Daytime napping and the incidence of Parkinson's disease: a prospective cohort study with Mendelian randomization.

BACKGROUND: The causal relationship between daytime napping and the risk of Parkinson's disease (PD) remains unclear, with prospective studies providing limited evidence. This study investigated the association between daytime napping frequency and duration and PD incidence and explored the causality relationship between this association by conducting Mendelian randomization (MR) analysis. METHODS: This prospective cohort study included 393,302 participants, and accelerometer-measured daytime napping data were available only for 78,141 individuals. Cox proportional hazards regression was used to estimate the association between the daytime napping frequency and duration and the PD risk. The role of the systemic immune-inflammation index (SII) in the association between daytime napping frequency and PD risk was assessed through mediation analyses. Moreover, the causal association between the daytime napping frequency and the PD risk was preliminarily explored by conducting two-sample MR analyses. RESULTS: The median follow-up duration was 12.18 years. The participants who reported napping sometimes or usually exhibited a significantly higher PD risk than those who never/rarely napped during the day [sometimes: hazard ratio (HR), 1.13; 95% confidence interval (CI), 1.03-1.23; usually: HR, 1.33; 95% CI, 1.14-1.55], and SII played a mediating role in this association. However, the MR analyses did not indicate that the daytime napping frequency and PD risk were significantly associated. The participants napping for over 1 h exhibited a significantly elevated PD risk (HR, 1.54; 95% CI, 1.11-2.16). Moreover, no significant interaction was identified between napping frequency or duration and genetic susceptibility to PD (P for interaction > 0.05). CONCLUSIONS: In this study, increased daytime napping frequency and duration were associated with an increased PD risk, but no causal relationship was observed between napping frequency and PD risk in the MR analysis. Larger GWAS-based cohort studies and MR studies are warranted to explore potential causal relationships.

Daytime napping and the risk of gastric cancer: the JACC Study.

BACKGROUND: Gastric cancer is a major cause of morbidity and mortality in Japan and worldwide. Emerging literature has suggested unfavorable health outcomes associated with daytime napping. Herein, we aimed to investigate the association between daytime napping and the risk of gastric cancer among Japanese people. METHODS: This prospective cohort study included 49,037 participants, aged 40-79 years, from the Japan Collaborative Cohort Study (JACC Study). Participants with positive cancer history and those who reported night or rotational shift work were excluded. Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) of incident gastric cancer among daytime nappers. RESULTS: Within 650,040 person-years (median = 13.7 years) of follow-up, 1,164 participants developed gastric cancer. Daytime napping was associated with the increased risk of gastric cancer in the multivariable-adjusted model: HR (95% CI) = 1.14 (1.01, 1.29). The excess risk did not significantly differ across sexes, age groups (<65 and ≥65 years), and employment status (employed and unemployed) (p-interactions > 0.40). However, sleep duration modified this effect: HRs (95% CIs) = 1.66 (1.23, 2.23) in sleep duration ≤6 h/night versus 1.06 (0.93, 1.21) in sleep duration >6 h/night (p-interaction = 0.006). CONCLUSION: Daytime napping was associated with increased gastric cancer risk, especially among those who reported short sleep duration.

Effects of Testosterone in Mediating the Relationship Between Daytime Napping and Osteoporosis in European Populations: A Mendelian Randomization Study.

