study, we evaluated 10409 children between 7 and 12 years of age (mean 9.21 ± 1.51 years; male 52.2%). Each allergic disease was defined as children with both diagnosed disease and current symptoms, and the reference group was described as children without any allergic symptoms. Sleep durations and mid-sleep times were calculated by reported sleep timing. Chronotype was determined by mid-sleep time on free days corrected for oversleeping. Children with allergies have shorter sleep duration and later sleep preferences. Late weekly sleep midpoints were associated with higher odds of allergies, and the odds were even higher for later weekday midpoints than their weekend counterparts. Regarding chronotype, the more evening chronotype, the higher the odds of allergic rhinitis and eczema. Additionally, effect of weekday late sleep midpoint on allergies was stronger as the participants who slept less (asthma: aOR,1.62, 95 CI%,1.25-2.10, p < .001; allergic rhinitis: aOR,2.12, 95 CI%,1.68-2.67, p < .001; eczema: aOR, 1.94, 95 CI%,1.52-2.48, p < .001). Further, the associations of chronotype with allergic rhinitis were confounded by second-hand smoking exposure. Our study, which finds an association between chronotype and the odds of three allergic diseases, hopes to improve sleep health awareness, especially in the particular population with allergic diseases, and describes the importance of evaluating modifiable behavioral factors, such as sleep habits, as a plausible factor for the prevention and treatment of allergic diseases.

Night work, chronotype and risk of endometrial cancer in the Screenwide case-control study

BACKGROUND

Circadian disruption caused by night work has been associated with hormonal-related cancers such as breast and prostate cancer. Data on the role of circadian factors in the aetiology of endometrial cancer, an oestrogen-associated cancer, are scarce.

METHODS

We examined the association between endometrial cancer and night shift work, chronotype (a characteristic correlating with preference for morning or evening activity) and sleep duration, in 180 incident cases and 218 hospital controls. Participants were interviewed face-to-face by trained interviewers to collect information on sociodemographic factors, familial, medical, occupational history (including work shifts), sleep duration and chronotype, and other lifestyle factors. We used logistic regression models adjusted for potential confounders to estimate ORs and 95% CIs.

RESULTS

After adjustment by potential confounders, we found an inverse not statistically significant association between ever worked in night shifts and endometrial cancer (OR=0.64; 95% CI=0.35 to 1.16). Associations were irrespective of shift type (permanent or rotating nights) or duration of night work. We did not observe any statistically significant association between endometrial cancer and sleep duration, while inconsistent patterns were observed for chronotype and endometrial cancer risk.

CONCLUSIONS

These data do not support a role for circadian disruption in the carcinogenesis of endometrial cancer.

Sleep duration, chronotype, and insomnia and the risk of lung cancer: United Kingdom Biobank Cohort

BACKGROUND

Relationships between sleep duration, chronotype, insomnia and lung cancer risk have not been comprehensively examined. Inter-relations between sleep traits on the risk of lung cancer have not been assessed. We aimed to examine sleep traits with lung cancer risk.

METHODS

Participants were recruited between 2006 - 2010 and followed through November 30th, 2020. We included 382,966 participants (3,664 incident lung cancer) in analysis. Cox proportional hazards models estimated hazards ratios (HR) and 95% confidence intervals (CI) for associations between sleep duration, chronotype, and insomnia symptoms and lung cancer risk. Joint effects analyses were examined between sleep duration and three traits (chronotype,insomnia,daytime napping). Non-linear associations between sleep duration and lung cancer risk were assessed in restricted cubic spline analysis.

RESULTS

Longer sleep (>8 hours) was positively associated with lung cancer risk compared with normal sleep duration (7-8 hours; HR=1.22; 95% CI: 1.10, 1.36). Frequent insomnia symptoms increased the risk of lung cancer compared with never/rarely experiencing symptoms (HR= 1.16; 95% CI: 1.05, 1.28). Joint effects between sleep duration and chronotype, and sleep duration and insomnia symptoms were observed. In analysis excluding participants reporting shift work at baseline, evening chronotypes ('slight', 'definite') were at a greater risk of lung cancer compared with definite morning chronotype (HR=1.17; 95% CI: 1.06, 1.28 and HR=1.37; 95% CI: 1.21, 1.54, respectively).

