Study Finds Seven Hours of Sleep Optimal for Middle-Aged and Older Adults

The research, published in Nature Aging, analyzed data from nearly 500,000 adults aged 38 to 73 in the UK Biobank. Participants shared information about their sleep patterns, mental health, and well-being and also completed cognitive tests. Brain imaging and genetic data were available for about 40,000 participants.

Findings revealed that an inadequate or excessive amount of sleep negatively affects several cognitive functions, including processing speed, memory, and problem-solving abilities. Participants sleeping for seven hours reported better mental health, experiencing fewer symptoms of anxiety and depression compared to those sleeping for shorter or longer durations.

One factor proposed for the connection between insufficient sleep and cognitive decline is the disruption of slow-wave, or 'deep,' sleep, which is crucial for memory consolidation. Disruption of this sleep stage is associated with the accumulation of amyloid protein, linked to certain types of dementia. Furthermore, insufficient sleep may impair the brain's ability to eliminate toxins.

The study also showed a correlation between sleep duration and structural differences in brain regions that are important for cognitive processing and memory. Significant changes were found in individuals who either slept more or less than seven hours.

Maintaining a consistent sleep duration of seven hours each night, with minimal fluctuation, was identified as vital for good mental health and cognitive function. Previous studies have linked disrupted sleep patterns to increased inflammation, which may contribute to age-related diseases.

Professor Jianfeng Feng from Fudan University noted that while the study does not definitively establish causation, it supports the idea that sleep duration can influence cognitive issues in older adults. The interplay of genetic factors and brain structure may complicate the reasons behind sleep difficulties in this population.

The findings suggest that both inadequate and excessive sleep could pose risks for cognitive decline in aging individuals. This aligns with earlier research linking sleep duration to the risk of developing Alzheimer's disease and dementia, conditions characterized by cognitive decline.

Professor Barbara Sahakian from the University of Cambridge emphasized the importance of sleep across all life stages, particularly in aging, and highlighted the need for strategies to improve sleep for older adults to help maintain mental health and prevent cognitive decline.

The study received support from various Chinese scientific organizations and funding programs.