We aimed to explore the causal effect of daytime napping on the risk of osteoporosis and the mediation role of testosterone in explaining this relationship. Summary data for Mendelian randomization (MR) analysis were obtained from the IEU OpenGWAS database. Univariable MR(UVMR) analysis and multiple sensitivity analyses were applied to explore the casual relationship between daytime napping and bone mineral density (BMD)/osteoporosis. We also conducted multivariable Mendelian randomization (MVMR) analysis to evaluate the correlation between testosterone-associated single-nucleotide variations and BMD/osteoporosis. Then, mediation analysis was performed to explore whether the association between daytime napping and BMD/osteoporosis was mediated via testosterone. Genetically predicted daytime napping was significantly associated with femoral neck BMD (ß [95% CI]: 0.2573 [0.0487, 0.4660]; P = 0.0156), lumbar spine BMD (ß [95% CI]: 0.2526 [0.0211, 0.4840]; P = 0.0324), and osteoporosis (OR [95% CI]: 0.5063 [0.2578, 0.9942]; P = 0.0481). ß and 95%CIs indicate the standard deviation (SD) unit of BMD increase per category increase in daytime napping. OR and 95%CIs represent the change in the odds ratio of osteoporosis per category increase in daytime napping. We observed a potentially causal effect of more frequent daytime napping on higher BMD and a lower risk of osteoporosis. Daytime napping was causally associated with a higher level of bioavailable testosterone (ß [95% CI]: 0.1397 [0.0619, 0.2175]; P = 0.0004). ß and 95%CIs represent the change in the SD of testosterone per category increase in daytime napping. Furthermore, the causal effects of daytime napping on BMD/osteoporosis were partly mediated by bioavailable testosterone. Daytime napping can efficiently increase BMD and reduce the risk of osteoporosis, and testosterone plays a key mediating role in this process.

Napping and Obesity in Adults - What do we Know?

PURPOSE OF REVIEW: To review the evidence on the relationship between daytime napping and obesity. RECENT FINDINGS: There is concern that napping may be harmful to metabolic health. Prospective studies have shown long time daytime napping (> 1 h) is associated with increased diabetes risk which may be partly associated with obesity. Evidence from numerous cross-sectional studies and meta-analyses of cross-sectional studies have shown that long time napping (> 1 h) but not short time napping is associated with increased risk of obesity, and this is seen worldwide. Inference regarding the nature of association from cross-sectional studies is limited; it is suggested the association is bidirectional. Prospective studies on the association between daytime napping and obesity are few and results unclear. Large longitudinal studies integrating daytime napping duration and night-time sleep behaviour and detailed information on lifestyle influences is needed to help elucidate further the associations of long time napping with obesity.

Long daytime napping: A silent danger for hypertensive individuals.

BACKGROUND AND PURPOSE: Hypertension significantly contributes to stroke. Previous research has indicated a connection between daytime napping and stroke. Research on the connection between daytime napping duration and first stroke in hypertensive individuals is lacking nevertheless. METHODS: This research, which ran from 24 August 2013 to 31 December 2022, recruited 11,252 individuals with hypertension and without a history of stroke from the China Stroke Primary Prevention Trial. To determine the relationship between daytime napping duration and stroke onset in hypertensive individuals, we conducted analyses for threshold effects, multivariate-adjusted Cox proportional hazard regression models, and Kaplan-Meier survival curves. RESULTS: The duration of daytime napping (<75 min) was positively correlated with stroke risk; beyond 75 min, the risk did not increase further. When compared to hypertensive individuals who napped for 1-30 min, daytime napping 31-60 min (hazard ratio [HR] = 1.27, 95% confidence interval [CI] = 1.06-1.53) and >60 min (HR = 1.37, 95% CI = 1.14-1.65) were substantially related with a greater risk of first stroke. Additionally, this correlation was absent in cases of hemorrhagic stroke, but present in cases of ischemic stroke, specifically for hypertensive individuals who napped for 31-60 min or >60 min (p < 0.05). Kaplan-Meier survival curves displayed that hypertensive individuals who extended daytime napping had an elevated incidence of stroke. CONCLUSIONS: Hypertensive individuals who take longer daytime naps (>30 min) are at an elevated risk of stroke onset, particularly ischemic stroke, irrespective of other factors.

Prevalence and associated factors of napping among older adults in the Philippines.

BACKGROUND: The aim of the study is to estimate the prevalence and associated factors of insomnia among older adults in the Philippines. METHODS: In all, 5206 cross-sectional nationally representative data from older adults (≥ 60 years) of the 2018 Longitudinal Study on Ageing and Health in the Philippines (LSAHP) was analysed. Napping frequency and duration were assessed by self-report. RESULTS: The prevalence of regular nappers was 35.7%, low or moderate napping (1-59 min) was 10.5% and long napping (≥ 60 min) duration was 25.2%. In the final adjusted model, older age was not significantly associated with low or moderate napping duration but older age was positively associated with long napping duration. High wealth status, physical activity and late insomnia were positively associated with low or moderate napping duration. High wealth status, urban residence, daily activity limitations, and physical activity were positively associated, and currently working status, poor self-rated health status and current alcohol use were negatively associated with long napping duration. CONCLUSION: One in four older adults reported long napping duration. Sociodemographic, health status and behaviour and sleep parameters were associated with low or moderate and/or long napping duration.

