Association between sleep duration and cancer risk: a meta-analysis of prospective cohort studies

Sex-specific associations between habitual snoring and cancer prevalence: insights from a US Cohort Study

Study Objectives

To investigate the sex-specific association between habitual snoring and overall cancer prevalence and subtypes, and to examine the influence of age, body mass index (BMI), and sleep duration on this association.

Methods

This study utilized data from the National Health and Nutrition Examination Survey cycles between 2005 and 2020 and included 15 892 participants aged 18 and over. We employed inverse probability of treatment weighting based on propensity scores to adjust for confounders when comparing the prevalence of cancer between habitual snorers and non-habitual snorers for each sex and cancer type. Subgroup analyses were conducted based on sleep duration, age, and BMI categories.

Results

The cohort (mean age 48.2 years, 50.4% female, and 30.5% habitual snorers) reported 1385 cancer cases. In men, habitual snoring was linked to 26% lower odds of any cancer (OR 0.74, 95% CI: 0.66 to 0.83), while in women, it showed no significant difference except lower odds of breast cancer (OR 0.77, 95% CI: 0.63 to 0.94) and higher odds of cervix cancer (OR 1.54, 95% CI: 1.18 to 2.01). Age and sleep duration significantly influenced the snoring-cancer relationship, with notable variations by cancer type and sex.

Conclusions

Habitual snoring exhibits sex-specific associations with cancer prevalence, showing lower prevalence in men and varied results in women. These findings emphasize the critical need for further research to uncover the biological mechanisms involved. Future investigations should consider integrating sleep characteristics with cancer prevention and screening strategies, focusing on longitudinal research and the integration of genetic and biomarker analyses to fully understand these complex relationships.

Prospective analysis of sleep characteristics, chronotype, and risk of breast cancer in the california teachers study

PURPOSE

Poor sleep quality and evening chronotype were associated with increased risk of breast cancer in a previous retrospective study in the California Teachers Study (CTS). The present analysis examines these sleep factors prospectively in the same cohort of women.

METHODS

From the CTS, we included 1,085 incident breast cancer cases and 38,470 cancer-free participants from 2012 through 2019. We calculated time at risk and used Cox proportional hazards regression models to estimate the hazard ratios (HRs) and control for risk factors such as age, race, body mass index, family history of breast cancer, and reproductive history. The sleep factors examined were quality, latency, duration, disturbance, and sleep medication use, based on a shortened version of the Pittsburgh Sleep Quality Index, as well as chronotype (preference for morning or evening activity). This analysis was limited to women who were post-menopausal at the time they answered these sleep-related questions.

RESULTS

Measures of sleep quality did not appear to be associated with subsequent breast cancer risk. The HR for evening chronotypes compared to morning chronotypes was somewhat elevated (HR 1.19, 95% CI 1.04, 1.36).

CONCLUSION

While the measures of sleep quality and duration were not associated with post-menopausal breast cancer risk in this prospective analysis, the modestly elevated risk observed for evening chronotypes was consistent with the prior retrospective analysis.

Age Differences in the Association of Sleep Duration Trajectory With Cancer Risk and Cancer-Specific Mortality: Prospective Cohort Study

BACKGROUND

Baseline sleep duration is associated with cancer risk and cancer-specific mortality; however, the association between longitudinal patterns of sleep duration and these risks remains unknown.

OBJECTIVE

This study aimed to elucidate the association between sleep duration trajectory and cancer risk and cancer-specific mortality.

METHODS

The participants recruited in this study were from the Kailuan cohort, with all participants aged between 18 and 98 years and without cancer at baseline. The sleep duration of participants was continuously recorded in 2006, 2008, and 2010. Latent mixture modeling was used to identify shared sleep duration trajectories. Furthermore, the Cox proportional risk model was used to examine the association of sleep duration trajectory with cancer risk and cancer-specific mortality.

RESULTS

A total of 53,273 participants were included in the present study, of whom 40,909 (76.79%) were men and 12,364 (23.21%) were women. The average age of the participants was 49.03 (SD 11.76) years. During a median follow-up of 10.99 (IQR 10.27-11.15) years, 2705 participants developed cancers. Three sleep duration trajectories were identified: normal-stable (44,844/53,273, 84.18%), median-stable (5877/53,273, 11.03%), and decreasing low-stable (2552/53,273, 4.79%). Compared with the normal-stable group, the decreasing low-stable group had increased cancer risk (hazard ratio [HR] 1.39, 95% CI 1.16-1.65) and cancer-specific mortality (HR 1.54, 95% CI 1.18-2.06). Dividing the participants by an age cutoff of 45 years revealed an increase in cancer risk (HR 1.88, 95% CI 1.30-2.71) and cancer-specific mortality (HR 2.52, 95% CI 1.22-5.19) only in participants younger than 45 years, rather than middle-aged or older participants. Joint analysis revealed that compared with participants who had a stable sleep duration within the normal range and did not snore, those with a shortened sleep duration and snoring had the highest cancer risk (HR 2.62, 95% CI 1.46-4.70).

CONCLUSIONS

Sleep duration trajectories and quality are closely associated with cancer risk and cancer-specific mortality. However, these associations differ with age and are more pronounced in individuals aged <45 years.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR-TNRC-11001489; http://tinyurl.com/2u89hrhx.

Neuropsychiatric adverse drug reactions with oral tyrosine kinase inhibitors in metastatic colorectal cancer: an analysis from the FDA Adverse Event Reporting System

Introduction

New oral tyrosine kinase inhibitors (TKIs) are approved for metastatic colorectal cancer (mCRC). The aim of this study was to assess the neuropsychiatric adverse drug reactions (ADRs) of these drugs reported in the FDA Adverse Event Reporting System (FAERS) database.

Methods

All reports with regorafenib (REG) and encorafenib (ENC) as the primary suspect, and reported in the FAERS between 2012 and 2022, were collected. A descriptive and disproportionality analyses were conducted.

