Association between outdoor artificial light at night and sleep duration among older adults in China: A cross-sectional study

Network analysis of chronic disease among middle-aged and older adults in China: a nationwide survey

Background

Given the rising prevalence of chronic diseases and multimorbidity among middle-aged and older individuals in China, it is crucial to explore the patterns of chronic disease multimorbidity and uncover the underlying mechanisms driving the co-existence of multiple chronic conditions.

Methods

This study analyzed data from 19,206 participants in the China Health and Retirement Longitudinal Study (CHARLS 2018). The IsingFit model was used to build the chronic disease co-morbidity network, where nodes represented diseases and edges reflected conditionally independent partial correlations. Community detection identified groups of closely related diseases using the Louvain algorithm. Multivariable linear regression with forward stepwise selection explored factors influencing chronic disease co-morbidity. A random forest model ranked these factors by importance, providing insights into relationships and key contributors.

Results

This study identified the most frequent multimorbidity pairs in the middle-aged and older adult population as hypertension with arthritis, and digestive diseases with arthritis. Multimorbidities were classified into four subgroups: respiratory diseases, metabolic syndrome, neurological diseases, and digestive diseases. Heart disease showed centrality in the multimorbidity network, while memory-related diseases played a bridging role. Key factors associated with multimorbidity included age, gender, pain, sleep, physical activity, depression, and education. Random forest analysis revealed that age and pain had the greatest impact on multimorbidity development, offering insights for targeted prevention and management strategies.

Conclusion

This study systematically analyzed multimorbidity patterns and their influencing factors in the Chinese middle-aged and older adult population. The data were examined at three levels: overall network, key influencing factors, and individual characteristics. Cardio-metabolic diseases were identified as a core component of the multimorbidity network. Advanced age, pain, and depression were found to be independent risk factors affecting the number of multimorbidities, while healthy behaviors acted as significant protective factors. The study enhances understanding of multimorbidity mechanisms and provides a scientific basis for public health interventions, emphasizing the importance of behavioral modification, health education, and social support for high-risk groups.

Difference of sleep time and screen time in preschool children in rural and urban settings in natural living conditions in Japan

The amount of sleep for children has been decreasing in the past decades. Artificial light at night in home and community settings is linked with increased sleep disturbances. Recently, smartphone and tablet use has increased among children and in childcare settings. We investigated the neighborhood environment (urban vs. rural) affects sleep time, screen time usage, and melatonin and cortisol concentration in real living conditions of preschool children in Japan. In this study, 26 children aged 3-6 years from urban and rural areas in Japan were participated. We collected saliva samples for melatonin and cortisol for three times. A questionnaire was given to the parents of the children to assess smartphone and television usage, and sleep duration for two weeks. We found that television watching time was significantly longer in urban area than in rural area (181 ± 82 min/day in urban vs. 112 ± 80 min/day in rural). However, melatonin and cortisol concentrations and sleep time were not significantly different between the rural and the urban areas. These results show that urban preschool children may engage in more screen time behavior than their rural counterparts. Finally, these findings may suggest the need for education and quality improvement initiatives to promote a healthy balance between sleep and sedentary screen time in both communities.

Association between sleep characteristics and physical functioning in middle-aged and elderly adults: findings from Chinese cohorts

AIMS

Aging is associated with declines in muscle strength and physical function, and sleep plays a crucial role in maintaining musculoskeletal health. This cohort study, based on the China Health and Retirement Longitudinal Study (CHARLS), aims to explore the relationship between sleep characteristics and physical performance in middle-aged and elderly individuals.

METHODS

A total of 2,998 participants from the CHARLS cohort were included, with baseline data from the 2011 survey and follow-up data from the 2015 survey. Nighttime sleep and napping patterns were assessed, and changes in sleep duration over time were categorized. Physical functioning was assessed through handgrip strength, the chair stand test, the walking test, appendicular skeletal muscle mass, and SPPB scores. Multiple linear regression and restricted cubic spline models were employed to analyze the effects of sleep patterns on muscle health.