Causal associations between leisure sedentary behaviors and sleep status with frailty: insight from Mendelian randomization study.

BACKGROUND: Observational studies have suggested that sedentary behaviors and sleep status are associated with frailty. However, it remains unclear whether these associations are causal. METHODS: Using summary statistics from genome-wide association studies, we evaluated the causal effect of modifiable risk factors, including leisure sedentary behaviors and sleep status on the frailty index (FI) using two-sample univariable and multivariable Mendelian randomization (MR) analyses. Genetic correlations were tested between the correlated traits. RESULTS: We identified potential causal associations between the time spent watching television (ß = 0.26, 95% confidence interval [CI]: 0.21-0.31, P = 3.98e-25), sleep duration (ß = -0.18, 95%CI: -0.26, -0.10; P = 6.04e-06), and daytime napping (ß = 0.29, 95%CI: 0.18-0.41, P = 2.68e-07) and the FI based on the inverse-variance-weighted method. The estimates were consistent across robust and multivariate MR analyses. Linkage disequilibrium score regression detected a genetic correlation between the time spent watching television (Rg = 0.43, P = 6.46e-48), sleep duration (Rg = -0.20, P = 5.29e-10), and daytime napping (Rg = 0.25, P = 3.34e-21) and the FI. CONCLUSIONS: Genetic predispositions to time spent watching television and daytime napping were positively associated with the FI, while sleep duration was negatively associated with the FI. Our findings offer key insights into factors influencing biological aging and suggest areas for interventions to promote healthy aging and slow down the aging process.

Association between sleep patterns and galectin-3 in a Chinese community population.

BACKGROUND: Irregular sleep patterns have been associated with inflammation. Galectin-3, a novel biomarker, plays an important role in inflammation. We investigated the relationship between sleep patterns and galectin-3 in a Chinese population. METHODS: A total of 1,058 participants from the Shenzhen-Hong Kong United Network on Cardiovascular Disease study were included in the analysis. Age and sex-adjusted linear regression models were employed to investigate the relationship between galectin-3 level and traditional metabolic biomarkers. Logistic regression models were used to estimate the association among sleep disturbance, nighttime sleep duration, and daytime napping duration and elevated galectin-3, with elevated galectin-3 defined as galectin-3 level > 65.1 ng/ml. RESULTS: Of study participants, the mean age was 45.3 years and 54.3% were women. Waist circumference, natural logarithm (ln)-transformed triglyceride, and ln-transformed high sensitivity C-reactive protein were positively associated with galectin-3 level (age and sex-adjusted standardized ß [95% confidence interval (CI)], 0.12 [0.04, 0.21], 0.11 [0.05, 0.17], and 0.08 [0.02, 0.14], respectively). Sleep disturbance was associated with elevated galectin-3 (odds ratio [95% CI], 1.68 [1.05, 2.68], compared to those without sleep disturbance) after adjusting for traditional metabolic biomarkers. No interaction was observed between galectin-3 and age, sex, obesity, hypertension, and diabetes on sleep disturbance. No association was found between nighttime sleep duration or daytime napping duration and elevated galectin-3. CONCLUSIONS: Our study provides evidence of a significant association between sleep disturbance and elevated galectin-3 level, independent of traditional metabolic biomarkers. Screening and interventions on galectin-3 could assist in preventing sleep disturbance-induced inflammatory disease.

Association of night-time sleep and daytime napping with painful temporomandibular disorder.

