Shift work schedule and sleep patterns in relation to incident depression: Evidence from a prospective cohort study

Replacement of sedentary behavior with various physical activities and the risk of incident depression: a prospective analysis of accelerator-measured and self-reported UK Biobank data

PURPOSE

To examine the dose‒response relationships of sedentary behavior (SB) and physical activities (PAs) with depression, and to explore the effects of replacing SB with PAs on depression risk.

METHODS

The study used data from UK Biobank aged 37 to 73 years. Light physical activity (LPA), moderate-to-vigorous activity (MVPA), sleep duration, and total sedentary behavior (TSB) were measured by accelerometers. Self-reported SB was also adopted when daily screen-sedentary behavior time (SSB) and leisure-sedentary behavior time (LSB) were the focus. Incident depression was obtained from the part of mental and behavioral disorders in the "first occurrence fields" of UK Biobank. A Cox proportional hazard model and isotemporal substitution model were performed to explore the associations of LPA, MVPA, TSB, LSB, SSB, and sleep on depression and the effects of replacing SB time with equal PA time.

RESULTS

Highest levels of MVPA (HR = 0.58, 95%CI: 0.50-0.68) were associated with decreased depression risk compared with the lowest level (Q1). Longer SSB time (HR = 1.18, 95%CI: 1.06-1.32), LSB time (HR = 1.19, 95%CI: 1.07-1.32), and TSB time (HR = 1.17, 95%CI: 1.00-1.38) could increase depression risk significantly. Replacing 1h/day TSB, SSB, and LSB with MVPA brought the greatest risk reductions [31% (HR = 0.69, 95%CI: 0.62-0.77), 30% (HR = 0.70, 95%CI: 0.65-0.77), and 29% (HR = 0.71, 95%CI: 0.65-0.77)]. Under the same conditions, the effects of LPA replacement were also significant, but weaker than those of MVPA. Subgroup analyses showed that replacing 1h/d TSB with LPA could significantly decrease the depression risk for the females, but not for the males.

CONCLUSION

Large benefits for reducing the risk of incident depression could be attained by replacing a period of TSB, SSB, or LSB with equal PA time, especially for MVPA. Regular PA and less SB were recommended for improving mental health.

Association of sleep duration with excess risk of dementia among shift workers in the UK biobank: a population-based cohort study

BACKGROUND

Shift work was associated with elevated dementia risk. Definitive guidelines for sleep duration among shift workers have not been proposed. We aimed to identify sleep durations associated with elimination of excess dementia risk in shift workers.

METHODS

285,213 dementia-free UK Biobank participants at baseline, aged 38-71 years, were enrolled between 2006 and 2010 and followed up through 2022 in this cohort study. Cox proportional hazards models were used to examine the associations between shift work, sleep duration, and risk of dementia.

RESULTS

The 285,213 participants included 49,079 shift workers and 236,134 non-shift workers. Over a median follow-up of 13.8 years, 1887 dementia cases were documented. Current shift workers had significantly higher dementia risk than non-shift workers (hazard ratio [HR] 1.26; 95% CI 1.11-1.42). However, this excess risk was eliminated in shift workers with 8 h of sleep (HR 1.02; 95% CI 0.80-1.29). Analysis of shift work frequency indicated that "sometimes" and "usually/always" shift work were associated with increased dementia risk compared to that of non-shift workers, but excess dementia risk was eliminated in members of either frequency group receiving 8 h of sleep ("sometimes", HR 1.05; 95% CI 0.75-1.48; "usually/always", HR 0.98; 95% CI 0.70-1.35). Both "non-night shift" and "night shift" workers showed increased dementia risk compared to non-shift workers. Workers with 8 h of sleep mitigated the excess risk (HR 1.13; 95% CI 0.84-1.53 and HR 0.86; 95% CI 0.59-1.26, respectively).

CONCLUSION

8-h sleep may eliminate excess dementia risk among shift workers, suggesting a potentially effective dementia prevention guideline for shift workers.

Association between cadmium exposure and serum neurofilament light chain levels: A nationwide population-based survey

BACKGROUND

Although cadmium exposure had been demonstrated to be toxic to the nervous system, little was known about the link between cadmium exposure and axonal injury. Therefore, the present study aimed to reveal whether there was any correlation between blood cadmium and serum neurofilament light chain (NfL) levels in the general population.

METHODS

This study included 1040 participants with a median (IQR) age of 47 (35-60) years from the 2013-2014 National Health and Nutrition Examination Survey. Serum NfL levels were measured through immunoassay, and whole blood cadmium concentrations were detected by means of inductively coupled plasma mass spectrometry. Linear regression and restricted cubic spline model was applied to analyze the significance of relationship between blood cadmium and serum NfL levels.