RESULTS

After adjusting for all confounding factors, multifactor liner regression indicated that napping durations exceeding 90 min were associated with reduced grip strength (β = -0.39, 95% CI: -1.43, -0.01, P < 0.05) and longer chair stand test times (β = 0.59, 95% CI: 0.18, 0.99, P < 0.01). The restricted cubic spline indicated a clear U-shaped relationship between nap duration and grip strength (non-linear P < 0.05), whereas no such relationship was observed between nap duration and performance on the chair stand test. In subgroup analyses addressing significant confounding factors, it was found that participants older than 65 years, males, and those with low levels of daily activity exhibited greater sensitivity to the effects of sleep on physical function. The joint analysis showed that compared to individuals with less than 6 h of nighttime sleep and no napping, those with 6-8 h of nighttime sleep and 30-90 min of napping exhibited longer chair stand test durations (β = 0.63, 95% CI: 0.06, 1.20, P < 0.05). Additionally, individuals with 6-8 h of nighttime sleep and naps exceeding 90 min showed longer walking times (β = 1.44, 95% CI: 0.68, 2.21, P < 0.01).

CONCLUSIONS

Both insufficient and excessive nighttime sleep at baseline were linked to diminished physical performance. For older adults, a nap duration approximately 50 min may be potentially optimal for maintaining grip strength. These findings highlight the importance of proper sleep management, particularly for men over 65 years old with low activity levels, in preserving physical function and reducing the risk of mobility decline.

Evaluating circadian light hygiene: Methodology and health implications

Background — A growing body of research demonstrates that a substantial daily range of light exposure, characterized by ample daylight followed by darkness during sleep, is essential for human well-being. This encompasses crucial aspects like sleep quality, mood regulation, and cardiovascular and metabolic health. Objective — This study characterizes Circadian Light Hygiene (CLH) as an essential factor in maintaining health, well-being, and longevity in modern society. CLH involves adjusting the 24-hour light exposure dynamic range to support the natural sleep-wake cycle and circadian rhythms. Three major challenges to CLH negatively impacting human health are: 1) light pollution (light at night, or LAN), characterized by excessive evening and nighttime artificial light; 2) insufficient natural daylight; and 3) irregular light exposure patterns. These interacting challenges necessitate a systematic approach to measurement and analysis. Material and Methods — A systematic review of peer-reviewed literature published through October 30, 2024, examined the methodologies and health effects of circadian and seasonal aspects of light exposure. Conclusion — This review elucidates fundamental principles of circadian light hygiene, synthesizing existing literature and our research to assess the benefits of adequate daylight, the risks of light at night, and adverse outcomes stemming from diminished light exposure range, mistimed light exposure, and irregular patterns. Novel indices for quantifying and optimizing circadian light hygiene are introduced.

Outdoor Artificial Light at Night and Insomnia-Related Social Media Posts

Importance

Understanding the outcomes of artificial light at night (ALAN) on insomnia is crucial for public health, particularly in rapidly urbanizing regions. However, evidence of the association between ALAN exposure and insomnia is limited, despite the large number of people exposed to ALAN.

Objective

To explore the association between outdoor ALAN exposure and insomnia among the Chinese population.

Design, Setting, and Participants

This cross-sectional study used social media data from Weibo (Sina), a social media platform, and satellite-derived nighttime light images. The study period spans from May 2022 to April 2023. The study encompasses 336 cities across China's mainland, providing a comprehensive national perspective. Data include insomnia-related posts from the platform users, representing a large and diverse population sample exposed to varying levels of ALAN.

Exposure

Outdoor ALAN exposure (in nanowatts per centimeters squared per steradian [nW/cm2/sr]) was measured using satellite-derived nighttime light images at a spatial resolution of 500 m.

Main Outcomes and Measures

The incidence of insomnia among residents at the city level was measured by the number of insomnia-related posts on social media. Multiple linear regression models were used to estimate the association between ALAN exposure and population insomnia, adjusting for population characteristics and meteorological factors at the city level.

Results

The study included data from 1 147 583 insomnia-related posts. Daily mean ALAN exposure across the 336 cities ranged from 3.1 to 221.0 nW/cm2/sr. For each 5 nW/cm2/sr increase in ALAN exposure, the incidence of insomnia increased by 0.377% (95% CI, 0.372%-0.382%). The association was greater in less populated cities and under extreme temperature and poor air quality conditions. The observed exposure-response functions between ALAN exposure and insomnia demonstrated an upward trend, with steeper slopes observed at low exposures and leveling off at higher exposures.