BACKGROUND: Painful temporomandibular disorder (TMD) is the common cause of chronic oro-facial pain, which may interfere with sleep. Previous studies have documented an association between sleep and TMD. OBJECTIVES: This study aimed to further explore the association of night-time sleep and daytime napping with painful TMD. METHODS: A total of 419 patients (aged 31.88 ± 11.54 years with women forming 85.4%) from a TMD/Orofacial Pain center were enrolled. Patients' sleep conditions were evaluated with the Pittsburgh Sleep Quality Index (PSQI) questionnaire, and information on night-time sleep duration, napping duration and napping frequency was interviewed. TMD was diagnosed according to the Diagnostic Criteria for TMD protocol and stratified into myalgia (muscle pain), arthralgia (joint pain) and combined (muscle and joint pain) subgroups. The severity of TMD was measured with the Fonseca Anamnestic Index (FAI) questionnaire. Restricted cubic spline (RCS) regression models were established to explore relationships between sleep and painful TMD subgroups. RESULTS: Patients with poor sleep quality (PSQI≥6) had higher FAI scores (median 60, p < .001) and higher proportions of painful TMDs. The myalgia subgroup had higher PSQI scores (median 8, p < .001) than the arthralgia subgroup. The RCS models indicated a non-linear relationship between night-time sleep duration and myalgia (p < .001), which was not observed in arthralgia. However, there were no significant findings concerning napping and painful TMD subgroups. CONCLUSION: This study found that the association between sleep and TMD is mainly related to painful TMD conditions, which are associated with night-time sleep duration.

Association between nocturnal sleep duration and midday napping and the incidence of sarcopenia in middle-aged and older adults: a 4-year longitudinal study.

BACKGROUND: Identifying treatment targets for sarcopenia is a public health concern. This study aimed to examine the association of nocturnal sleep duration and midday napping with the presence of sarcopenia in middle-aged and older adults, utilizing data from the China Health and Retirement Longitudinal Study in 2011 and 2015. METHODS: A sum of 7,926 individuals (≥40 years) took part in this study. Sarcopenia was diagnosed according to the Asian Working Group for Sarcopenia. A self-reported questionnaire was used to collect data on nocturnal sleep duration and midday napping. Nocturnal sleep duration was categorized into three groups: short sleepers (<6 h), normal sleepers (6-8 h), and long sleepers (>8 h). Midday napping was coded as a dichotomous outcome (yes/no). RESULTS: The incidence of sarcopenia was 5.3% during the 4-year follow-up. Short sleep duration (<6 h) was substantially linked to an increased incidence of sarcopenia (OR: 1.50, 95% CI: 1.21-1.87) as compared to nocturnal sleep length (6-8 h). Adults with midday napping had a lower risk of developing sarcopenia than non-nappers (OR: 0.78, 95% CI: 0.63-0.95). We further found that short sleepers with midday napping did not have a significantly higher risk of subsequent diagnosis of sarcopenia compared to normal sleepers without midday napping. CONCLUSION: These findings imply that short sleep duration in middle-aged and older persons is related to an increased incidence of sarcopenia. However, the adverse effect of short sleep duration on sarcopenia can be compensated by midday napping.

Association of habitual sleep duration and its trajectory with the risk of cancer according to sex and body mass index in a population-based cohort.

