Find out how striking the right balance in your sleep routine could be the key to keeping your brain sharp and preventing cognitive decline.
Study: Association between nighttime sleep duration, nap time, and mild cognitive impairment in Chinese older adults: a cross-sectional study. Image Credit: fizkes/Shutterstock.com
In a recent study published in BMC Public Health, researchers investigated the relationship between midday nap duration, nighttime sleep duration, and mild cognitive impairment (MCI) in older Chinese adults.
Their findings indicate that both shorter and longer durations of sleep during the night (less than six hours or more than eight hours) and midday naps longer than half an hour are associated with a higher likelihood of MCI, while optimal cognitive benefits are linked to approximately seven hours of nighttime sleep and a nap duration of less than half an hour.
Background
Cognitive impairment is becoming a significant public health issue, especially as the population ages. It leads to reduced quality of life, increased dependency, and a heavy burden on caregivers. Understanding the factors contributing to cognitive decline is essential for preserving brain health in older adults.
Research has shown that sleep duration is linked to cognitive functioning and that both insufficient and excessive sleep are associated with cognitive problems. In China, millions of elderly individuals suffer from MCI, a stage between normal aging and Alzheimer’s disease.
Sleep plays a crucial role in this, with short sleep durations linked to brain changes that lead to cognitive decline, while long sleep durations may cause memory impairment and brain atrophy.
Daytime naps, which are also an important part of sleep patterns, are common among elderly people in China. However, the specific impact of napping on MCI has often been overlooked in research, making it a critical area for further study to design proactive interventions to improve dementia prevention efforts.
About the study
The study used data from the 2020 China Health and Retirement Longitudinal Study (CHARLS) to investigate the associations between MCI and sleep duration among older Chinese adults.
Researchers focused on individuals aged 60 and older, initially selecting 7,880 participants. After excluding those with incomplete data or who did not meet the study criteria, 5,314 participants were included in the final analysis.
Cognitive function was assessed through face-to-face evaluations, covering orientation, memory, calculation, and drawing abilities. MCI was defined as scoring at least one standard deviation below age-specific norms.
Sleep duration was measured through self-reported nighttime sleep and nap durations, with specific time categories for each.
Sociodemographic factors, health status, and lifestyle habits were also considered as covariates.
Statistical analysis included various tests to compare groups and assess relationships between variables. Logistic regression models were used to examine the association between sleep patterns and MCI, with adjustments for demographic and health factors.
Findings
The majority of the 5,314 participants were women. Results showed that those who slept between six and eight hours at night had the lowest rates of MCI, while those who slept more than eight hours had the highest rates.
Similarly, participants who took naps of less than half an hour had the lowest MCI rates, while those who did not nap at all had the highest.
The study found evidence that the relationship between sleep duration and MCI is U-shaped, meaning both too little and too much sleep increased the likelihood of MCI.
Specifically, less than six hours or more than eight hours of nighttime sleep raised the risk of MCI compared to between six and eight hours of sleep. For naps, durations between 30-90 minutes were most protective against MCI, with a nap of around 60 minutes being optimal.
The findings suggest that both insufficient and excessive sleep, whether at night or during the day, can negatively impact cognitive health in older adults, highlighting the importance of balanced sleep patterns for cognitive preservation.
Conclusions
This study is the first to use a large, nationally representative dataset to examine how sleep duration—both nighttime and napping—affects MCI in elderly Chinese adults.
It found a U-shaped relationship, where both too little and too much sleep increased the risk of MCI. These results highlight the importance of maintaining balanced sleep patterns for cognitive health in older adults.
The study provides clear, evidence-based guidelines on optimal sleep durations to protect against cognitive decline in aging populations. It also addresses gaps in previous research that often combined sleep durations, potentially overlooking nuanced relationships between sleep and cognition.
However, the study's limitations include reliance on self-reported sleep data, which could be inaccurate, especially among those with cognitive impairments. Additionally, its cross-sectional design cannot establish causality between the duration of sleep and MCI risk.
Future research should use longitudinal designs and objective sleep measurements to understand the sleep-cognition relationship better.
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