CONCLUSIONS

Sleep traits such as long sleep duration, frequent insomnia symptoms, and definite evening chronotype may be risk factors for lung cancer. Joint effects should be further investigated.

IMPACT

Sleep traits may be risk factors of lung cancer.

Both increased and decreased sleep duration over time are associated with subsequent cancer development

PURPOSE

Changes in sleep duration have been reported to correlate with lifestyle-related diseases in humans. However, equivalent studies regarding the effects of sleep on cancer progression are lacking. This study aimed to determine whether or not increase or decrease in sleep duration over time is associated with subsequent cancer development.

METHODS

A large-scale, retrospective cohort study was conducted at a preventive medicine health center at a general community hospital in Tokyo, Japan. All participants who underwent health checkups at the hospital between January 2005 and December 2018 were included. The primary study outcome was development of any type of cancer according to the slope of sleep duration over the study period. The Cox proportional hazard model was used to adjust the outcomes based on potential covariates.

RESULTS

Of 15,025 participants, 7,692 (51.2%) were men. The mean age (standard deviation) was 66.0 (7.5) years. During a median follow-up of 2,588 (interquartile range: 1,583-3,695) days, 1,396 (9.3%) participants developed cancer of any type. Compared to hazard ratio in the stable sleep duration group (- 0.1 to + 0.1 h/day in 1 year), both greatly decreased (less than - 0.2 h/day in 1 year; hazard ratio (HR), 2.13; 95% confidence interval (CI), 1.72-2.62) and increased (more than + 0.2 h/day in 1 year; HR, 2.55; 95% CI 2.14-3.04) groups showed significantly higher hazard ratio for the development of any type of cancer.

CONCLUSION

Both increased and decreased sleep duration over time are associated with subsequent cancer development.

Sleep architecture of short sleep time in patients with obstructive sleep apnea: a retrospective single-facility study

PURPOSE

Sleep architecture consists of rapid eye movement (REM) sleep and non-REM sleep time. Non-REM sleep time is further classified into three stages by depth (stage N1-N3). Some studies have reported that short sleep time predicts all-cause mortality. Short sleep time can have characteristics of sleep architecture which contribute to poor prognosis. Obstructive sleep apnea (OSA) is a disease which causes cessation or decline of ventilation during sleep due to upper airway stenosis and affects sleep architecture. Few studies have reported on the sleep architecture of short sleep time in patients with OSA. Therefore, we aimed to observe this phenomenon.

METHODS

From May 2008 to September 2021, patients diagnosed with OSA at our facility were assessed for clinical history and underwent full-night polysomnography (PSG). These patients were classified into two groups: total sleep time (TST) recorded on PSG consisting of a short TST (< 7 h) group and a not short TST (≥ 7 h) group.

RESULTS

Of 266 patients with OSA, compared to the not short TST group (n = 131), the short TST group (n = 135) had a lower REM sleep time (%) and a higher stage N1 sleep time (%). There was a significant difference in age between the two groups, so sub-analyses classified the patients by age: non-elderly patients (< 65 years) and elderly patients (≥ 65 years) to adjust for age. Both sub-analyses showed similar results to the analysis for the combined ages regarding sleep architecture.

CONCLUSION

Patients with OSA who had short sleep time had disordered sleep architecture with a lower REM sleep time (%) and more stage N1 sleep time.

Genetically predicted insomnia and lung cancer risk: a Mendelian randomization study

BACKGROUND

The relationship between insomnia and lung cancer is scanty. The Mendelian randomization approach provides the rationale for evaluating the potential causality between genetically-predicted insomnia and lung cancer risk.