BACKGROUND: The relationship between sleep duration and cancer in China remains inconclusive. The authors investigated the association between sleep duration and cancer from both static and dynamic perspectives. METHODS: This study was based on the China Health and Retirement Longitudinal Study. We first tested the hazard ratios (HRs) with 95% confidence intervals (CIs) between baseline sleep duration and incident cancer using Cox proportional hazards regression analysis. Sleep duration trajectories from 2011 to 2015 were identified using group-based trajectory modeling to examine the subsequent risk of incident cancer from 2015 to 2018 using Cox proportional hazards regression model. RESULTS: The risk of incident cancer increased by 69% (HR, 1.69; 95% CI, 1.19-2.39) in individuals who slept for <7 h per day (vs. 7 to ≤8 h), 41% (HR, 1.41; 95% CI, 1.01-1.95) in those who slept for <6 h per night (vs. 6 to ≤8 h), and 60% (HR, 1.60; 95% CI, 1.01-2.55) in those who did not take any naps during the day (vs. >60 min). Stratified by sex and body mass index, the risk of cancer was evident among women with night sleep of <6 h (vs. 6-8 h). However, the duration of <7 h of total sleep among men and overweight individuals was associated with cancer risk. Moreover, individuals with a short night sleep duration but no napping had a higher risk of cancer. Furthermore, cancer risk was only observed in individuals with short stable trajectory of night sleep (HR, 2.01; 95% CI, 1.07-3.80) and among women with short stable trajectory of total sleep (HR, 2.26; 95% CI, 1.13-4.52). CONCLUSIONS: Cancer incidence risk was observed in participants with sleep duration of <7 h and among women with short stable sleep trajectory. Short nights and total sleep duration were both associated with a high risk of incident cancer, but varied by sex. Interestingly, cancer risk was restricted to women with short stable sleep trajectory. PLAIN LANGUAGE SUMMARY: This study showed that short nights and total sleep duration were associated with a high risk of cancer incidence in middle-aged and elderly Chinese population, with implications for early effective cancer prevention. Habitual sleep is a modifiable and dynamic lifestyle behavior, and long-term short sleep trajectories among women can predict cancer outcomes. Future studies should examine the association between the trajectory of sleep parameters based on objective measures and specific cancer types.

Association of Self-Reported Nighttime Sleep Duration with Chronic Kidney Disease: China Health and Retirement Longitudinal Study.

INTRODUCTION: The cohort study aimed to assess the association of nighttime sleep duration and the change in nighttime sleep duration with chronic kidney disease (CKD) and whether the association between nighttime sleep duration and CKD differed by daytime napping. METHODS: This study included 11,677 individuals from the China Health and Retirement Longitudinal Study (CHARLS) and used data from the 2011 baseline survey and four follow-up waves. Nighttime sleep duration was divided into three groups: short (<7 h per night), optimal (7-9 h), and long nighttime sleep duration (>9 h). Daytime napping was divided into two groups: no nap and with a nap. We used Cox proportional hazards model to examine the effect of nighttime sleep duration at baseline and change in nighttime sleep duration on incident CKD and a joint effect of nighttime sleep duration and nap time on onset CKD. RESULTS: With a follow-up of 7 years, the incidence of CKD among those with short, optimal, and long nighttime sleep duration was 9.89, 6.75, and 9.05 per 1,000 person-years, respectively. Compared to individuals with optimal nighttime sleep duration, short nighttime sleepers had a 44% higher risk of onset CKD (hazard ratio [HR]: 1.44, 95% confidence interval [CI]: 1.21-1.72). Compared to participants with persistent optimal nighttime sleep duration, those with persistent short or long nighttime sleep duration had an increased risk of incident CKD (HR: 1.44, 95% CI: 1.15-1.80). We found a lower incidence of CKD in participants with short nighttime sleep duration and a nap (HR: 0.74, 95% CI: 0.60-0.93), compared to those with short nighttime sleep duration and no nap. CONCLUSION: Short nighttime sleep duration and persistent long or short nighttime sleep duration were associated with a higher risk of onset CKD. Keeping persistent optimal nighttime sleep duration may help reduce CKD risk later in life. Daytime napping may be protective against CKD incidence.

Sleep Duration and Daytime Napping and Risk of Type 2 Diabetes Among Japanese Men and Women: The Japan Collaborative Cohort Study for Evaluation of Cancer Risk.