Conclusions and Relevance

This study provides evidence of the association between increased ALAN exposure and higher incidence of insomnia. These findings expand the current knowledge on adverse health outcomes of ALAN exposure and emphasize the potential health benefits of well-planned artificial nighttime lighting in China and other developing countries in the early stages of city planning.

Interactive correlations between artificial light at night, health risk behaviors, and cardiovascular health among patients with diabetes: A cross-sectional study

BACKGROUND

Artificial light at night (ALAN) is a common phenomenon and contributes to the severe light pollution suffered by more than 80% of the world's population. This study aimed to evaluate the relationship between outdoor ALAN exposure and cardiovascular health (CVH) in patients with diabetes and the influence of various modifiable factors.

METHODS

A survey method based on the China Diabetes and Risk Factor Monitoring System was adopted. Study data were extracted for 1765 individuals with diabetes in Anhui Province. Outdoor ALAN exposure (nW/cm2/sr) within 1000 m of each participant's residential address was obtained from satellite imagery data, with a resolution of ~1000 m. Health risk behaviors (HRBs) were measured via a standardized questionnaire. A linear regression model was employed to estimate the relationship between outdoor ALAN, HRBs, and CVH.

RESULTS

Participants' mean age was 59.10 ± 10.0 years. An association was observed between ALAN and CVH in patients with diabetes (β = 0.205) and exercise (β = -1.557), moderated by HRBs, or metabolic metrics. There was an association between ALAN, ALAN, vegetable intake, and CVH.

CONCLUSIONS

Exploring the relationship between ALAN exposure and cardiovascular and metabolic health provides policy data for improving light pollution strategies and reducing the risk of cardiovascular and metabolic disease in patients with diabetes.

Confounding associations between green space and outdoor artificial light at night: Systematic investigations and implications for urban health

Excessive urbanization leads to considerable nature deficiency and abundant artificial infrastructure in urban areas, which triggered intensive discussions on people's exposure to green space and outdoor artificial light at night (ALAN). Recent academic progress highlights that people's exposure to green space and outdoor ALAN may be confounders of each other but lacks systematic investigations. This study investigates the associations between people's exposure to green space and outdoor ALAN by adopting the three most used research paradigms: population-level residence-based, individual-level residence-based, and individual-level mobility-oriented paradigms. We employed the green space and outdoor ALAN data of 291 Tertiary Planning Units in Hong Kong for population-level analysis. We also used data from 940 participants in six representative communities for individual-level analyses. Hong Kong green space and outdoor ALAN were derived from high-resolution remote sensing data. The total exposures were derived using the spatiotemporally weighted approaches. Our results confirm that the negative associations between people's exposure to green space and outdoor ALAN are universal across different research paradigms, spatially non-stationary, and consistent among different socio-demographic groups. We also observed that mobility-oriented measures may lead to stronger negative associations than residence-based measures by mitigating the contextual errors of residence-based measures. Our results highlight the potential confounding associations between people's exposure to green space and outdoor ALAN, and we strongly recommend relevant studies to consider both of them in modeling people's health outcomes, especially for those health outcomes impacted by the co-exposure to them.

Association between sleep duration and possible sarcopenia in middle-aged and elderly Chinese individuals: evidence from the China health and retirement longitudinal study

BACKGROUND

Sarcopenia is a common cause of disability in the aging population, and managing sarcopenia is an important step in building intrinsic capacity and promoting healthy aging. A growing body of evidence suggests that sleep deprivation may be a mediator of the development of sarcopenia. The purpose of this study was to explore the longitudinal association between sleep duration and possible sarcopenia using data from a national sample.

METHODS

Two waves of data from the CHARLS database for 2011 and 2015 were used in this study. All possible sarcopenia participants met the Asia Working Group for Sarcopenia 2019 (AWGS 2019) diagnostic criteria. Sleep duration was assessed using a self-report questionnaire, and sleep duration was categorized as short (≤ 6 h), medium (6-8 h), or long (> 8 h) based on previous studies. Longitudinal associations between sleep duration and possible sarcopenia will be calculated by univariate and multifactorial logistic regression analyses and expressed as odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