Results

Out of 4,984 cases, 1,357 (30.2%) reported at least one neuropsychiatric ADR. New potential signals for REG included neuropathy peripheral (n = 265; reporting odds ratio, ROR = 19.48, 95% confidence interval, CI 95% = 17.52-22.47; information component, IC = 2.89, IC025-IC075 = 2.77-3.02), hyperesthesia (n = 18; ROR = 12.56, CI 95% = 7.90-19.96; IC = 2.25, IC025-IC075 = 1.79-2.72), taste disorder (n = 41; ROR = 9.91, CI 95% = 7.29-13.49; IC = 2.18, IC025-IC075 = 1.88-2.49), poor quality sleep (n = 18; ROR = 6.56, CI 95% = 4.13-10.42; IC = 1.74, IC025-IC075 = 1.27-2.20), altered state of consciousness (n = 15; ROR = 5.50, CI 95% = 3.31-9.14; IC = 1.57, IC025-IC075 = 1.06-2.07), depressed mood (n = 13; ROR = 1.85, CI 95% = 1.07-3.19; IC = 0.58, IC025-IC075 = 0.04-1.13) and insomnia (n = 63; ROR = 1.48, CI 95% = 1.15-1.89; IC = 0.38, IC025-IC075 = 0.13-0.63). For ENC comprised depressed mood (n = 4; ROR = 5.75, CI 95% = 2.15-15.39; IC = 1.74, IC025-IC075 = 0.76-2.73) and cognitive disorders (n = 3; ROR = 4.71, CI 95% = 1.51-14.66; IC = 1.54, IC025-IC075 = 0.41-2.68).

Discussion

This study identified new unknown potential neuropsychiatric ADRs. Further investigations are required to better define the neurotoxicity of TKIs in mCRC patients.

Risk factors for insomnia and burnout: A longitudinal population-based cohort study

Insomnia and burnout are highly prevalent in the general population, calling for understanding of its causes. Taking a broad approach, the aim of this study was to determine various mental and somatic risk factors for development of insomnia and burnout and stratifying for sex and age group. Questionnaire data were used from a Swedish population-based sample aged 18-79 years, from which cohorts without insomnia (n = 1702) and without burnout (n = 1972) at baseline were followed-up after 3 years. Self-reports of eight mental and somatic conditions at baseline were used as independent variables in logistic regression analyses to predict development of insomnia and burnout at 3-year follow-up. All eight studied conditions were significant risk factors for development of both insomnia (odds ratio, OR = 1.62-2.73) and burnout (OR = 2.20-3.21). Burnout and poor self-rated health had the highest ORs for insomnia, and poor self-rated health, anxiety and somatic symptoms had the highest ORs for burnout. The ORs were generally similar between men and women, whereas age groups tended to differ in some of the risk factors. The study highlights the importance of a broad assessment of both mental and somatic conditions in the prevention of insomnia and burnout.

Sleep and cancer recurrence and survival in patients with resected Stage III colon cancer: findings from CALGB/SWOG 80702 (Alliance)

BACKGROUND

We sought to assess the influences of sleep duration, sleep adequacy, and daytime sleepiness on survival outcomes among Stage III colon cancer patients.

METHODS

We conducted a prospective observational study of 1175 Stage III colon cancer patients enrolled in the CALGB/SWOG 80702 randomised adjuvant chemotherapy trial who completed a self-reported questionnaire on dietary and lifestyle habits 14-16 months post-randomisation. The primary endpoint was disease-free survival (DFS), and secondary was overall survival (OS). Multivariate analyses were adjusted for baseline sociodemographic, clinical, dietary and lifestyle factors.

RESULTS

Patients sleeping ≥9 h-relative to 7 h-experienced a worse hazard ratio (HR) of 1.62 (95% confidence interval (CI), 1.01-2.58) for DFS. In addition, those sleeping the least (≤5 h) or the most (≥ 9 h) experienced worse HRs for OS of 2.14 (95% CI, 1.14-4.03) and 2.34 (95% CI, 1.26-4.33), respectively. Self-reported sleep adequacy and daytime sleepiness showed no significant correlations with outcomes.

CONCLUSIONS

Among resected Stage III colon cancer patients who received uniform treatment and follow-up within a nationwide randomised clinical trial, very long and very short sleep durations were significantly associated with increased mortality. Interventions targeting optimising sleep health among indicated colon cancer patients may be an important method by which more comprehensive care can be delivered.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01150045.

Incidence disparities of obstructive sleep apnea-associated lung cancer by gender; Korean National Health Insurance data analysis

Introduction

Obstructive sleep apnea (OSA) is known to increase the risk of various cancers. By analyzing the Korea National Health Insurance Service (KNHIS) registry, the impact of OSA on the lung cancer incidence was analyzed in a retrospective cohort group.

Methods

A retrospective cohort of adult patients newly registered with OSA in the KNHIS data from 2007 to 2017 was included and observed until December 2019 (12 years). The main outcome measure was newly diagnosed lung cancer. The control group was set with age and sex that matched those in the OSA group.

Results

The hazard ratio (HR) of OSA for lung cancer incidence showed a significantly reduced HR of 0.87 (95% CI, 0.82-0.93). The observed significance of this finding was limited to male OSA patients [HR, 0.84 (95% CI, 0.78-0.90)], while no significant association was found in female OSA patients [HR, 1.05 (95% CI, 0.91-1.21)], irrespective of their age.

Discussion

OSA patients have a lower risk of developing lung cancer, but this risk reduction is gender-specific, as female OSA patients do not show a reduction in hazard ratio.

Leveraging genetic discoveries for sleep to determine causal relationships with common complex traits

Sleep occurs universally and is a biological necessity for human functioning. The consequences of diminished sleep quality impact physical and physiological systems such as neurological, cardiovascular, and metabolic processes. In fact, people impacted by common complex diseases experience a wide range of sleep disturbances. It is challenging to uncover the underlying molecular mechanisms responsible for decreased sleep quality in many disease systems owing to the lack of suitable sleep biomarkers. However, the discovery of a genetic component to sleep patterns has opened a new opportunity to examine and understand the involvement of sleep in many disease states. It is now possible to use major genomic resources and technologies to uncover genetic contributions to many common diseases. Large scale prospective studies such as the genome wide association studies (GWAS) have successfully revealed many robust genetic signals associated with sleep-related traits. With the discovery of these genetic variants, a major objective of the community has been to investigate whether sleep-related traits are associated with disease pathogenesis and other health complications. Mendelian Randomization (MR) represents an analytical method that leverages genetic loci as proxy indicators to establish causal effect between sleep traits and disease outcomes. Given such variants are randomly inherited at birth, confounding bias is eliminated with MR analysis, thus demonstrating evidence of causal relationships that can be used for drug development and to prioritize clinical trials. In this review, we outline the results of MR analyses performed to date on sleep traits in relation to a multitude of common complex diseases.