BACKGROUND: Little is known about the impacts of sleep duration and daytime napping on the risk of type 2 diabetes mellitus (T2DM). METHODS: In this study, 20,318 participants (7,597 men, 12,721 women) aged 40-79 years without a history of T2DM, stroke, coronary heart disease, or cancer at baseline (1988-1990), completed the baseline survey and the 5-year follow-up questionnaires, which included average sleep duration, napping habits, and self-reports of physician-diagnosed diabetes. The multivariable odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a logistic regression model. RESULTS: During the 5-year follow-up, 531 new cases of T2DM (266 men and 265 women) were documented. Sleep duration ≥10 hours was associated with higher risk of T2DM compared to sleep duration of 7 hours (OR 1.99; 95% CI, 1.28-3.08). The excess risk was observed for both sexes and primarily found among the non-overweight; the multivariable ORs of sleeping ≥10 hours compared to 7 hours were 2.05 (95% CI, 1.26-3.35) for the non-overweight (BMI <25 kg/m2) and 1.38 (95% CI, 0.49-3.83) for the overweight (BMI ≥25 kg/m2). The respective ORs of nappers versus non-nappers were 1.30 (95% CI, 1.03-1.63) and 0.92 (95% CI, 0.65-1.29). Among the non-overweight, nappers who slept ≥10 hours had the highest risk of T2DM (OR 2.84; 95% CI, 1.57-5.14), non-nappers who slept ≥10 hours (OR 2.27; 95% CI, 1.27-4.06), and nappers who slept <10 hours (OR 1.30; 95% CI, 1.03-1.64), compared with non-nappers who slept <10 hours. CONCLUSION: Long sleep duration was associated with the risk of T2DM in both sexes, which was confined to the non-overweight.

A Mendelian randomization study revealed a causal link between napping and deep vein thrombosis (DVT).

BACKGROUND: Numerous individuals opt for napping to achieve adequate rest, and several studies have linked napping to various health conditions. Consequently, we aimed to investigate the potential effect of napping on the development of deep vein thrombosis (DVT). METHODS: We used the publicly available summary statistics data sets of genome-wide association studies (GWAS) meta-analyses for napping in individuals included in the UK Biobank as the exposure and a GWAS for DVT from the individuals included in the FinnGen Biobank as the outcome. The two-sample MR research approach was utilized to explore the causative link between napping and DVT. Single nucleotide polymorphisms (SNPs) data strongly related to napping were found and used as instrumental factors. Inverse variance weighting (IVW), weighted median and MR-Egger regression, and weighted mode approaches were four statistical techniques. RESULTS: There were 86 SNPs in all that were discovered to be strongly related to napping (P < 5 × 10-8, linkage disequilibrium r2 < 0.1). Consistent association between napping and DVT (IVW: odds ratio (OR) 0.508, 95% confidence interval (CI) 0.280-0.921; MR-Egger regression: OR 0.988, 95% CI 0.118-8.303; weighted median estimates: OR 0.419, 95% CI 0.181-0.974; weighted mode: OR 0.442, 95% CI 0.080-2.427) suggested that napping correlated with decreased risk of DVT. There was no evidence that genetic pleiotropy affected the link between napping and DVT (MR-Egger intercept - 6.7 × 10-3; P = 0.525). CONCLUSION: The results of the Mendelian randomization study suggested a potential causal relationship between napping and a reduced incidence of DVT.

The independent and combined association of napping and night sleep duration with stroke in Chinese rural adults.

BACKGROUND: Inappropriate sleep duration is a potential cause of stroke. But the effect of napping on stroke risk remains controversial and the interaction between night sleep and napping duration remains unclear. The objective of this study was to examine the independent and combined effects of napping and nocturnal sleep duration on stroke. METHODS: Subjects were derived from a rural cohort study in Henan. The Pittsburgh Sleep Quality Index (PSQI) was applied to identify nap duration and nocturnal sleep duration. Binary logistic regression was employed to indicate the dose-response relationships between naps, nocturnal sleep, total 24-h sleep duration, and stroke. RESULTS: Among the 37,341 participants (14,485 men), 2600 suffered from a stroke. The odds ratios (ORs) and 95% confidence level (CI) for stroke in the fully adjusted model were 1.37 (1.13-1.65) for men nappers compared to non-nappers. Compared to 7-8 h of sleep per day, night sleep durations < 6 h and ≥ 9 h and 24-h sleep duration ≥ 10 h were linked to increased odds of stroke in men. The ORs (95%CI) were 1.34 (1.06-1.69) in nocturnal sleep duration < 6 h, 1.30 (1.06-1.59) in nocturnal sleep duration ≥ 9 h, and 1.40 (1.15-1.71) in 24-h sleep duration ≥ 10 h in men. In addition, long naps and prolonged nocturnal sleep duration have a joint effect on stroke in the fully adjusted model. CONCLUSION: The napping duration and nocturnal sleep duration have independently and jointly effects on stroke in rural populations. More research is required to explore the underlying mechanisms for this relationship. CLINICAL TRIAL REGISTRATION: The Henan Rural Cohort Study has been registered on the Chinese Clinical Trial Register (Registration number: ChiCTR-OOC-15006699) ( http://www.chictr.org.cn/showproj.aspx?proj=11375 ).