A total of 5654 individuals participated in the follow-up study, with a prevalence of possible sarcopenia of 53.72% (578) in the short sleep duration group, 38.29% (412) in the medium sleep duration group, and 7.99% (86) in the long sleep duration group. According to the crude model of the second-wave follow-up study, short sleep durations were significantly more strongly associated with possible sarcopenia than were medium and long sleep durations (OR: 1.35, 95% CI: 1.17-1.55, P = 0.000). The association between short sleep duration and possible sarcopenia was maintained even after adjustment for covariates such as age, gender, residence, education level, BMI, smoking status, alcohol consumption and comorbidities (OR: 1.18, 95% CI: 1.02-1.36, P = 0.029). In the subgroup analysis, short sleep duration was associated with low grip strength (OR: 1.20, 95% CI: 1.02-1.41, P = 0.031).

CONCLUSIONS

Sleep deprivation may be closely associated with the development of possible sarcopenia in middle-aged and elderly people, which provides new insights and ideas for sarcopenia intervention, and further studies are needed to reveal the underlying mechanisms involved.

Outdoor Artificial Light at Night and Reproductive Endocrine and Glucose Homeostasis and Polycystic Ovary Syndrome in Women of Reproductive Age

BACKGROUND

Artificial light at night, a well-recognized circadian clock disrupter, causes disturbances in endocrine homeostasis. However, the association of artificial light at night with polycystic ovary syndrome (PCOS) is still unknown. This study examines the effects of outdoor artificial light at night on sex hormones, glucose homeostasis markers, and PCOS prevalence in Anhui Province, China.

METHODS

We recruited 20,633 women of reproductive age from Anhui Medical University Reproductive Medicine Center. PCOS was diagnosed according to Rotterdam criteria. We estimated long-term (previous year) and short-term (previous month) artificial light at night values for residential addresses using 500 m resolution satellite imagery. We fitted multivariable models, using both linear and logistic regression, to estimate the association of artificial light at night with sex hormones, glucose homeostasis markers, and PCOS prevalence.

RESULTS

Both long-term and short-term exposure to outdoor artificial light at night were negatively associated with follicle-stimulating hormone and luteinizing hormone levels, while positively associated with testosterone, fasting insulin, homeostasis model assessment-insulin resistance, and homeostasis model assessment-insulin resistance-β levels. The second-highest quintile of artificial light at night was associated with increased PCOS prevalence (odds ratio [OR long-term ] = 1.4; 95% confidence interval [CI] = 1.2, 1.6 and OR short-term = 1.3; 95% CI = 1.1, 1.5) compared with the lowest quintile. In addition, prevalence of PCOS was linearly associated with long-term exposure to artificial light at night, but nonlinearly associated with short-term exposure. This association was more evident in younger, obese or overweight, moderately educated, rural women, and for the summer and fall seasons.

CONCLUSION

Outdoor artificial light at night may be a novel risk factor for PCOS.

Outdoor artificial light at night exposure and gestational diabetes mellitus: a case-control study

Objective

This study aims to explore the association between outdoor artificial light at night (ALAN) exposure and gestational diabetes mellitus (GDM).

Methods

This study is a retrospective case-control study. According with quantiles, ALAN has been classified into three categories (Q1-Q3). GDM was diagnosed through oral glucose tolerance tests. Conditional logistic regression models were used to evaluate the association between ALAN exposure and GDM risk. The odds ratio (OR) with 95% confidence interval (CI) was used to assess the association. Restricted cubic spline analysis (RCS) was utilized to investigate the no liner association between ALAN and GDM.

Results

A total of 5,720 participants were included, comprising 1,430 individuals with GDM and 4,290 matched controls. Pregnant women exposed to higher levels of ALAN during the first trimester exhibited an elevated risk of GDM compared to those with lower exposure levels (Q2 OR = 1.39, 95% CI 1.20-1.63, p < 0.001); (Q3 OR = 1.70, 95% CI 1.44-2.00, p < 0.001). Similarly, elevated ALAN exposure during the second trimester also conferred an increased risk of GDM (second trimester: Q2 OR = 1.70, 95% CI 1.45-1.98, p < 0.001; Q3 OR = 2.08, 95% CI 1.77-2.44, p < 0.001). RCS showed a nonlinear association between ALAN exposure and GDM risk in second trimester pregnancy, with a threshold value of 4.235.