Relationships of sleep traits with prostate cancer risk: A prospective study of 213,999 UK Biobank participants

BACKGROUND

The effect of sleep on the occurrence of prostate cancer (PCa) remains unclear. This study explored the influence of sleep traits on the incidence of PCa using a UK Biobank cohort study.

METHODS

In this prospective cohort study, 213,999 individuals free of PCa at recruitment from UK Biobank were included. Missing data were imputed using multiple imputation by chained equations. Cox proportional hazards models were used to calculate the adjusted hazard ratios and 95% confidence intervals for PCa (6747 incident cases) across seven sleep traits (sleep duration, chronotype, insomnia, snoring, nap, difficulty to get up in the morning, and daytime sleepiness). In addition, we newly created a healthy sleep quality score according to sleep traits to assess the impact of the overall status of night and daytime sleep on PCa development. E values were used to assess unmeasured confounding.

RESULTS

We identified 6747 incident cases, of which 344 died from PCa. Participants who usually suffered from insomnia had a higher risk of PCa (hazard ratio [HR]: 1.11; 95% confidence interval [CI]: 1.04-1.19, E value: 1.46). Finding it fairly easy to get up in the morning was also positively associated with PCa (HR: 1.09; 95% CI: 1.04-1.15, E value: 1.40). Usually having a nap was associated with a lower risk of PCa (HR: 0.91; 95% CI: 0.83-0.99, E value: 1.42).

CONCLUSIONS

Fairly easy to get up in the morning and usually experiencing insomnia were associated with an increased incidence of PCa. Moreover, usually having a nap was associated with a lower risk of PCa. Therefore, sleep behaviors are modifiable risk factors that may have a potential impact on PCa risk.

Impact of Rotating Shifts on Lifestyle Patterns and Perceived Stress among Nurses: A Cross-Sectional Study

Although rotating shifts have a negative health impact, their association with hospital nurses’ health risks remains controversial due to incomplete adjustment in lifestyle patterns and heterogeneity of work schedules. However, whether work schedule characteristics are associated with lifestyle patterns and perceived stress remains undetermined. We assessed the correlations of work schedule characteristics, lifestyle patterns, and perceived stress among hospital nurses. This cross-sectional study included 340 nurses from two hospitals. Final data from 329 nurses regarding work schedule characteristics, lifestyle patterns (physical activity, dietary behavior, and sleep pattern), and perceived stress were analyzed via linear regression models. Fixed-day-shift nurses had reduced perceived stress (β = 0.15, p = 0.007) compared with rotating-shift nurses. Additionally, among rotating-shift nurses, fixed-evening- and fixed-night-shift nurses had longer sleep duration (β = 0.27, p < 0.001; β = 0.25, p < 0.001) compared to non-fixed-rotating-shift nurses. Longer rotating-shift work was associated with healthier dietary behaviors (β = 0.15, p = 0.008), better sleep quality (β = −0.17, p = 0.003), lower perceived stress (β = −0.24, p < 0.001), and shorter sleep duration (β = −0.17, p = 0.003). Hospital nurses’ work schedule characteristics were associated with lifestyle patterns, dietary behavior, sleep pattern, and perceived stress. Fixed-shifts were beneficial for lifestyle and lower perceived stress. Longer rotating shifts could help nurses adjust their lifestyles accordingly.

Sleep Duration/Quality With Health Outcomes: An Umbrella Review of Meta-Analyses of Prospective Studies

Background

To quantitatively evaluate the evidence of duration and quality of sleep as measured by multiple health outcomes.

Methods

This review is registered with PROSPERO, number CRD42021235587. We systematically searched three databases from inception until November 15, 2020. For each meta-analysis, the summary effect size using fixed and random effects models, the 95% confidence interval, and the 95% prediction interval were assessed; heterogeneity, evidence of small-study effects, and excess significance bias were also estimated. According to the above metrics, we evaluated the credibility of each association.

Results

A total of 85 meta-analyses with 36 health outcomes were included in the study. We observed highly suggestive evidence for an association between long sleep and an increased risk of all-cause mortality. Moreover, suggestive evidence supported the associations between long sleep and 5 increased risk of health outcomes (stroke, dyslipidaemia, mortality of coronary heart disease, stroke mortality, and the development or death of stroke); short sleep and increased risk of overweight and/or obesity; poor sleep quality and increased risk of diabetes mellitus and gestational diabetes mellitus.

Conclusions

Only the evidence of the association of long sleep with an increased risk of all-cause mortality was graded as highly suggestive. Additional studies are needed to be conducted.

Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42021235587

The Relationship Between Primary Sleep Disorders and Temporomandibular Disorders: An 8-Year Nationwide Cohort Study in South Korea

Background

While evidence is accumulating to propose a specific contribution of sleep disorders and low quality sleep in the pathogenesis of temporomandibular disorders (TMD), management of primary sleep disorders in the process of preventing and treating TMD still remains scientifically unsupported.

Objective

To investigate the association of primary sleep disorders with TMD risk in South Korea.

Patients and Methods

This study was based on the National Health Insurance Service-National Health Screening Cohort (NHIS-HEALS) of South Korea with 468,882 participants. After excluding participants diagnosed in 2002, those with a diagnosis of a primary sleep disorder in 2003–2005 were recruited. All participants diagnosed with TMD between January 1, 2006 and December 31, 2013 received follow-up. Cox proportional hazards regression was performed to determine the adjusted hazard ratios (aHR) and 95% confidence interval (CI) for TMD according to the presence or absence of a primary sleep disorder diagnosis.

Results

After adjusting for all covariates, primary sleep disorder patients had a 44% higher risk for TMD compared with non-sleep disorder participants (aHR 1.44, 95% CI 1.02–2.04). The incidence rate of TMD was nearly twice as high in participants with sleep disorders compared with those without (6.08 vs 3.27, per 10⁴ person-years). In subgroup analysis, an association was observed with those over 60 years old or who frequently exercised physically.

Conclusion

Primary sleep disorders could be an important independent risk factor for the initiation and maintenance of TMD. Patients with sleep disorders should be monitored for possible co-occurrence of TMD-related symptoms that could aggravate sleep disorders in turn.