Daytime napping and coronary heart disease risk in adults: a systematic review and dose-response meta-analysis.

PURPOSE: The present study investigated the association between daytime napping and coronary heart disease (CHD) risk among adults. METHODS: Articles were detected by using PubMed, ISI Web of Science, and Scopus databases until November 8th, 2021. The relevant data were found among the eight included articles and were pooled for meta-analysis in adult participants via a random-effects model. RESULTS: Among 167,025 adults, the results revealed that daytime napping was associated with an enhanced risk of CHD (risk ratios [RR] = 1.30; 95% CI: 1.06, 1.60; p < 0.001). Subgroup analysis by daytime napping duration also indicated that daytime napping for at least 1 h had three times higher influence on the enhanced risk of CHD (RR = 1.34; 95% CI: 1.14, 1.58; p < 0.001) than that of daytime napping for less than 1 h (RR = 1.10; 95% CI: 1.02, 1.19; p = 0.014). In addition, subgroup analysis by region illustrated that daytime napping was linked with an enhanced risk of CHD in Chinese (RR = 1.41; 95% CI: 1.19, 1.66; p < 0.001), but not in European or American populations. Furthermore, the subgroup analysis of napping duration and risk of CHD suggested that their relation was significant just in those studies that controlled for depressive symptoms (RR = 1.52; 95% CI: 1.29, 1.80; p < 0.001, n = 3) and night sleep duration (RR = 1.42; 95% CI: 1.21, 1.66; p < 0.001, n = 5). The linear dose-response meta-analysis revealed that each 15-min increase in daytime napping was related with a 5% higher risk of CHD (RR = 1.05; 95% CI: 1.02, 1.08; I2 = 58.7%; p < 0.001). Furthermore, nonlinear dose-response meta-analysis revealed a positive linear relationship between daytime napping and CHD risk in adults (p nonlinearity = 0.484, p dose-response = 0.003). CONCLUSION: Results showed that daytime napping was related with an increased risk of CHD in adults. The evidence from this study suggests that the public should be made conscious of the adverse outcomes of long daytime napping for CHD, notably among the Chinese population. Additional studies are required to confirm potential links between CHD risk and daytime napping.

Associations of daytime napping and nighttime sleep quality with depressive symptoms in older Chinese: the Guangzhou biobank cohort study.

BACKGROUND: Poor sleep quality has been linked to depression in older adults, but results of the association between daytime napping and depression remains limited and conflicting. Moreover, whether the association of daytime napping with depression varies by nighttime sleep quality is unclear. Hence, we examined the associations of daytime napping and nighttime sleep quality with depressive symptoms in older Chinese. METHODS: A total of 16,786 participants aged ≥50 from the Guangzhou Biobank Cohort Study second-round examination (2008-2012) were included in this cross-sectional study. Geriatric Depression Scale (GDS-15), Pittsburgh Sleep Quality Index (PSQI), napping and demographic data were collected by face-to-face interview using a computerized questionnaire. Logistic regression was used to calculate odds ratio (OR) of depressive symptoms for napping and sleep quality. RESULTS: The prevalence of depressive symptoms (GDS score > 5) and poor global sleep quality (PSQI score ≥ 6) was 5.3 and 31.9%, respectively. Compared to non-nappers, nappers showed significantly higher odds of depressive symptoms, with OR (95% confidence interval (CI)) being 1.28 (1.11-1.49). The odds of depressive symptoms for daytime napping varied by nighttime sleep quality (P for interaction = 0.04). In good-quality sleepers, compared to non-nappers, nappers had significantly higher odds of depressive symptoms, with OR (95% CI) being 1.57 (1.23-2.01), whereas no association was found in poor-quality sleepers (OR = 1.13, 0.94-1.36). CONCLUSION: Napping was associated with higher odds of depressive symptoms in older people, and the association was stronger in good-quality sleepers.