METHODS

We extracted 148 insomnia-related single-nucleotide polymorphisms (SNPs) as instrumental variables (IVs) from published genome-wide association studies (GWASs). Summary data of individual-level genetic information of participants were obtained from the International Lung Cancer Consortium (ILCCO) (29,266 cases and 56,450 controls). MR analyses were performed using the inverse-variance-weighted approach, MR pleiotropy residual sum and outlier (MR-PRESSO) test, weighted median estimator, and MR-Egger regression. Sensitivity analyses were further performed using Egger intercept analysis, leave-one-out analysis, MR-PRESSO global test, and Cochran's Q test to verify the robustness of our findings.

RESULTS

The results of the MR analysis indicated an increased risk of lung cancer in insomnia patients (OR = 1.1671; 95% CI 1.0754-1.2666, p = 0.0002). The subgroup analyses showed increased risks of lung adenocarcinoma (OR = 1.1878; 95% CI 1.0594-1.3317, p = 0.0032) and squamous cell lung cancer (OR = 1.1595; 95% CI 1.0248-1.3119, p = 0.0188).

CONCLUSION

Our study indicated that insomnia is a causal risk factor in the development of lung cancer. Due to the lack of evidence on both the epidemiology and the mechanism level, more studies are needed to better elucidate the results of the study.

Dietary patterns with combined and site-specific cancer incidence in Alberta's Tomorrow Project cohort

BACKGROUND/OBJECTIVES

Poor diet quality has been associated with an increased risk of cancer. Here, we examine the association between dietary patterns derived with two methods, and combined and site-specific cancer incidence in Canada.

SUBJECTS/METHODS

Dietary data were obtained from participants enrolled in Alberta's Tomorrow Project, a prospective cohort study, between 2000 and 2008. Principle component analysis (PCA) and reduced rank regression (RRR) were used to derive dietary patterns, and data linkage with the Alberta Cancer Registry was used for incident cancer cases. Cox proportional hazard regressions were used to estimate multivariable-adjusted models for the association between each dietary pattern score with combined and site-specific cancer incidence.

RESULTS

PCA revealed three dietary patterns ("western", "prudent", and "sugar, fruits, and dairy") and RRR resulted in four patterns ("dietary fiber", "vitamin D", "fructose", and "discretionary fat"). Five cancer sites were included in our site-specific analysis: lung, colon, breast, prostate, and endometrial cancers. The most protective dietary patterns for combined cancer sites were the "Prudent" pattern (HR = 0.82, CI = 0.73-0.92) and the "Dietary fiber" pattern (HR = 0.82, CI = 0.69-0.97). The "Fructose" pattern was associated with increased risk of combined cancers (HR = 1.14, CI = 1.02-1.27). Three dietary patterns were protective against colon cancer ("Prudent", "Dietary fiber", and "Discretionary fats"), and other risk reductions were seen for the "sugar, fruit, and dairy" pattern (lung cancer), and the "Dietary fiber" pattern (prostate cancer).

CONCLUSIONS

These results support cancer prevention strategies for a diet high in vegetables, fruits, fish, and whole grains. Further studies should explore the possible association between discretionary fats and colon cancer.

Association between Sleep Traits and Lung Cancer: A Mendelian Randomization Study

Multidimensional sleep trait, which is related to circadian rhythms closely, affects some cancers predominantly, while the relationship between sleep and lung cancer is rarely illustrated. We aimed to investigate whether sleep is causally associated with risk of lung cancer, through a two-sample Mendelian randomization study. The main analysis used publicly available GWAS summary data from two large consortia (UK Biobank and International Lung Cancer Consortium). Two-sample Mendelian randomization (MR) analysis was used to examine whether chronotype, getting up in the morning, sleep duration, nap during the day, or sleeplessness was causally associated with the risk of lung cancer. Additionally, multivariate MR analysis was also conducted to estimate the direct effects between sleep traits and lung cancer risks independent of smoking status including pack years of smoking or current tobacco smoking. There was no evidence of causal association between chronotype, getting up in the morning, or nap during the day and lung cancer. Sleeplessness was associated with higher risk of lung adenocarcinoma (odds ratio 5.75, 95% confidence intervals 2.12-15.65), while sleep duration played a protective role in lung cancer (0.46, 0.26-0.83). In multivariate MR analysis, sleeplessness and sleep duration remained to have similar results. In conclusion, we found robust evidence for effect of sleeplessness on lung adenocarcinoma risk and inconsistent evidence for a protective effect of sleep duration on lung cancer risk.