Conclusion

Outdoor ALAN exposure during pregnancy is associated with an increased risk of GDM.

Racial/ethnic and sex differences in the association between light at night and actigraphy-measured sleep duration in adults: NHANES 2011-2014

OBJECTIVE

Historically minoritized individuals experience greater exposure to light at night, yet it is unclear whether the association between light at night and sleep duration vary by race/ethnicity or sex. We examined the association between light at night and sleep duration by race/ethnicity and sex.

METHODS

Participants (N = 6089, mean age=49.5, 52% women, 13% Asian, 27% Black, 14% Mexican, 46% White) in the 2011-2014 National Health and Nutrition Examination Survey underwent 9-day of actigraphy. Light at night was defined as light exposure within the 5-hour activity nadir (L5). Sleep duration within a 24-hour period was analyzed as short (<7 hours) or long (>9 hours) compared to recommended (≥7 and <9 hours). Poisson models were fit to estimate the association between light at night and sleep duration after adjustment for covariates.

RESULTS

Light at night was most common among Black participants, who also had the shortest sleep duration. Overall, light at night was associated with 80% higher prevalence of short sleep duration [1.80 (1.49, 2.18)]. Compared to no-light at night, low and high light at night were associated with higher prevalence of short sleep duration, [1.61 (1.31, 1.98) and 2.01 (1.66, 2.44), respectively]. Associations varied by race/ethnicity and sex. Light at night was associated with shorter sleep duration in Black, Mexican and White females and Mexican and White males only. Black males exposed to light at night vs. no-light at night had lower prevalence of long sleep duration. There were no associations between light at night and sleep duration among Asian participants.

CONCLUSION

Light at night was associated with shorter sleep duration, particularly among females. Targeting light exposure may help to improve sleep duration.

Association Between Bedroom Light Pollution With Subjectively and Objectively Measured Sleep Parameters Among Chinese Young Adults

PURPOSE

To investigate the cross-sectional associations between real-world multiperiod bedroom light at night and sleep parameters among 365 Chinese young adults.

METHODS

Bedroom light exposure was estimated at the individual level for two consecutive days using a portable illuminance meter. Subjective sleep parameters were measured with the Pittsburgh Sleep Quality Index, and objective sleep parameters were assessed by wrist-worn ActiGraph accelerometers for seven consecutive days.

RESULTS

Compared with the low-exposure group (average light intensity < 3lx), the high-exposure group (average light intensity ≥ 3lx) was associated with decreased 1.15% in sleep efficiency (sleep efficiency, 95% CI: -1.78, -0.52; p < .001), increased 3.94 minutes in wake after sleep onset (wake after sleep onset, 95% CI: 1.55, 6.33; p = .001), increased 1.05 unit in movement index (95% CI: 0.20, 1.89; p = .015), and increased 2.16 unit in sleep fragmentation index ( 95% CI: 0.63, 3.68; p = .006). In comparison, each interquartile increase in 2h-average and 1h-average intensity of preawake light (PAL) (PAL-2h and PAL-1h) was associated with 7.04 minutes of increases in total sleep time (95% CI: 0.87, 13.22; p = .025) and 6.69 minutes of increases in total sleep time (95% CI: 0.51, 12.87; p = .034), respectively.

DISCUSSION

Altogether, our results support the role of bedroom light exposure in sleep and imply the importance of bedroom light exposure management as a potential strategy to reduce the public health burden of sleep problems. Keeping the bedroom environment dark at night and allowing moderate morning light exposure may be important measures for improving the sleep quality of young adults.

Short sleeping duration is associated with a higher risk of asymmetric handgrip strength among older Chinese males: a cross-sectional study evidence from the China health and retirement longitudinal study

Objective

This study aimed to explore the potential correlation between sleeping duration and the risk of handgrip strength (HGS) asymmetry in older Chinese adults.

Methods

The data of participants (65+ years of age) were obtained from the first Wave 1 (2011) of the China Health and Retirement Longitudinal Study (CHARLS). Information on sleeping duration during the previous month was collected from self-reports and was divided into three groups: long (>8 h), normal (6-8 h), and short (< 6 h). HGS was computed as the average of two tests per hand and asymmetric HGS was diagnosed when the ratio of average non-dominant to average dominant HGS was greater than 1.1 or less than 0.9. Logistic regression analyses were employed to gauge the relationship between sleeping duration and asymmetric HGS risk.

