Prospective association between sleep duration and cognitive impairment: Findings from the China Health and Retirement Longitudinal Study (CHARLS)

Association Between Internet Use and Sleep Health Among Middle-Aged and Older Chinese Individuals: Nationwide Longitudinal Study

BACKGROUND

Sleep disorders are common among older adults and have a bidirectional impact on their emotional well-being. While some studies suggest that internet use may offer mental health benefits to this population, the relationship between internet use and sleep outcomes remains underexplored.

OBJECTIVE

This study investigates the association between internet use (including use frequency) and sleep quality and duration in middle-aged and older Chinese adults.

METHODS

A longitudinal analysis was conducted using the China Health and Retirement Longitudinal Study data from 2015 to 2018. Sleep quality was assessed using the sleep item from the Centre for Epidemiologic Studies Depression Scale, categorized as "good" (<1 day; reference), "fair" (1-4 days), or "poor" (5-7 days). Sleep duration was classified as short (<6 hours), medium (6-9 hours; reference), or long (>9 hours). Adjusted multinomial logistic regressions were used to examine the associations between internet use or frequency in 2015 and sleep quality or duration in 2018, controlling for age, sex, residence, diseases, smoking, drinking, and napping time and further exploring sex and age group variations.

RESULTS

The baseline analysis included 18,460 participants aged 45 years and older, with 1272 (6.9%) internet users, 8825 (48.1%) participants had fair or poor sleep, and 6750 (37.2%) participants had abnormal sleep duration. Internet users, particularly those who used it almost daily, were less likely to report poor sleep quality (relative risk [RR] 0.71, 95% CI 0.54-0.94) and longer sleep duration (RR 0.22, 95% CI 0.11-0.44) than nonusers. In the longitudinal analysis, baseline internet users had a significantly reduced risk of fair (RR 0.66, 95% CI 0.51-0.86) and poor sleep quality (RR 0.60, 95% CI 0.44-0.81), as well as short (RR 0.73, 95% CI 0.53-1.00) and long sleep duration (RR 0.39, 95% CI 0.21-0.72) during the follow-up period than nonusers. These associations remained significant for almost daily internet use (RR 0.32, 95% CI 0.15-0.69). Subgroup analyses by sex revealed a positive relationship between internet use and sleep quality, with a stronger effect in female (poor sleep: RR 0.57, 95% CI 0.36-0.89) than male (poor sleep: RR 0.61, 95% CI 0.40-0.92) participants. The effect on sleep duration was significant only in daily male users, showing a reduced risk of long sleep duration (RR 0.30, 95% CI 0.11-0.78). In the age subgroup analysis, most internet users were in the 45- to 59-year age group, with results consistent with the overall findings.

CONCLUSIONS

This study suggests that internet use is associated with a reduced risk of sleep problems in middle-aged and older adults. The findings indicate that moderate, regular internet engagement-such as daily use-may promote better sleep health in this population.

Long and short sleep durations can affect cognitive function in older adults through the chain mediation effect of ADL and depression: evidence from CHARLS2018

BACKGROUND

Both long and short sleep durations may lead to cognitive decline in the elderly individuals, though the underlying mechanisms remain unclear.

AIMS

To explore the mediating mechanism of activities of daily living and depression on different sleep durations and cognitive function in older Chinese older adults.

METHODS

This retrospective study used data from 5,899 older adults who completed the 2018 China Health and Retirement Longitudinal Surveys. We used the PROCESS macro in SPSS to determine the chain mediating effect of ADL and depression on the relationship between different sleep durations and cognitive functions.

RESULTS

(1) There were significant correlations among sleep duration, ability to perform ADL, depression, and cognitive function. (2) For sleep durations ≤ 7 h/night or > 7 h/night, ADL and depression play a chain mediating role in the relationship between sleep duration and cognitive function.

CONCLUSIONS

Shorter or longer sleep durations were associated with cognitive decline by weakening ADL and worsening depression, which suggests that medical personnel should take action to correct abnormal sleep duration in older adults. Timely treatment of ADL impairment and depression may help prevent cognitive decline.