Loneliness and social isolation increase cancer incidence in a cohort of Finnish middle-aged men. A longitudinal study

Globally, cancer is the second leading cause of death. Loneliness has been suggested as a risk factor for cancer mortality. However, connections between loneliness, social isolation, and cancer are poorly understood. In our longitudinal study (mean follow-up: 20.44 years) of 2570 middle-aged men, loneliness, social isolation, and health-related factors were measured at baseline. Cox proportional hazards analysis was used to examine the association between cancer incidence, loneliness, and social isolation. The effect of relationship status on cancer mortality among cancer patients was tested with the Kaplan-Meier method. Loneliness was associated with total cancer incidence after adjustments for tested lifestyle and health-related covariates. Social Isolation was associated with total cancer incidence, except when adjusted for lifestyle, diet, or Human Population Laboratory (HPL) Depression Scale scores. Loneliness was associated with lung cancer incidence, except when adjusted for HPL Depression Scale scores. There was no significant association between social isolation and lung cancer. Neither loneliness nor social isolation were connected with prostate or colorectal cancer. Being single at baseline was associated with worse survival outcomes for cancer patients. Our findings suggest that regardless of the social network size, loneliness among middle-aged men is associated with an increased likelihood of cancer.

Relationships of sleep traits with lung cancer risk: a prospective cohort study in UK Biobank

STUDY OBJECTIVES

To prospectively investigate the association between sleep traits and lung cancer risk, accounting for the interactions with genetic predisposition of lung cancer.

METHODS

We included 469,691 individuals free of lung cancer at recruitment from UK Biobank, measuring sleep behaviors with a standardized questionnaire and identifying incident lung cancer cases through linkage to national cancer and death registries. We estimated multivariable adjusted hazard ratios (HR) for lung cancer (2,177 incident cases) across four sleep traits (sleep duration, chronotype, insomnia and snoring), and examined the interaction and joint effects with a lung cancer polygenic risk score.

RESULTS

A U-shaped association was observed for sleep duration and lung cancer risk, with a 18% higher risk (95% confidence interval (CI): 1.07-1.30) for short sleepers and a 17% higher risk (95%CI: 1.02-1.34) for long sleepers compared with normal sleepers (7-8 h/day). Evening preference was associated with elevated lung cancer risk compared with morning preference (HR: 1.25; 95%CI: 1.07-1.46), but no association was found for insomnia or snoring. Compared to participants with favorable sleep traits and low genetic risk, those with both unfavorable sleep duration (<7 hours or >8 hours) or evening preference and high genetic risk showed the greatest lung cancer risk (HRsleep duration: 1.83; 95%CI: 1.47-2.27; HRchronotype: 1.85; 95%CI: 1.34-2.56).

CONCLUSIONS

Both unfavorable sleep duration and evening chronotype were associated with increased lung cancer incidence, especially for those with low to moderate genetic risk. These results indicate that sleep behaviors as modifiable risk factors may have potential implications for lung cancer risk.

Sleep duration and breast cancer incidence: results from the Million Women Study and meta-analysis of published prospective studies

STUDY OBJECTIVES

To investigate the association between sleep duration and breast cancer incidence, we examined the association in a large UK prospective study and conducted a meta-analysis of prospective studies.

METHODS

In the Million Women Study, usual sleep duration over a 24-h period was collected in 2001 for 713,150 participants without prior cancer, heart problems, stroke, or diabetes (mean age = 60 years). Follow-up for breast cancer was by record linkage to national cancer registry data for 14.3 years on average from the 3-year resurvey. Cox regression models yielded multivariable-adjusted breast cancer relative risks (RR) and 95% confidence intervals (CIs) for sleep duration categories. Published prospective studies of sleep duration and breast cancer risk were included in a meta-analysis, which estimated the inverse-variance weighted average of study-specific log RRs for short and for long versus average duration sleep.