Sleep duration and risk of overall and 22 site-specific cancers: A Mendelian randomization study

Studies of sleep duration in relation to the risk of site-specific cancers other than breast cancer are scarce. Furthermore, the available results are inconclusive and the causality remains unclear. We aimed to investigate the potential causal associations of sleep duration with overall and site-specific cancers using the Mendelian randomization (MR) design. Single-nucleotide polymorphisms associated with the sleep traits identified from a genome-wide association study were used as instrumental variables to estimate the association with overall cancer and 22 site-specific cancers among 367 586 UK Biobank participants. A replication analysis was performed using data from the FinnGen consortium (up to 121 579 individuals). There was suggestive evidence that genetic liability to short-sleep duration was associated with higher odds of cancers of the stomach (odds ratio [OR], 2.22; 95% confidence interval [CI], 1.15-4.30; P = .018), pancreas (OR, 2.18; 95% CI, 1.32-3.62; P = .002) and colorectum (OR, 1.48; 95% CI, 1.12-1.95; P = .006), but with lower odds of multiple myeloma (OR, 0.47; 95% CI, 0.22-0.99; P = .047). Suggestive evidence of association of genetic liability to long-sleep duration with lower odds of pancreatic cancer (OR, 0.44; 95% CI, 0.25-0.79; P = .005) and kidney cancer (OR, 0.44; 95% CI, 0.21-0.90; P = .025) was observed. However, none of these associations passed the multiple comparison threshold and two-sample MR analysis using FinnGen data did not confirm these findings. In conclusion, this MR study does not provide strong evidence to support causal associations of sleep duration with risk of overall and site-specific cancers. Further MR studies are required.

Sleep deficiency and breast cancer risk among postmenopausal women in the California teachers study (CTS)

PURPOSE

There is provocative, yet inconsistent, evidence that sleep deficiency may influence the development of breast cancer. The purpose of this study was to evaluate the risk of breast cancer associated with sleep deficiency among postmenopausal women in the California Teachers Study (CTS).

METHODS

We conducted a case-control study of 2,856 invasive breast cancer cases and 38,649 cancer-free controls, nested within the CTS. Self-administered questionnaires were used to ascertain several components of sleep deficiency, including quality, latency, duration, disturbance and use of sleep medications. Additionally, a Global Sleep Index (GSI) was created by summing the individual sleep components and categorizing into quartiles. Multivariable logistic regression analyses were used to estimate odds ratios and 95% confidence intervals (OR, 95% CI).

RESULTS

Increased breast cancer risks were associated with sleep deficiency. With the exception of duration, linear increases in risk were associated with all the other individual components of sleep deficiency (p-trend ≤ 0.002). The OR for the highest GSI quartile vs. lowest was 1.24, 95% CI 1.12-1.38; p-trend < 0.001).

CONCLUSIONS

Sleep deficiency may be a risk factor for breast cancer. Additional prospective studies and those aimed at elucidating underlying mechanism are warranted.

Sleep quality and prostate cancer aggressiveness: Results from the REDUCE trial

BACKGROUND

Disrupted sleep has been associated with increased risk of certain cancers. Little data exist in prostate cancer. We tested the association between sleep quality and prostate cancer diagnosis overall and by tumor grade in the Reduction by Dutasteride of Prostate Cancer Events chemoprevention trial. We hypothesized that worse sleep quality would be associated with increased tumor aggressiveness.

METHODS

At baseline, 5614 men completed a validated six-item questionnaire on sleep quality. We generated a composite score categorized into tertiles to measure overall sleep quality and assessed each sleep quality question individually. Logistic regression was used to test associations between baseline sleep quality and overall, low-grade and high-grade prostate cancer diagnosis at 2-year study-mandated biopsy. Models were stratified by nocturia.

RESULTS

Overall sleep quality was unrelated to overall or low-grade prostate cancer. Worse overall sleep quality was associated with elevated odds of high-grade prostate cancer (odds ratio [OR]_T3vsT1 1.15; 95% confidence interval [CI]: 0.83-1.60 and OR_T2vsT1 1.39; 95% CI: 1.01-1.92). Men reporting trouble falling asleep at night sometimes vs never had elevated odds of high-grade prostate cancer (OR: 1.51; 95% CI: 1.08-2.09) while trouble staying awake during the day was associated with decreased odds of low-grade prostate cancer (OR: 0.65; 95% CI: 0.49-0.86). Results were similar within strata of nocturia severity.

CONCLUSIONS

Overall, associations between sleep quality and prostate cancer were inconsistent. However, there was some evidence for a positive association between insomnia and high-grade prostate cancer, and an inverse relationship between daytime sleepiness and low-grade prostate cancer; findings that should be validated by future studies.

The future of sleep health: a data-driven revolution in sleep science and medicine

In recent years, there has been a significant expansion in the development and use of multi-modal sensors and technologies to monitor physical activity, sleep and circadian rhythms. These developments make accurate sleep monitoring at scale a possibility for the first time. Vast amounts of multi-sensor data are being generated with potential applications ranging from large-scale epidemiological research linking sleep patterns to disease, to wellness applications, including the sleep coaching of individuals with chronic conditions. However, in order to realise the full potential of these technologies for individuals, medicine and research, several significant challenges must be overcome. There are important outstanding questions regarding performance evaluation, as well as data storage, curation, processing, integration, modelling and interpretation. Here, we leverage expertise across neuroscience, clinical medicine, bioengineering, electrical engineering, epidemiology, computer science, mHealth and human-computer interaction to discuss the digitisation of sleep from a inter-disciplinary perspective. We introduce the state-of-the-art in sleep-monitoring technologies, and discuss the opportunities and challenges from data acquisition to the eventual application of insights in clinical and consumer settings. Further, we explore the strengths and limitations of current and emerging sensing methods with a particular focus on novel data-driven technologies, such as Artificial Intelligence.

Sleep duration and risk of all-cause mortality: a systematic review and meta-analysis

AIMS

To determine the association between the sleep duration and the risk of all-cause mortality in adults.

METHODS

A search strategy was conducted in the MEDLINE, CENTRAL, EMBASE and LILACS databases. Searches were also conducted in other databases and unpublished literature. Cohort studies were included without language, time or setting restrictions. The risk of bias was evaluated with a modified Cochrane Collaboration's tool. An analysis of random effects was conducted. The primary outcome was all-cause mortality. The measure of the effect was the risk difference (RD) with a 95% confidence interval (CI). The planned comparisons were 7-9 h of sleep v. <7 h and the same reference v. >9 h.