Associations of sleep duration, daytime napping, and snoring with depression in rural China: a cross-sectional study.

BACKGROUND: Most adult patients with depression complain about sleep symptoms, including insufficient and excessive sleep. However, previous studies investigating the impact of sleep duration on depression have yielded conflicting results. Therefore, this study aimed to analyse the link between depression and sleep duration, daytime napping, and snoring among rural Chinese adults. METHODS: A cross-sectional study was conducted with 9104 individuals. Interviews were conducted with the participants regarding their sleep patterns and their daytime napping routines. The individuals were then assessed for depression using the Patient Health Questionnaire-9. The risk of depression was assessed using a multifactor binary logistic regression analysis. A generalized additive model was used to evaluate the nonlinear relationship between depression and sleep duration/nap time. Additionally, subgroup analysis was conducted to investigate the correlation between sleep duration, daytime napping, snoring, and depression. RESULTS: Less than 6 h or more than 8 h of nighttime sleep, daytime napping for more than 1 h, and snoring were all significantly associated with an increased risk of depression. A U-shaped relationship was found between the duration of nighttime sleep and depression. In addition, we found that the nighttime duration of sleep, daytime naps, and snoring had a significant combined effect on the risk of depression. The subgroup analysis further revealed that lack of sleep at night significantly increased the risk of depression in all subgroups. However, snoring and excessive nighttime sleep and napping were only associated with the risk of depression in some subgroups. CONCLUSIONS: Lack of nighttime sleep (short sleep duration), excessive sleep, and napping for more than one hour during the day were associated with a high risk of depression and had a combined effect with snoring.

Association between internet use and depressive symptoms among older adults: mediating role of daytime napping and moderating role of productive engagement.

OBJECTIVES: This study investigated the mediating role of daytime napping in the relationship between internet use and depressive symptoms among older adults. Further the moderating effect of productive engagement was assessed on the linkage between internet use and depressive symptoms. METHODS: We surveyed 956 Chinese community-dwelling older adults. Respondents reported their internet use for different purposes (social, informational, and instrumental use), rated their levels of depressive symptoms and of daytime napping, and reported different types of/overall productive engagement. We conducted mediation and moderation analyses to test the potential pathways of associations among those factors. RESULTS: Daytime napping mediated the association between social and informational internet use and depressive symptoms. Family caregiving, sporting activities, and overall productive engagement each moderated the relationship between internet use and depressive symptoms. CONCLUSION: Internet use can increase the risk of depressive symptoms in older adults by increasing daytime napping. However, the benefits of internet use can be particularly salient for those who have a low level of productive engagement. The findings have implications for policies and practices that are designed to help older adults access the internet to enhance well-being.

Association of Midday Napping with All-Cause Mortality in Chinese Adults: A 8-Year Nationwide Cohort Study.

This study aimed to investigate the longitudinal association of estimated daytime nap duration with all-cause mortality in Chinese adults. We conceived a prospective cohort design using adult survey data of the baseline and four follow-up waves (2010-2019) from China Family Panel Studies. Cox frailty models with random intercepts for surveyed provinces were used to estimate risks of all-cause mortality associated with midday napping. Trend and subgroup analyses were also performed stratified by demographic, regional and behavioral factors. Compared with non-nappers, those who reported a long napping duration (≥60 min/day) had an increased risk of all-cause mortality, while shorter napping (<60 min) showed no association with mortality. We observed significant trends for greater risks of mortality associated with longer nap duration. Long nap-associated higher risk of all-cause mortality was seen in a group of nocturnal sleep duration ≥9 h. We identified stronger associations of long nap with mortality among adults aged over 50 years, those with lower BMI (<24 kg/m2), residents in rural regions and unregular exercisers. Long midday napping is independently associated with higher risks of all-cause mortality in Chinese adults.