Results

In total, 3,174 participants were enrolled in this analysis, of whom 51.54% (1,636/3,174) were male. The proportions of asymmetric HGS were 42.18% in males and 41.87% in females. The sleeping duration (hours) in the asymmetric and non-asymmetric HGS groups were 6 h (5,8) and 7 h (5,8) in males with a significant difference between them (p = 0.015), and 6 h (5,8) and 6 h (5,8) in females with no significant difference (p = 0.415). Compared with non-asymmetric HGS individuals, the proportions of normal, short, and long sleeping duration were 40.4, 47.3, and 37.7% in males with a significant difference (p = 0.023), and 42.4, 40.3, and 43.8% in females with no significant differences (p = 0.685). An adjusted logistic regression analysis model confirmed that short sleeping duration was significantly associated with asymmetric HGS risk among older males (p = 0.048, OR = 1.252, 95%CI:1.002-1.565).

Conclusion

The results demonstrated that short sleeping duration (<6 h) was a risk factor for increased HGS asymmetry among older Chinese males.

Association of outdoor artificial light at night with metabolic syndrome and the modifying effect of tree and grass cover

BACKGROUND

Epidemiological studies show that outdoor artificial light at night (ALAN) is linked to metabolic hazards, but its association with metabolic syndrome (MetS) remains unclear. We aimed to investigate the association of outdoor ALAN with MetS in middle-aged and elderly Chinese.

METHODS

From 2017-2020, we conducted a cross-sectional study in a total of 109,452 participants living in ten cities of eastern China. MetS was defined by fasting blood glucose (FG), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), blood pressure (BP), and waist circumference (WC). In 2021, we followed up 4395 participants without MetS at the baseline. Each participant's five-year average exposure to outdoor ALAN, as well as their exposure to green space type, were measured through matching to their address. Generalized linear models were used to assess the associations of outdoor ALAN with MetS. Stratified analyses were performed by sex, age, region, physical activity, and exposure to green space.

RESULTS

In the cross-sectional study, compared to the first quantile (Q1) of outdoor ALAN exposure, the odds ratios (ORs) of MetS were 1.156 [95 % confidence interval (CI): 1.111-1.203] and 1.073 (95 %CI: 1.021-1.128) respectively in the third and fourth quantiles (Q3, Q4) of outdoor ALAN exposure. The follow-up study found that, compared to the first quantile (Q1) of outdoor ALAN exposure, the OR of MetS in Q4 of ALAN exposure was 1.204 (95 %CI: 1.019-1.422). Adverse associations of ALAN with MetS components, including high FG, high TG, and obesity, were also found. Greater associations of ALAN with MetS were found in males, the elderly, urban residents, those with low frequency of physical activity, and those living in areas with low levels of grass cover and tree cover.

CONCLUSIONS

Outdoor ALAN exposure is associated with an increased MetS risk, especially in males, the elderly, urban residents, those lacking physical activity, and those living in lower levels of grass cover and tree cover.

The association between long-term exposure to outdoor artificial light at night and poor sleep quality among Chinese veterans: A multi-city study

BACKGROUND

A handful of previous studies have reported the association between exposure to outdoor artificial light at night (ALAN) and sleep problems. However, evidence for such association is limited in low- and middle-income countries. This study aimed to examine the association between outdoor ALAN exposure and sleep quality in veterans across different regions of China.

METHODS

Within the network of the Chinese Veteran Clinical Research Platform, we selected 7258 participants from 277 veteran communities in 18 cities across China during December 2009 and December 2011, using a multi-stage stratified cluster sampling strategy. Face-to-face interviews with the participants were conducted by trained investigators. We used the Pittsburgh Sleep Quality Index (PSQI) to assess participants' sleep quality. We defined poor sleep quality as a PSQI global score >7. The 3-year average exposure to outdoor ALAN prior to the baseline interview was calculated using satellite imagery data, according to participants' geolocation information. The association of ALAN exposure with sleep quality was examined using the mixed-effects logistic regression models with natural cubic splines.