RESULTS

In the full adjusted model, blood cadmium levels were found to be positively associated with serum NfL levels (Q4 vs Q1, β = 3.35, 95 %CI: 0.41, 6.30, p for trend = 0.014). A potential linear positive dose-effect relationship was discovered between blood cadmium and serum NfL levels (p for non-linearity = 0.15). According to the result of stratified analysis, the significant positive relationship between blood cadmium and serum NfL levels was present only in the population of middle-aged and older adults.

CONCLUSION

The present study suggested a positive association between blood cadmium and serum NfL levels in the general US population.

Sleep-wake changes and incident depressive symptoms in midlife women

Our study aimed to investigate the relationship between sleep-wake changes and depressive symptoms events among midlife women. We enrolled 1579 women aged 44-56 years who had no clinically relevant depressive symptoms at baseline. Depressive symptoms were assessed at each visit using the Center for Epidemiologic Studies Depression scale. At the third and fourth follow-up visits, women reported their sleep habits. The sleep midpoint was defined as the time to fall asleep plus one-half of the sleep duration. Sleep-wake changes were determined by the difference in the midpoint of sleep between the third and fourth visits, which were 1 year apart. The median follow-up time was 7 years (range 1-7 years). Cox proportional hazard models were fitted to calculate hazard ratios and 95% confidence intervals for the incidence of depressive symptoms associated with sleep-wake changes. After adjusting for potential confounding factors, the hazard ratio (95% confidence interval) of depressive symptoms for severe sleep midpoint changes was 1.51 (1.12, 2.05) compared with mild sleep midpoint changes. This relationship remained statistically significant and changed little when additionally controlling for sleep duration, sleep quality, insomnia symptoms, use of sleep medications, use of nervous medications, glucose, insulin, lipids, dietary energy intake, and C-reactive protein. Our findings indicate that exposure to long-term severe sleep-wake changes increases the risk of depressive symptoms in midlife women.

Association and biological pathways between lung function and incident depression: a prospective cohort study of 280,032 participants

BACKGROUND

Lung health is increasingly recognized as an essential factor in mental health. However, prospective evidence on lung function with incident depression remains to be determined. The study aimed to examine the prospective association between impaired lung function and incident depression and the underlying biological mechanisms.

METHODS

This prospective cohort study comprised 280,032 non-depressed individuals with valid lung function measurements from the UK Biobank. Lung function was assessed through the forced vital capacity (FVC) or forced expiratory volume in 1 s (FEV1). Cox proportional hazard models were applied to estimate the associations between lung function and incident depression. Mediation analyses were fitted to investigate the potential mediating role of biomarkers and metabolites in the association.

RESULTS

A total of 9514 participants (3.4%) developed depression during a median follow-up of 13.91 years. Individuals in the highest quartile had a lower risk of depression (FVC % predicted: HR = 0.880, 95% CI = 0.830-0.933; FEV1% predicted: HR = 0.854, 95% CI = 0.805-0.905) compared with those in the lowest quartile of the lung function indices. Additionally, the restricted cubic splines suggested lung function indices had reversed J-shaped associations with incident depression (nonlinear P < 0.05 for FVC % predicted and FEV1% predicted). Impaired lung function yielded similar risk estimates (HR = 1.124, 95% CI = 1.074-1.176). Biomarkers involving systemic inflammation, erythrocytes, and liver and renal function may be potential mediators in the lung function-depression association.

CONCLUSIONS

This study revealed that the higher risk of developing depression was associated with impaired lung function. Also, the association might be partially mediated by biomarkers including systemic inflammation, erythrocytes, and liver and renal function, though these mediation findings should be interpreted with caution due to potential temporal ambiguity.

Exposure to residential green and blue space and the natural environment is associated with a lower incidence of psychiatric disorders in middle-aged and older adults: findings from the UK Biobank

BACKGROUND

There is increasing evidence for the role of environmental factors and exposure to the natural environment on a wide range of health outcomes. Whether exposure to green space, blue space, and the natural environment (GBN) is associated with risk of psychiatric disorders in middle-aged and older adults has not been prospectively examined.

METHODS

Longitudinal data from the UK biobank was used. At the study baseline (2006-2010), 363,047 participants (women: 53.4%; mean age 56.7 ± 8.1 years) who had not been previously diagnosed with any psychiatric disorder were included. Follow-up was achieved by collecting records from hospitals and death registers. Measurements of green and blue space modeled from land use data and natural environment from Land Cover Map were assigned to the residential address for each participant. Cox proportional hazard models with adjustment for potential confounders were used to explore the longitudinal associations between GBN and any psychiatric disorder and then by specific psychiatric disorders (dementia, substance abuse, psychotic disorder, depression, and anxiety) in middle-aged and older adults.