Associations between Sleep Duration and Autonomic Nervous System Regulation in Patients with Probable Alzheimer's Disease: A Cross-Sectional Pilot Study

In this study, we aimed to investigate the relationships between sleep duration and autonomic nervous system (ANS) regulation. This cross-sectional pilot study included 27 older patients with probable Alzheimer's disease who were hospitalized at a psychiatric center. We measured heart rate variability to assess ANS regulation at night, evaluated dementia severity via the Clinical Dementia Rating scale, and obtained sleep duration data from sleep diaries maintained by psychiatric nurses. The data were analyzed using repeated-measures generalized linear models with age, sex, dementia severity, hypertension status, and medication use (antipsychotics) as covariates. A sleep duration of 6-9 h per night compared to shorter than 6 h was associated with a greater increase in parasympathetic nervous system activity (p = 0.03), and a sleep duration longer than 9 h was associated with a decrease sympathovagal balance (p = 0.02). In addition, we observed an inverted U-shaped association between sleep duration and ANS regulation. In this pilot study, we demonstrated that a sleep duration of 6-9 h per night may be beneficial for ANS regulation; however, the present study involved only a few participants and had some limitations. Additional research with a larger cohort is needed to confirm these findings.

Association between nighttime sleep duration, nap time, and mild cognitive impairment in Chinese older adults: a cross-sectional study

OBJECTIVE

This study aims to investigate the relationship between midday nap time, nighttime sleep duration, and mild cognitive impairment (MCI) in Chinese older adults and determine the recommended sleep duration to provide a scientific basis for preventing and managing MCI in this population.

METHODS

Utilizing the 2020 China Health and Retirement Longitudinal Study database, the demographic data, health status, and lifestyle information of the study participants were collected. A total of 5,314 valid samples were included in the analysis. Logistic regression and restricted cubic spline plots were employed to explore the relationship between sleep patterns and MCI.

RESULTS

In the cross-sectional analysis, a linear relationship was observed between midday nap duration and MCI among Chinese elderly. The probability of MCI was lowest among those who napped for less than 30 min at noon. Compared with individuals who napped for30-90 min, those who did not nap were more likely to have MCI (OR = 1.30, 95% CI: 1.05-1.60). Older adults with napping duration < 30 min (OR = 0.73, 95% CI:0.56-0.95) also exhibited lower probability of MCI when compared those without napping habit, Nighttime sleep duration exhibited a U-shaped relationship with MCI. Individuals with less than approximately 6 h of nighttime sleep showed a gradual decrease in the probability of MCI with increasing sleep duration, whereas those with more than 7.5 h demonstrated an increase in the probability of MCI with longer sleep duration. Older adults who slept less than 6 h at night (OR = 1.22, 95% CI: 1.01 ~ 1.46) or more than 8 h (OR = 1.78, 95% CI: 1.35-2.33) were more likely to develop MCI compared with those who slept 6 to 8 h.

CONCLUSION

After controlling for potential confounding variables, both nighttime sleep duration and midday nap duration exhibited a nonlinear "U"-shaped relationship with MCI among the elderly. The probability of depression was lower with a nap duration of approximately 60 min, and the optimal nighttime sleep duration was 6-8 h, with around 7 h providing the greatest cognitive benefits.

Gender-and age-specific associations of sleep duration and quality with cognitive impairment in community-dwelling older adults in Anhui Province, China

Objective

To examine associations of sleep duration and quality with cognitive impairment in older adults and the moderating role of gender and age in these associations.

Methods

This community-based cross-sectional study included 4,837 participants aged 60 years and above. Cognitive function was assessed using the Chinese version of the Mini-Mental State Examination (MMSE), and the participants were grouped based on the presence of cognitive impairment. The duration and quality of sleep were assessed using the Pittsburgh Sleep Quality Index (PSQI). Multivariate logistic regression models were used to analyze associations of sleep duration and quality with cognitive impairment. The role of age and gender in these associations have also been explored.