RESULTS

Thirty-nine studies were included in our qualitative analysis, regarding the quantitative analysis, 19 studies were included in <7 v. 7-9 h analysis, and 18 studies in the >9 v. 7-9 h. A low risk of bias was shown for most of the study items. The overall RD for all-cause mortality was 0.09 (95% CI 0.07-0.11) favouring the >9 h group compared with our reference. In contrast, no differences were found between the <7 h and the reference sleep duration groups (RD 0.00, 95% CI 0.00-0.01).

CONCLUSION

We found a probable association of long sleep duration and higher mortality; however, it could reflect an underlying systemic or neurological disease that cause sleep fragmentation, deterioration in quality and micro-awakenings.

The Association Between Sleep Disorders and the Risk of Colorectal Cancer in Patients: A Population-based Nested Case-Control Study

AIM

To investigate the risk of colorectal cancer in patients with sleep disorders.

MATERIALS AND METHODS

We identified 7,355 participants with colorectal cancer between January 1, 2000, and December 31, 2013, from the Longitudinal Health Insurance Database 2005 of the Taiwan National Health Insurance Research Database; 29,420 controls were also identified from the same database based on frequency matching on age, sex, and index date of the cases. Diagnoses of sleep disorders by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) in the cases and controls prior to the index date were assessed. The risk of colorectal cancer in patients with sleep disorders was estimated with multivariate logistic regression analyses.

RESULTS

The mean age of the 36,775 patients was 63.05 years, and 56% of them were males. The risk of colorectal cancer was higher in patients with sleep disorders compared to those without [adjusted odds ratio (OR)=1.29, 95% confidence interval (CI)=1.13-1.47]. The risk of colorectal cancer was higher in patients having sleep disorders with depression compared to those without the condition (adjusted OR=5.69, 95% CI=4.01-6.98).

CONCLUSION

The risk of colorectal cancer in patients with sleep disorders was found to be significantly higher by case-control study and particularly pronounced among those with sleep disorders with depression, exhibiting a joint effect on colorectal cancer risk.

Association between sleep problems and health-related quality of life in Canadian adults with chronic diseases

OBJECTIVES

This study aimed to explore the association between sleep problems and health-related quality of life (HRQoL) in Canadian adults with chronic diseases, and whether mental illness can mediate the association.

METHODS

Data were drawn from the Canadian Community Health Survey, 2015. A total of 10,900 participants aged ≥18 years and diagnosed with chronic diseases were enrolled in this study.

RESULTS

Of these participants, 23.6% (95% CI 22.1, 25.2) suffered from severe impairment of HRQoL. Extreme sleep durations, including both short (<5, 5 to <6, and 6 to <7 h) and long (9 to <10, and ≥10 h) sleep durations, were significantly associated with severe impairment of HRQoL (compared to 7 to <8 h). Insomnia was also independently associated with severe impairment of HRQoL when compared to those without insomnia. In the mediation analyses, mental illness was shown to partly mediate the associations of extreme sleep durations and insomnia with severe impairment of HRQoL.

CONCLUSIONS

In conclusion, both extreme sleep durations and insomnia were independently associated with severe impairment of HRQoL in adults with chronic diseases, and mental illness partly mediated the association.

Sleep duration and the risk of cancer: a systematic review and meta-analysis including dose-response relationship

Background

The effect of sleep duration on cancer risk remains controversial. We aimed to quantify the available evidence on this relationship using categorical and dose–response meta-analyses.

Methods

Population-based cohort studies and case-control studies with at least three categories of sleep duration were identified by searching PubMed, EMBASE, and the Cochrane Library database up to July 2017.

Results

Sixty-five studies from 25 articles were included, involving 1,550,524 participants and 86,201 cancer cases. The categorical meta-analysis revealed that neither short nor long sleep duration was associated with increased cancer risk (short: odds ratio [OR] = 1.01, 95% confidence intervals [CI] = 0.97–1.05; long: OR = 1.02, 95% CI = 0.97–1.07). Subgroup analysis revealed that short sleep duration was associated with cancer risk among Asians (OR = 1.36; 95% CI: 1.02–1.80) and long sleep duration significantly increased the risk of colorectal cancer (OR = 1.21; 95% CI: 1.08–1.34). The dose–response meta-analysis showed no significant relationship between sleep duration and cancer risk. When treated as two linear piecewise functions with a cut point of 7 h, similar nonsignificant associations were found (per 1-h reduction: OR = 1.02, 95% CI = 0.98–1.07; per 1-h increment: OR = 1.003, 95% CI = 0.97–1.03).

Conclusion

Categorical meta-analysis indicated that short sleep duration increased cancer risk in Asians and long sleep duration increased the risk of colorectal cancer, but these findings were not consistent in the dose–response meta-analysis. Long-term randomized controlled trials and well-designed prospective studies are needed to establish causality and to elucidate the mechanism underlying the association between sleep duration and cancer risk.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5025-y) contains supplementary material, which is available to authorized users.

Sleep lengthening in late adulthood signals increased risk of mortality

Study Objectives

Epidemiological evidence indicates that both short and long sleep at midlife increase mortality risk, but few studies have examined how change in sleep duration between midlife and later life affects this risk. We examined the association between change in sleep duration and mortality risk.

Methods

The Singapore Chinese Health Study is a prospective cohort of 63257 Chinese in Singapore aged 45-74 years at recruitment (1993-1998). Self-reported sleep duration was collected from 39523 participants who completed both baseline (mean age 54.8 years) and follow-up II (mean age 67.9 years; 2006-2010) interviews, which were on average 12.7 years apart. Mortality data were obtained via linkage with national death registry up to December 31, 2015.

Results

Compared with participants who reported sleeping the recommended duration (7 hr) at both interviews, those with persistently short sleep (≤5 hr) had increased risk of all-cause mortality (hazard ratio [HR] 1.27, 95% confidence interval [CI] 1.06-1.53). Similarly, those with persistently long sleep (≥9 hr) had increased risk of all-cause (HR 1.47, 95% CI 1.24-1.73) and cardiovascular (HR 1.40, 95% CI 1.04-1.89) mortality. The proportion of long-sleepers increased with aging (6%-23.7%). Progression to long sleep from short (HR 1.50, 95% CI 1.24-1.81) or recommended (HR 1.43, 95% CI 1.25-1.64) duration was associated with increased all-cause mortality, especially for cardiovascular mortality. Change in sleep duration was not linked to cancer mortality.

Conclusions

Persistent short or long sleep or increasing sleep duration in late adulthood was associated with increased risk of all-cause mortality, especially from cardiovascular causes.