RESULTS

The exposure-response curve for sleep quality associated with ALAN exposure was nonlinear, with a threshold value of 49.20 nW/cm2/sr for the 3-year average exposure to outdoor ALAN prior to the baseline interview. Higher ALAN exposure above the threshold was associated with increased risk of poor sleep quality. After adjusting for potential confounders, the odds ratios (and 95%CI, 95% confidence intervals) were 1.15 (0.97, 1.36) and 1.45 (1.17, 1.78) at the 75th and 95th percentiles of ALAN against the threshold. The association of ALAN exposure with poor sleep quality was more pronounced in veterans with depression than those without. Higher OR of poor sleep quality at the 75th percentile of ALAN against the threshold was observed in veterans with depression than those without [2.09 (1.16, 3.76) vs. 1.09 (0.92, 1.30)].

CONCLUSIONS

Long-term exposure to outdoor ALAN was associated with higher risk of poor sleep quality in Chinese veterans. Effective outdoor ALAN management may help to reduce the burden of sleep disorders in Chinese veterans.

Outdoor light at night, genetic predisposition and type 2 diabetes mellitus: A prospective cohort study

BACKGROUND

According to animal and human epidemiologic studies, exposure to outdoor light at night (LAN) may cause circadian disruption, which may disturb sleep quality and lead to incident type 2 diabetes mellitus (T2DM).

METHODS

We followed 283,374 persons from 2006 through 2020. Outdoor LAN exposure was estimated using satellite data for individual address with 500 m² scale buffer during follow-up. Incidence of T2DM was confirmed by hospital inpatient records. We identified potential confounders by a directed acyclic graph, including demographic, genetic, individual and regional level socioeconomic status, and environmental risk factors, and calculated hazard ratios (HRs) and 95% confidence intervals (CIs) through time-varying Cox proportional hazard model. Furthermore, we examined the association of outdoor LAN with a defined health sleep scores and moderation of genetic predisposition and shift work on the relationship of outdoor LAN and incident T2DM.

RESULTS

We identified 7,775 incident T2DM cases over 3,027,505 person-years. Higher outdoor LAN exposures were significantly associated with higher risk of T2DM. The estimated HR for incident T2DM with an interquartile range (IQR: 11.22 nW/cm²/sr) increase in outdoor LAN was 1.05 (95%CI: 1.01, 1.09) in the fully adjusted model. Participants who lived in the highest quarter of outdoor LAN area were more likely to develop T2DM (HR: 1.14,95%CI: 1.02, 1.27). Besides, those who were exposed to higher levels of outdoor LAN had poorer sleep quality. No moderation role of PRS on outdoor LAN-induced T2DM observed both on the multiplicated and additive scale. The hazards of outdoor LAN were observed in those who never owned a night shift work.

CONCLUSION

Although further work is required to clarify potential mechanisms, our findings indicate that exposure to residential outdoor LAN may contribute to T2DM risk and low sleep quality.

Outdoor artificial light at night and human health: A review of epidemiological studies

We conducted a non-systematic review of epidemiological studies on a potential link between exposure to outdoor artificial light at night (O-ALAN) and disease occurrence in humans published since 2009. In recent years, a number of presses have been published on this issue, but the conclusions have been mixed. We therefore decided to critically analyze the available epidemiological evidence of such a correlation. After a careful search, 51 studies were identified and included in the review. They addressed the potential link between O-ALAN exposure and the incidence of breast cancer, other cancers, sleep and circadian rhythm disorders, obesity and cardiovascular diseases, mental disorders, infectious diseases, and complications during pregnancy and childbirth. The vast majority of papers revealed the existence of such a link. However, the amount of epidemiological evidence supporting the correlation across groups of disorders varied widely. In addition, we found that all papers contained at least one of the following omissions: lack of the temporal and spatial resolution in light at night measurements, measuring only light intensity without considering its wavelength, and not accounting for many important confounding factors in their statistical analyses. Therefore, we believe that the link between O-ALAN exposure and the occurrence of the disorders in question suggested by the authors of the reviewed papers may be in some cases at least to some extent, a coincidence. Further epidemiological studies, free of significant omissions highlighted in this paper, are needed.

