Find out how finding the right balance in your sleep routine can 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 credits: fizkes/Shutterstock.com
From a recent study published in BMC Public HealthResearchers examined the relationship between afternoon nap duration, nighttime sleep duration, and mild cognitive impairment (MCI) in older Chinese adults.
Their findings indicate that both shorter and longer sleep times during the night (less than six hours or more than eight hours) and afternoon naps longer than half an hour are associated with a greater likelihood of MCI, while optimal cognitive benefits are associated with approximately seven hours nighttime sleep and a nap of less than half an hour.
Background
Cognitive disorders are becoming a major public health problem, especially as the population ages. It leads to a reduced quality of life, increased dependency and a heavy burden on caregivers. Understanding the factors that contribute to cognitive decline is essential for maintaining brain health in older adults.
Research has shown that sleep duration is related to cognitive functioning and that both insufficient and excessive sleep are associated with cognitive problems. In China, millions of elderly people 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 can cause memory impairment and brain atrophy.
Daytime naps, which are also an important part of sleep patterns, are common among the elderly in China. However, the specific impact of napping on MCI is often overlooked in research, making it a crucial area for further research 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 examine the associations between MCI and sleep duration in older Chinese adults.
Researchers focused on individuals aged 60 and older and initially selected 7,880 participants. After excluding those with incomplete data or who did not meet study criteria, 5,314 participants were included in the final analysis.
Cognitive function was assessed through face-to-face assessments, addressing orientation, memory, arithmetic, and drawing ability. MCI was defined as scoring at least one standard deviation below age-specific norms.
Sleep duration was measured using self-reported nighttime sleep and nap duration, with specific time categories for each.
Sociodemographic factors, health status and lifestyle habits were also considered as covariates.
Statistical analysis included several 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. The results showed that those who slept between six and eight hours at night had the lowest MCI rates, while those who slept more than eight hours had the highest rates.
Similarly, participants who napped for less than half an hour had the lowest MCI rates, while those who didn’t nap at all had the highest.
The study found evidence that the relationship between sleep duration and MCI is U-shaped, meaning that both too little and too much sleep increase the risk of MCI.
Specifically, less than six hours or more than eight hours of nightly sleep increased the risk of MCI compared to between six and eight hours of sleep. For naps, durations between 30 and 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, both at night and during the day, can negatively impact the cognitive health of older adults, highlighting the importance of balanced sleep patterns for cognitive maintenance.
Conclusions
This study is the first to use a large, nationally representative dataset to investigate how sleep duration – both overnight and napping – influences MCI in older Chinese adults.
A U-shaped association was found, with both too little and too much sleep increasing 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 guidance on optimal sleep duration to protect against cognitive decline in aging populations. It also addresses gaps in previous research that has often combined sleep duration, potentially missing nuanced relationships between sleep and cognition.
However, the study’s limitations include its reliance on self-reported sleep data, which can be inaccurate, especially among people with cognitive impairment. Furthermore, the cross-sectional design cannot establish causality between sleep duration and MCI risk.
Future research should use longitudinal designs and objective sleep measures to better understand the relationship between sleep and cognition.