Junfeng Zhang

<h4>Background</h4>Light after dusk disrupts the circadian rhythms and shifts the timing of sleep later; but it is unknown whether outdoor artificial light at night (ALAN) affects sleep quality. This study aimed to explore the association between residential outdoor ALAN and sleep duration in a nationally representative sample of Chinese older adults.<h4>Methods</h4>We examined the cross-sectional associations of outdoor ALAN with self-reported sleep duration in 13,474 older adults participating in the 2017-2018 wave of the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Outdoor ALAN exposure was estimated at the residence level using satellite images. We applied generalized linear mixed models to investigate the association between ALAN exposure and sleep duration. We performed stratified analyses by age, sex, education, and household income levels. Moreover, we used multi-level logistic regression models to investigate the effects of ALAN on the short sleep duration (≤6 h) and the long sleep duration (>8 h), respectively, in reference to sleep for >6-8 h per day.<h4>Results</h4>We found a significant association between outdoor ALAN intensity and sleep duration. The highest quartile of ALAN was associated with 17.04 (95% CI: 9.42-24.78) fewer minutes of sleep as compared to the lowest quartile. The reductions in sleep duration per quartile change in ALAN were greater in the young old (≥65-85 years) and in those with higher levels of education, and those with higher household income, respectively. We did not detect a sex difference. In addition, those in the highest quartile of ALAN were more likely to report a 25% (95% CI: 10%-42%) increase in short sleep (<6 h), and a 21% (95% CI: 9%-31%) decrease in long sleep (>8 h).<h4>Conclusions</h4>Increasing outdoor nighttime light intensity surrounding residences was associated with shorter sleep duration in older residents in China. This finding implies the importance of urban outdoor artificial light management as a potential means to lower the public health burden of sleep disorders.

<h4>Background</h4>Despite cumulative evidence reports the interaction effects of physical activity (PA) and air pollution on lung function, the findings have been inconsistent. We aimed to identify the threshold values that reverse the beneficial effects of PA on lung function.<h4>Methods</h4>This multistage probability sampling study examined 13,032 individuals aged ≥45 years across China from 2011 to 2015. City-level particulate matter 2.5 μm or less in diameter (PM_2.5) were estimated based on a two-stage machine learning model, with a spatial resolution of 0.1° × 0.1°. We assessed PA and a range of covariates using standardized self-reported questionnaires. The peak expiratory flow (PEF) was measured using a peak flow meter. We used mixed-effects linear regression models to examine the associations between PA and PM_2.5, and their interactions with PEF.<h4>Results</h4>Participants were 60.4 ± 9.4 years old [mean ± standard deviation (SD)]. The mean ± SD of PM_2.5 and PEF was 54.4 ± 23.0 μg/m³ and 273 ± 116 L/min, respectively. Each 10 μg/m³ increase in PM_2.5 was associated with a 1.27 L/min decrease in PEF. The PEF increased by 2.48 (95% confidence interval, CI: 0.40, 4.55) L/min, 0.74 (95% CI: -1.17, 2.66) L/min, and 1.99 (95% CI: 0.001, 3.99) L/min following a 10 h/week increment of walking, moderate intensity PA, and vigorous intensity PA, respectively. Detrimental associations between PM_2.5 and PEF outweighed PA benefits for approximate PM_2.5 concentrations >81 μg/m³ (95% CI: 58.9, 111) and >77 μg/m³ (95% CI: 39.7, 102) for walking and vigorous intensity PA, respectively.<h4>Conclusions</h4>We identified the threshold of ambient PM_2.5 above which the beneficial association of PA with lung function may be reversed to an adverse one. Although the threshold may vary across populations and places, the findings suggested that reducing air pollution could enhance the benefits of PA on lung function.

IMPLICATIONS: In this study, we found several significant associations that suggest a more nuanced understanding of the potential influence of environmental- and individual-level factors for levels of prenatal smoke exposure. Results suggested a significant positive association between TRO exposure and cotinine levels, after adjusting for the individual factors such as race, education, and marital status. Individually, NDI was similarly positively associated with cotinine levels as well. However, when combining TRO exposure alongside NDI in the same model, TROs were no longer significantly associated with overall cotinine levels.

Long-term exposure to PM_2.5 has been associated with increased obesity risk, while physical activity (PA) is a suggested protective factor. This raises a dilemma whether the increased dose of PM_2.5 due to PA-intensified ventilation would offset the benefits of PA. Using a national representative sample, we aim to (1) ascertain inclusive findings of the association between PA and obesity, and (2) examine whether PM_2.5 exposure modifies the PA-obesity relationship. We recruited 91,121 Chinese adults from 31 provinces using a multi-stage stratified-clustering random sampling method. PM_2.5 was estimated using a validated machine learning method with a spatial resolution of 0.1° × 0.1°. PA intensity was calculated as metabolic equivalent (MET)-hour/week by summing all activities. Body weight, height, and waist circumference (WC) were measured after overnight fasting. Obesity-related traits included continuous outcomes (Body mass index [BMI], WC, and waist-to-height ratio (WHtR)) and binomial outcomes (general obesity, abdominal obesity, and WHtR obesity). Generalized linear regression models were used to estimate the interaction effects between PM_2.5 and PA on obesity, controlling for covariates. The results indicated that each IQR increase in PA was associated with 0.078 (95% CI: -0.096 to -0.061) kg/m², 0.342 (-0.389 to -0.294) cm, and 0.0022 (-0.0025 to -0.0019) decrease in BMI, WC, and WHtR, respectively. The joint association showed that benefits of PA on obesity were attenuated as PM_2.5 increased. Risk of abdominal obesity decreased 11.3% (OR = 0.887, 95% CI: 0.866, 0.908) per IQR increase in PA among the low-PM_2.5 (≤55.9 μg/m³) exposure group, but only 5.5% (OR = 0.945, 95% CI: 0.930, 0.960) among the high-PM_2.5 (>55.9 μg/m³) exposure group. We concluded the increase in PA intensity was significantly associated with lower risk of obesity in adults living across mainland China, where annual level of PM_2.5 were mostly exceeding the standard. Reducing PM_2.5 exposure would enhance the PA benefits as a risk reduction strategy.