Results

The age (mean ± SD) of the participants was 71.13 ± 5.50 years. Of all older adults, 1,811 (37.44%) were detected as cognitive impairment, and 1755 (36.8%) had poor sleep quality. Among those with cognitive impairment, 51.09% were female. The proportion of the participants with cognitive impairment is significantly higher in those with symptoms of depression (49.73%, 273/549) (χ2 = 41.275, p < 0.001) than in those without depressive symptoms. After adjustment for multiple confounding factors and the crucial covariate (depressive symptoms), the odds ratios (OR) (95% confidence interval [CI]) of cognitive impairment (with 7-7.9 h regarded as the reference group) for individuals with a sleep duration of <6, 6-6.9, 8-8.9, and ≥ 9 h were 1.280 (1.053-1.557), 1.425 (1.175-1.728), 1.294 (1.068-1.566), and 1.360 (1.109-1.668), respectively. Subgroup analysis showed a V-shaped association between night sleep duration and cognitive impairment in males (p ≤ 0.05), and the association was stronger for individuals aged 60-80 years. With regard to sleep quality, the fully adjusted OR (95%CI) of cognitive impairment were 1.263 (1.108-1.440). According to scores of subscales in the PSQI, daytime dysfunction was associated with an increased risk of cognitive impairment (OR: 1.128, 95%CI: 1.055-1.207). Subgroup analysis also revealed a statistically significant correlation between poor sleep quality (including daytime dysfunction) and cognitive impairment in different gender and age groups, with the association being stronger in females (OR: 1.287, 95%CI: 1.080-1.534) and those aged 81-97 years (OR: 2.128, 95%CI: 1.152-3.934). For cognitive impairment, the group aged 81-97 years with daytime dysfunction was associated with a higher odds ratio than other age groups.

Conclusion

The present study showed that inadequate or excessive sleep was associated with cognitive impairment, especially in males, who exhibited a V-shaped association. Cognitive impairment was also associated with poor sleep quality as well as daytime dysfunction, with females and individuals aged 81-97 years exhibiting the strongest association.

Association between daytime nap duration and risks of frailty: Findings from the China Health and Retirement Longitudinal Study

Introduction

Night sleep duration and total sleep duration are associated with frailty. However, the association between daytime nap duration and the risks of frailty has not been explored thoroughly.

Methods

This study used data from the China Health and Retirement Longitudinal Study (CHARLS). Participants aged 60 years and older at baseline were included in this study. Individuals with daytime nap duration were categorized into four groups: no napping, short napping (< 30 min), moderate napping (30-89 min), and extended napping (≥90 min). Frailty was assessed using a modified Physical Frailty Phenotype (PFP) scale. Non-frail participants at baseline were followed up for 4 years. The association between nap duration and risks of frailty at baseline and incident frailty was evaluated by logistic regression and discrete-time Cox regression analyses, respectively.

Results

In total, 5,126 participants were included in this study. For individuals with night sleep duration of ≥9 h, short nappers showed higher odds [odds ratio (OR) = 4.08, 95% confidence interval (CI): 1.30-12.78] for frailty compared with non-habitual nappers at baseline, while moderate nappers were less likely to be frail (OR = 0.18, 95% CI: 0.04-0.73). In the follow-up study, short nappers showed higher risks for frailty compared with participants of the no napping group with night sleep duration of < 6 h [hazard ratio (HR) = 1.91, 95% CI: 1.07-3.43] or 6-9 h (HR = 1.97, 95% CI: 1.18-3.30). Compared with short nappers, older adults with extended napping (HR = 0.41, 95% CI: 0.22-0.77) showed lower risks for frailty in those with night sleep duration of 6-9 h. For individuals with night sleep duration of ≥9 h, moderate napping (HR = 0.20, 95% CI: 0.05-0.77) decreased the risks for frailty compared with short napping.

Conclusion

Among older adults with night sleep duration of < 9 h, short nappers posed higher risks for frailty compared with non-habitual nappers. Extended naps for those with a night sleep duration of 6-9 h or moderate naps for those with night sleep duration of ≥9 h could lower the risk of frailty compared with short naps. Future studies on the timing, purpose, frequency, and quality of daytime napping and objectively measured nap duration are needed to explore the association between daytime napping and risks of frailty.