Sleep Duration and Risk of Liver Cancer in Postmenopausal Women: The Women's Health Initiative Study

BACKGROUND

Sleep duration has been associated with nonalcoholic fatty liver disease, but its association with liver cancer remains unknown.

MATERIAL AND METHODS

In the prospective Women's Health Initiative Study, 139,368 postmenopausal women reported sleep habits at baseline (1993-1998). We ascertained 175 incident liver cancer cases during an average 13.8 years of follow-up through August 2014. We used multivariable Cox proportional hazard regression models to estimate a hazard ratio (HR) and its 95% confidence interval (95% CI) for risk of liver cancer in association with nocturnal sleep duration.

RESULTS

Compared to women reporting 6-8 hours of sleep, the HR for liver cancer was 1.94 (95% CI 1.07-3.53) for women reporting ≥9 hours of sleep. Among the obese women, the HR associated with ≥9 hours of sleep was 3.18 (95% CI 1.84-8.60). The HR was 0.93 (95% CI 0.34-2.53) among nonobese women (p value for interaction = 0.18). Short sleep duration (≤5 hours) was not associated with liver cancer risk.

CONCLUSION

Long sleep duration was associated with a moderate increase in liver cancer risk in obese postmenopausal women in the United States. Larger study is needed to confirm our observation on effect modification by adiposity status.

Sleep and circadian disruption and incident breast cancer risk: An evidence-based and theoretical review

Opportunities for restorative sleep and optimal sleep-wake schedules are becoming luxuries in industrialized cultures, yet accumulating research has revealed multiple adverse health effects of disruptions in sleep and circadian rhythms, including increased risk of breast cancer. The literature on breast cancer risk has focused largely on adverse effects of night shift work and exposure to light at night (LAN), without considering potential effects of associated sleep disruptions. As it stands, studies on breast cancer risk have not considered the impact of both sleep and circadian disruption, and the possible interaction of the two through bidirectional pathways, on breast cancer risk in the population at large. We review and synthesize this literature, including: 1) studies of circadian disruption and incident breast cancer; 2) evidence for bidirectional interactions between sleep and circadian systems; 3) studies of sleep and incident breast cancer; and 4) potential mechanistic pathways by which interrelated sleep and circadian disruption may contribute to the etiology of breast cancer.

Cancer Prevention During Early Adulthood: Highlights From a Meeting of Experts

Using a life course approach, the Centers for Disease Control and Prevention's Division of Cancer Prevention and Control and the National Association of Chronic Disease Directors co-hosted a 2-day meeting with 15 multidisciplinary experts to consider evidence linking factors in early adulthood to subsequent cancer risk and strategies for putting that evidence into practice to reduce cancer incidence. This paper provides an overview of key themes from those meeting discussions, drawing attention to the influence that early adulthood can have on lifetime cancer risk and potential strategies for intervention during this phase of life. A number of social, behavioral, and environmental factors during early adulthood influence cancer risk, including dietary patterns, physical inactivity, medical conditions (e.g., obesity, diabetes, viral infections), circadian rhythm disruption, chronic stress, and targeted marketing of cancer-causing products (e.g., tobacco, alcohol). Suggestions for translating research into practice are framed in the context of the four strategic directions of the National Prevention Strategy: building healthy and safe community environments; expanding quality preventive services in clinical and community settings; empowering people to make healthy choices; and eliminating health disparities. Promising strategies for prevention among young adults include collaborating with a variety of community sectors as well as mobilizing young adults to serve as advocates for change. Young adults are a heterogeneous demographic group, and targeted efforts are needed to address the unique needs of population subgroups that are often underserved and under-represented in research studies.

Sleep Duration across the Adult Lifecourse and Risk of Lung Cancer Mortality: A Cohort Study in Xuanwei, China

Sufficient sleep duration is crucial for maintaining normal physiological function and has been linked to cancer risk; however, its contribution to lung cancer mortality is unclear. Therefore, we evaluated the relationship between average sleep duration in various age-periods across the adult lifecourse, and risk of lung cancer mortality in Xuanwei, China. An ambidirectional cohort study was conducted in 42,422 farmers from Xuanwei, China. Participants or their surrogates were interviewed in 1992 to assess average sleep hours in the age periods of 21-30, 31-40, 41-50, 51-60, 61-70, and ≥71 years, which were categorized as ≤7, 8 (reference), 9, and ≥10 hours/day. Vital status was followed until 2011. Sex-specific Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for lung cancer mortality in 1994-2011, adjusted for demographic, anthropometric, medical, and household characteristics. J-shaped relationships were found between average sleep duration and lung cancer mortality. The patterns were consistent across sex, age periods, and fuel usage. Compared with sleeping 8 hours/day on average, ≤7 hours/day was associated with significantly increased HRs ranging from 1.39 to 1.58 in ages ≥41 years in men, and 1.29 to 2.47 in ages ≥51 years in women. Furthermore, sleeping ≥10 hours/day was associated with significantly increased HRs ranging from 2.44 to 3.27 in ages ≥41 year in men, and 1.31 to 2.45 in ages ≤60 years in women. Greater and less than 8 hours/day of sleep in various age-periods may be associated with elevated risk of lung cancer mortality in Xuanwei, China. Cancer Prev Res; 10(6); 327-35. ©2017 AACR.

The National Veteran Sleep Disorder Study: Descriptive Epidemiology and Secular Trends, 2000-2010

STUDY OBJECTIVES

A large proportion of individuals affected by sleep disorders are untreated and susceptible to accidents, injuries, long-term sequelae (e.g., risk of cardiovascular disease, cancer, psychiatric disorders), and increased mortality risk. Few studies have examined the scope and magnitude of sleep disorder diagnoses in the United States (US) or factors influencing them. Veterans are particularly vulnerable to factors that elicit or exacerbate sleep disorders.

METHODS

This serial cross-sectional study characterized secular trends in diagnosed sleep disorders among veterans seeking care in US Veterans Health Administration facilities over an eleven-year span (FY2000-2010, n = 9,786,778). Electronic medical records from the national Veterans Administration Informatics and Computing Infrastructure database were accessed. Cases were defined using diagnostic codes specified by the American Academy of Sleep Medicine. Age-adjusted annual prevalence was summarized by sex, race, combat exposure, body mass index, and comorbid diagnoses (cardiovascular disease, cancer, mental disorders).