Sleep Health as a Determinant of Disparities in Stroke Risk and Health Outcome

Sleep is essential to human survival and overall vascular health. Sleep health encompasses the objective and subjective qualities associated with one's daily pattern of sleep and wakefulness and has become a growing clinical and public health concern. Impaired sleep duration and quality can increase stroke risk and mediate the relationship between the physical aspects of an individual's environment and disparities in stroke incidence. Here, we review observational studies evaluating the association between sleep health and cerebrovascular disease. We assess the influence on sleep of the physical environment, including the ambient environment with noise levels and the built environment. We also describe the influences on sleep health and stroke risk of social determinants of health, including the chronic stressor of racial discrimination. Finally, we discuss how changes in historical neighborhood characteristics or societal policies can influence the social factors affecting sleep health and stroke risk among socioeconomically disadvantaged groups or ethnic and racial minorities. Given the regional and racial or ethnic differences in stroke risk across the United States, an understanding of novel vascular risk factors, such as the multifaceted role of sleep health, will be critical to develop effective public policies to improve population health.

Association between exposure to light at night (LAN) and sleep problems: A systematic review and meta-analysis of observational studies

BACKGROUND

Accumulating evidence have investigated the effects of nighttime light exposure on sleep problems. Nevertheless, the evidence of the relationship between light at night (LAN) and sleep problems remains scarce and inconsistent.

OBJECTIVE

Conducted a systematic review and meta-analysis based on observational studies to examine the association between LAN exposure and sleep problems among human subjects.

METHODS

We systematically searched three databases (PubMed, Web of Science, and Embase) to identify potentially eligible studies through May 25, 2022. The risk of bias and the quality of the generated evidence were assessed by two authors using the National Toxicology Program's Office of Health Assessment and Translation (OHAT) risk of bias rating tool and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guideline. Random-effects model was applied to synthesize the risk estimates across eligible studies. The heterogeneity of included studies was quantified by the statistics of I².

RESULTS

A total of 7 cross-sectional studies comprising 577,932 participants were included. Individuals with higher levels of LAN exposure were associated with a 22 % (Summary Odds Ratio, SOR: 1.22, 95 %CI: 1.13-1.33) increased prevalence of sleep problems. The pooled effect size of indoor LAN exposure (SOR: 1.74, 95%CI: 1.27-2.37) associated with sleep problems was significantly higher than outdoor LAN exposure (SOR: 1.19, 95%CI: 1.11-1.29; P = 0.022). Additionally, dose-response analysis demonstrated that LAN intensity threshold exceeding 5.8 nW/cm²/sr (SOR: 1.04, 95%CI: 1.01-1.07) had a significant effect on sleep problems and the prevalence of sleep problems was increasing with increase in LAN intensity.

CONCLUSIONS

Overall, our findings support the detrimental effects of LAN exposure on sleep. Maintaining bedroom darkness at night may be a feasible measure to reduce the prevalence of sleep problems. Future longitudinal studies with more advanced LAN assessment methods are required to move the field forward.

Examining the influence of built environment on sleep disruption

Modifying aspects of the built environment may be an effective strategy for population-level improvements to sleep. However, few comprehensive evaluations of built environment and sleep have been completed.

Methods

We conducted a cross-sectional study among participants of the British Columbia Generations Project (BCGP) who self-reported sleep duration (n = 28,385). Geospatial measures of light-at-night (LAN), greenness, air pollution (PM_2.5, NO₂, SO₂), and road proximity were linked to participant baseline residential postal codes. Logistic regression models, adjusted for age and sex, were used to estimate the association between these factors and self-reported sleep duration (<7 vs. ≥7 hours).

Results

Interquartile range (IQR) increases in LAN intensity, greenness, and SO₂ were associated with 1.04-fold increased (95% CI = 1.02, 1.07), 0.95-fold decreased (95% CI = 0.91, 0.98), and 1.07-fold increased (95% CI = 1.03, 1.11) odds, respectively, of reporting insufficient sleep (i.e., <7 hours per night). Living <100 m from a main roadway was associated with a 1.09-fold greater odds of insufficient sleep (95% CI = 1.02, 1.17). Results were unchanged when examining all factors together within a single regression model. In stratified analyses, associations with SO₂ were stronger among those with lower reported annual household incomes and those living in more urban areas.

Conclusions

BCGP's rich data enabled a comprehensive evaluation of the built environment, revealing multiple factors as potentially modifiable determinants of sleep disruption. In addition to longitudinal evaluations, future studies should pay careful attention to the role of social disparities in sleep health.