RESULTS

During an average follow-up of 11.5 ± 2.8 years, 49,865 individuals were diagnosed with psychiatric disorders. Compared with the first tertile (lowest) of exposure, blue space at 300 m buffer [hazard ratio (HR): 0.973, 95% confidence interval (CI): 0.952-0.994] and natural environment at 300 m buffer (HR: 0.970, 95% CI: 0.948-0.992) and at 1000 m buffer (HR: 0.975, 95% CI: 0.952-0.999) in the third tertile (highest) were significantly associated with lower risk of incident psychiatric disorders, respectively. The risk of incident dementia was statistically decreased when exposed to the third tertile (highest) of green space and natural environment at 1000 m buffer. The third tertile (highest) of green space at 300 m and 1000 m buffer and natural environment at 300 m and 1000 m buffer was associated with a reduction of 30.0%, 31.8%, 21.7%, and 30.3% in the risk of developing a psychotic disorder, respectively. Subgroup analysis suggested that the elderly, men, and those living with some comorbid conditions may derive greater benefits associated with exposure to GBN.

CONCLUSIONS

This study suggests that GBN has significant benefits for lowering the risk of psychiatric disorders in middle-aged and older adults. Future studies are warranted to validate these findings and to understand the potential mechanistic pathways underpinning these novel findings.

Mechanism of the association between sleep quality and mortality in middle-aged and older adults: A prospective study analysis of the UK Biobank

BACKGROUND

Although sleep quality is known to be associated with mortality, how poor sleep quality contributes to an increased risk of mortality is still unknown. We aimed to examine whether lifestyle, psychosocial and biological factors mediate the association.

METHODS

205,654 participants from UK Biobank were used for the analysis. The outcome was all-cause, cardiovascular disease (CVD) and cancer mortality by February 2022. Exposure was assessed by a sleep score consisting of five sleep behaviors at baseline. Lifestyle, psychosocial, and biological factors are regarded as potential mediators. Mediation analysis based on Cox proportional hazards models was performed.

RESULTS

Poor sleep quality was associated with a higher risk of all-cause (Hazard Ratio [HR] = 1.098; 95% CI: 1.058-1.140), CVD (HR = 1.139; 95% CI: 1.045-1.243) and cancer mortality (HR = 1.095; 95% CI: 1.040-1.152). Lifestyle mediators (smoking, physical activity, sedentary, BMI and diet) could explain between 2.6% and 34.0% of the increased risk of all-cause mortality in individuals with poor sleep quality. Self-reported health, frailty, depression, and loneliness were significant psychosocial mediators of this association pathway. About one-fifth of the association can be explained by the biological role of CRP. Similar mediating patterns were observed for CVD and cancer mortality.

LIMITATIONS

Both exposure and mediators were measured at baseline, so the possibility of reverse causality cannot be ruled out.

CONCLUSIONS

Poor sleep quality is associated with an increased risk of death through a combination of lifestyle, psychosocial and biological pathways. Adopting healthy lifestyles and staying psychosocial well-being are cost-effective interventions to lower the risk of death.

Association of remnant cholesterol with depression among US adults

BACKGROUND

Remnant cholesterol is receiving increasing attention because of its association with various diseases. However, there have been no studies on remnant cholesterol levels and depression.

METHODS

A cross-sectional analysis was performed based on the National Health and Nutrition Examination Survey (NHANES) 2005-2016. Depression was assessed using a Patient Health Questionnaire (PHQ-9). Fasting remnant cholesterol was calculated as the total cholesterol minus high-density lipoprotein cholesterol (HDL-C) minus low-density lipoprotein cholesterol (LDL-C). Logistic regression analysis with sampling weights was used to examine the association between remnant cholesterol concentration and depression.

RESULTS

Among 8,263 adults enrolled in this study (weighted mean age, 45.65 years), 5.88% (weighted percentage) had depression. Compared to the participants without depression, those with depression had higher concentration of remnant cholesterol (weighted mean, 26.13 vs. 23.05, P < 0.001). There was a significant positive relationship between remnant cholesterol concentration and depression and multivariable-adjusted OR with 95% CI was 1.49 (1.02-2.17). Among the subgroup analyses, remnant cholesterol concentration was positively associated with depression among participants less than 60 years (OR, 1.62; 95% CI, 1.09-2.42), male (OR, 2.02; 95% CI, 1.01-4.05), BMI under 30 (OR, 1.83; 95% CI, 1.14-2.96), and those with diabetes (OR, 3.88; 95% CI, 1.43-10.49).

CONCLUSIONS

Remnant cholesterol concentration positively correlated with depression, suggesting that a focus on remnant cholesterol may be useful in the study of depression.