RESULTS

Sleep apnea (47%) and insomnia (26%) were the most common diagnoses among patients with any sleep disorder. There was a six-fold relative increase in total sleep disorder prevalence over the study period. Posttraumatic stress disorder, which tripled over the same time period, was associated with the highest prevalence of sleep disorders (16%) among the comorbid conditions evaluated.

CONCLUSIONS

The results indicate a growing need for integration of sleep disorder management with patient care and health care planning among US veterans.

COMMENTARY

A commentary on this article appears in this issue on page 1331.

Nighttime sleep duration, 24-hour sleep duration and risk of all-cause mortality among adults: a meta-analysis of prospective cohort studies

A dose-response meta-analysis was conducted to summarize evidence from prospective cohort studies about the association of nighttime sleep duration and 24-hour sleep duration with risk of all-cause mortality among adults. Pertinent studies were identified by a search of Embase and PubMed databases to March 2015. A two-stage random-effects dose-response meta-analysis was used to combine study-specific relative risks and 95% confidence intervals [RRs (95% CIs)]. Thirty-five articles were included. Compared with 7 hours/day, the RRs (95% CIs) of all-cause mortality were 1.07 (1.03-1.13), 1.04 (1.01-1.07), 1.01 (1.00-1.02), 1.07 (1.06-1.09), 1.21 (1.18-1.24), 1.37 (1.32-1.42) and 1.55 (1.47-1.63) for 4, 5, 6, 8, 9, 10 and 11 hours/day of nighttime sleep, respectively (146,830 death cases among 1,526,609 participants), and the risks were 1.09 (1.04-1.14), 1.05 (1.02-1.09), 1.02 (1.00-1.03), 1.08 (1.05-1.10), 1.27 (1.20-1.36), 1.53 (1.38-1.70) and 1.84 (1.59-2.13) for 4, 5, 6, 8, 9, 10 and 11 hours/day of 24-hour sleep, respectively (101,641 death cases among 903,727 participants). The above relationships were also found in subjects without cardiovascular diseases and cancer at baseline, and other covariates did not influence the relationships substantially. The results suggested that 7 hours/day of sleep duration should be recommended to prevent premature death among adults.

Sleep Duration and Disruption and Prostate Cancer Risk: a 23-Year Prospective Study

BACKGROUND

Sleep deficiency is a major public health problem. There are limited human data on whether sleep duration or disruption are risk factors for prostate cancer.

METHODS

We prospectively followed 32,141 men in the Health Professionals Follow-Up Study who reported their typical sleep duration in 1987, 2000, and 2008. We identified 4,261 incident prostate cancer cases, including 563 lethal cases through 2010. Sleep disruption was assessed in 2004 among 19,639 men, with 930 prostate cancer cases (50 lethal) identified from 2004 to 2010. Cox proportional hazards models were used to evaluate the association between sleep insufficiency and risk of overall and lethal prostate cancer.

RESULTS

In 1987, 2% of men reported sleeping ≤5 hours per night. We found no association between habitual sleep duration or change in sleep duration with the risk of advanced or lethal prostate cancer. We also found no association between waking up during the night, difficulty falling asleep, or waking up too early, and risk of prostate cancer. In 2004, 6% of men reported never feeling rested when they woke up; these men had an increased risk of developing lethal prostate cancer compared with those who reported always feeling rested when they woke up (RR, 3.05; 95% CI, 1.15-8.10).

CONCLUSIONS

We found no consistent association between self-reported sleep duration or sleep disruption and any of our prostate cancer outcomes.

IMPACT

We did not find support for a consistent association between self-reported sleep and risk of advanced or lethal prostate cancer in this large cohort of men.

Sleep duration and cancer risk in women

PURPOSE

The objective was to conduct an analysis of sleep duration and risk of selected site-specific and groups of cancer among a large prospective cohort of California women.

METHODS

The study population was comprised of 101,609 adult females participating in the California Teachers Study. All sites of invasive cancer prospectively diagnosed from baseline (1995-1996) through 2011 were identified through linkage to the California Cancer Registry (n = 12,322). Site-specific analyses focused on the following cancers: breast (n = 5,053), colorectal (n = 983), lung (n = 820), melanoma (n = 749), and endometrial (n = 957). Additionally, we evaluated a group of estrogen-mediated cancers consisting of breast, endometrial, and ovarian cancer (n = 6,458). Sleep duration was based on self-report of average time sleeping in the year prior to baseline. Cox proportional hazard models were used to calculate adjusted hazard ratios and 95 % confidence intervals (HRs, 95 % CI).

RESULTS

Point estimates for all sites and site-specific cancers generally were near or below one for short sleepers (<6 h/night) and above one for long sleepers (10+ h/night); confidence intervals, however, were wide and included unity. Compared to average sleepers (7-9 h/night), long sleepers had an increased risk of the group of estrogen-mediated cancers (HR 1.22, 95 % CI 0.97-1.54, p (trend) = 0.04).

CONCLUSIONS

These analyses suggest that longer sleep may be associated with increased risks of estrogen-mediated cancers. Further studies with more refined measures of sleep duration and quality are warranted.

Obstructive sleep apnea and cancer: Epidemiologic links and theoretical biological constructs

Sleep disorders have emerged as highly prevalent conditions in the last 50-75 y. Along with improved understanding of such disorders, the realization that perturbations in sleep architecture and continuity may initiate, exacerbate or modulate the phenotypic expression of multiple diseases including cancer has gained increased attention. Furthermore, the intermittent hypoxia that is attendant to sleep disordered breathing, has recently been implicated in increased incidence and more adverse prognosis of cancer. The unifying conceptual framework linking these associations proposes that increased sympathetic activity and/or alterations in immune function, particularly affecting innate immune cellular populations, underlie the deleterious effects of sleep disorders on tumor biology. In this review, the epidemiological evidence linking disrupted sleep and intermittent hypoxia to oncological outcomes, and the potential biological underpinnings of such associations as illustrated by experimental murine models will be critically appraised. The overarching conclusion appears supportive in the formulation of an hypothetical framework, in which fragmented sleep and intermittent hypoxia may promote changes in multiple signalosomes and transcription factors that can not only initiate malignant transformation, but will also alter the tumor microenvironment, disrupt immunosurveillance, and thus hasten tumor proliferation and increase local and metastatic invasion. Future bench-based experimental studies as well as carefully conducted and controlled clinical epidemiological studies appear justified for further exploration of these hypotheses.