RESULTS

After excluding the first 5 years to minimize reverse causation bias in the Million Women Study, 24,476 women developed breast cancer. Compared with 7-8 h of sleep, the RRs for <6, 6, 9, and >9 h of sleep were 1.01 (95% CI, 0.95-1.07), 0.99 (0.96-1.03), 1.01 (0.96-1.06), and 1.03 (0.95-1.12), respectively. In a meta-analysis of 14 prospective studies plus the Million Women Study, including 65,410 breast cancer cases, neither short (RR < 7 h = 0.99 [0.98-1.01]) nor long (RR > 8 h = 1.01 [0.98-1.04]) versus average duration sleep was associated with breast cancer risk.

CONCLUSIONS

The totality of the prospective evidence does not support an association between sleep duration and breast cancer risk.

Social Jetlag and Prostate Cancer Incidence in Alberta's Tomorrow Project: A Prospective Cohort Study

We investigated the association of social jetlag (misalignment between the internal clock and socially required timing of activities) and prostate cancer incidence in a prospective cohort in Alberta, Canada. Data were collected from 7455 cancer-free men aged 35-69 years enrolled in Alberta's Tomorrow Project (ATP) from 2001-2007. In the 2008 survey, participants reported usual bed- and wake-times on weekdays and weekend days. Social jetlag was defined as the absolute difference in waking time between weekday and weekend days, and was categorized into three groups: 0-<1 h (from 0 to anything smaller than 1), 1-<2 h (from 1 to anything smaller than 2), and 2+ h. ATP facilitated data linkage with the Alberta Cancer Registry in June 2018 to determine incident prostate cancer cases (n = 250). Hazard ratios (HR) were estimated using Cox proportional hazards regressions, adjusting for a range of covariates. Median follow-up was 9.57 years, yielding 68,499 person-years. Baseline presence of social jetlag of 1-<2 h (HR = 1.52, 95% CI: 1.10 to 2.01), and 2+ hours (HR = 1.69, 95% CI: 1.15 to 2.46) were associated with increased prostate cancer risk vs. those reporting no social jetlag (p for trend = 0.004). These associations remained after adjusting for sleep duration (p for trend = 0.006). With respect to chronotype, the association between social jetlag and prostate cancer risk remained significant in men with early chronotypes (p for trend = 0.003) but attenuated to null in men with intermediate (p for trend = 0.150) or late chronotype (p for trend = 0.381). Our findings suggest that greater than one hour of habitual social jetlag is associated with an increased risk of prostate cancer. Longitudinal studies with repeated measures of social jetlag and large samples with sufficient advanced prostate cancer cases are needed to confirm these findings.

The Association of Sleep Disorders, Obesity and Sleep-Related Hypoxia with Cancer

BACKGROUND

Sleep disorders have emerged as potential cancer risk factors.

OBJECTIVE

This review discusses the relationships between sleep, obesity, and breathing disorders with concomitant risks of developing cancer.

RESULTS

Sleep disorders result in abnormal expression of clock genes, decreased immunity, and melatonin release disruption. Therefore, these disorders may contribute to cancer development. Moreover, in sleep breathing disorder, which is frequently experienced by obese persons, the sufferer experiences intermittent hypoxia that may stimulate cancer cell proliferation.

DISCUSSION

During short- or long- duration sleep, sleep-wake rhythm disruption may occur. Insomnia and obstructive sleep apnea increase cancer risks. In short sleepers, an increased risk of stomach cancer, esophageal squamous cell cancer, and breast cancer was observed. Among long sleepers (>9 hours), the risk of some hematologic malignancies is elevated.

CONCLUSION

Several factors including insomnia, circadian disruption, obesity, and intermittent hypoxia in obstructive sleep apnea are contributing risk factors for increased risk of several types of cancers. However, further studies are needed to determine the more significant of these risk factors and their interactions.