In this episode of the Better Science Show, hosts Saleh and Fabio review a paper published in the journal Nature Communications. Titled “Association of Sleep Duration in Middle and Old Age with Incidence of Dementia,” this study offers groundbreaking insights into the complex relationship between sleep patterns and the risk of developing dementia.

Dementia Research: The 30-Year Sleep Connection

This study is notable for its scale and duration. Originating from a collaborative effort involving researchers from the United Kingdom, France, the Netherlands, and Finland, this study stands out in its approach and findings. It involved participants aged between 35 and 50 at the start, with the follow-up spanning 25 years. The use of both questionnaires and accelerometer-assessed sleep data added a layer of robustness to the findings.

The study analyzed data from approximately 8,000 participants over a period of more than 30 years. Importantly, the researchers adjusted their calculations to account for a variety of variables that could influence the development of dementia, thereby strengthening the association with sleep duration.

Previous research in this area typically involved shorter follow-up periods, often just about 10 years, which is insufficient given that signs of conditions like Alzheimer’s can appear in the brain up to 20 years before diagnosis.

This study’s extended follow-up period aimed to address this gap. Furthermore, many studies suffer from small participant numbers and a focus on older participants, which can skew results. The inclusion of mental health as a variable in the analysis is another aspect that sets this study apart.

Short Sleep Linked to Higher Dementia Risk

This study showed a 30% higher risk of dementia for individuals in their 50s and 60s who slept six hours or less per night, compared to those who had a “normal” 7-hour sleep duration. This association held even after adjusting for factors like sociodemographic, behavior, cardiometabolic health, and mental health. The researchers identified six sleep duration trajectories, among which persistent short sleep was associated with a higher dementia risk.

One of the most intriguing aspects of the study is its exploration of the reasons behind the association between sleep duration and dementia. The authors suggest several potential mechanisms, such as neuroinflammation, atherosclerosis, and impaired amyloid-b plaque clearance. They also acknowledge the limitations of their study, including its observational nature and the fact that all participants were employed, which could mean they were healthier than the general population.

While the question of whether sleep parameters affect late-life dementia remains open, this study, with its long follow-up and consideration of various factors, suggests a strong association between shorter sleep duration in midlife and increased risk of dementia. It underscores the importance of good sleep hygiene, particularly for individuals at higher risk of dementia. For anyone interested in the interplay between lifestyle factors and long-term health outcomes, this paper is must-read.

References

Sabia, S., Fayosse, A., Dumurgier, J. et al. Association of sleep duration in middle and old age with incidence of dementia. Nat Commun 12, 2289 (2021). https://doi.org/10.1038/s41467-021-22354-2