Association between sleep-disordered breathing, obstructive sleep apnea, and cancer incidence: a systematic review and meta-analysis

OBJECTIVE/BACKGROUND

Via this systematic review and meta-analysis, we assessed the associatio between sleep-disordered breathing (SDB)/obstructive sleep apnea (OSA) and cancer incidence.

METHOD

Medline, Embase, Cochrane Central, and electronic databases were searched for relevant studies in any language. Studies were included based on the following criteria: (1) those on patients with SDB/OSA, (2) those reporting cancer incidence rates specific to patients with SDB/OSA, and (3) those defining SDB/OSA using sleep-study-based objective measures. The quality of the included studies was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOQA).

RESULTS

Of the 8766 retrieved citations, five studies that defined SDB/OSA using the apnea-hypopnea index (AHI) or the respiratory disturbance index (RDI) totaling 34,848 patients with SDB and 77,380 patients without SDB were pooled into a meta-analysis. All five studies were of good quality (NOQA ≥ 6). A total of 574 (1.6%) and 290 (0.37%) incident cancers were reported in patients with and without SDB, respectively. In the unadjusted analysis, patients with SDB/OSA were at an increased risk of incident cancer (relative risk [RR]: 1.53, 95% confidence interval [CI]: 1.31-1.79, P <0.001, I(2): 0, five included studies). When adjusted for traditional cancer risk factors, the association between SDB/OSA and cancer incidence, although attenuated (RR: 1.40, 95% CI: 1.01-1.95, P = 0.04, I(2): 60%, five included studies), remains significant.

CONCLUSIONS

SDB/OSA may increase the risk of incident cancer. Inferring an independent association is not possible from our analysis considering the retrospective cohort design of the included studies and high inter-study heterogeneity. An individual patient data meta-analysis would help validate our findings.

Reduced NADPH oxidase type 2 activity mediates sleep fragmentation-induced effects on TC1 tumors in mice

The molecular mechanisms underlying how sleep fragmentation (SF) influences cancer growth and progression remain largely elusive. Here, we present evidence that SF reduced ROS production by downregulating gp91^phox expression and activity in TC1 cell tumor associated macrophages (TAMs), while genetic ablation of phagocytic Nox2 activity increased tumor cell proliferation, motility, invasion, and extravasation in vitro. Importantly, the in vivo studies using immunocompetent syngeneic murine tumor models suggested that Nox2 deficiency mimics SF-induced TAMs infiltration and subsequent tumor growth and invasion. Taken together, these studies reveal that perturbed sleep could adversely affect innate immunity within the tumor by altering Nox2 expression and activity, and indicate that selective potentiation of Nox2 activity may present a novel therapeutic strategy in the treatment of cancer.

Sleep duration affects risk for ulcerative colitis: a prospective cohort study

BACKGROUND & AIMS

Sleep deprivation is associated with production of inflammatory cytokines. Disturbed sleep quality has been associated with increased risk of disease flare in patients with Crohn's disease (CD) or ulcerative colitis (UC). However, the association between sleep and risk of incident CD and UC has not been previously examined.

METHODS

We conducted a prospective study of women who were enrolled in the Nurses' Health Study (NHS) I since 1976 and NHS II since 1989 and followed through detailed biennial questionnaires with >90% follow-up. We examined the association of sleep duration reported in 1986 in NHS I and 2001 in NHS II with incident CD and UC, diagnosed through 2010, in NHS I and 2009 in NHS II. Cox proportional hazards models adjusting for potential confounders were used to calculate hazard ratios and 95% confidence intervals (CIs).

RESULTS

Among 151,871 women, we confirmed 191 cases of CD (incidence, 8/100,000 person-years) and 230 cases of UC (incidence, 10/100,000 person-years) over 2,292,849 person-years. Compared with women with reported usual sleep durations of 7-8 h/day (incidence, 8/100,000 person-years), women with reported sleep duration <6 h/day (11/100,000 person-years) or >9 h/day (20/100,000 person-years) had a higher incidence of UC (P < .05). The multivariate hazard ratios for UC were 1.51 (95% CI, 1.10-2.09) for sleep durations <6 h/day and 2.05 (95% CI, 1.44-2.92) for sleep durations >9 h/day, compared with sleep durations of 7-8 h/day. In contrast, sleep duration did not modify risk of CD. Duration of rotating night shift work was not associated with CD or UC.

CONCLUSIONS

On the basis of data from the NHS I and II, less than 6 hours sleep/day and more than 9 hours sleep/day are each associated with an increased risk of UC. Further studies are needed to evaluate sleep as a modifiable risk factor in the pathogenesis and progression of IBD.

Sleep duration and incidence of lung cancer in ageing men

BACKGROUND

Previous studies have suggested an association between sleep duration and cancer. However, the information on sleep duration regard to risk of lung cancer is scanty.

METHODS

Analysed data comprised prospective population-based cohort of 2586 men (aged 42-60 years) from Eastern Finland. Baseline survey and clinical examinations took place 1984-1989, and diagnosed lung cancers were obtained until the end of 2011 through linkage with the Finnish Cancer Registry. Self-reported sleep was categorized as ≤6.5 h, 7-7.5 h, and ≥8 h. Subjects with prior history of cancer or psychotropic medication (hypnotics or sedatives) were excluded from the analyses. Cox proportional hazards models with adjustments for possible confounders were used to examine the association.

RESULTS

Significant association between sleep duration and increased lung cancer risk was observed after adjustments for age, examination years, cumulative smoking history, family cancer history and Human Population Laboratory Depression scale scores (HR 2.12, 95% CI 1.17-3.85 for ≤6.5 h sleep, and HR 1.88, 95% CI 1.09-3.22 for ≥8 h sleep). Associations were even stronger among current smokers (HR 2.23, 95% CI 1.14-4.34 for ≤6.5 h sleep, and HR 2.09, 95% CI 1.14-3.81 for ≥8 h sleep). After further adjustments for alcohol consumption, physical activity, body mass index, marital status, education years, night work, employment status, asthma and chronic bronchitis, the association remained significant both in the whole study population and among smokers. When cumulative smoking history was replaced by current smoking in the adjustments, the increased risk was limited to those who slept<6.5 h.

CONCLUSIONS

Sleep duration of less than 7-7.5 hours or more than 7-7.5 hours associates with increased lung cancer risk. The physiological factors underlying the association are complex, and they may relate to melatonin excretion patterns, low-grade inflammation in cancer development process or disruptions in circadian rhythmicity.