Monash study reveals how much sleep and activity a person needs to lower dementia risk
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Monash University researchers studied almost 90,000 people to determine the best combination of exercise and sleep to ward off developing dementia later in life. Importantly, the study found that those who sleep less than six hours a night, which has been shown to increase risk of developing dementia, can reduce this risk by simply swapping a half hour of inactivity or light activity for an extra 30 minutes of sleep.
The study, led by Professor Matthew Pase and Dr Stephanie Yiallourou from the Turner Institute for Brain and Mental Health and the School of Psychological Sciences, and published in the journal BMC Medicine investigated the effect of substituting sleep duration for different levels of physical activity (i.e. inactivity, light activity, and moderate to vigorous physical activity) in short sleepers (less than 6 hours a night) and normal sleepers (between 6 and 9 hours a night) on dementia risk and brain volumes.
The 87,490 participants in the study, enrolled in the UK Biobank, had their sleep and activity periods recorded over 24 hours for seven days. These participants, average age 63 years, were then followed for approximately eight years to determine who went on to develop dementia. The study found that, for short sleepers, increasing sleep duration was associated with a lowering of dementia risk when at the expense of inactivity or light activity, but not when at the expense of moderate to vigorous physical activity.
For normal sleepers, increasing sleep at the expense of time spent doing moderate or vigorous exercise was associated with greater dementia risk, while increasing moderate/vigorous exercise at the expense of sleep was associated with lower dementia
risk.
These findings were similar when using brain volume as an outcome in a subset of over 15,000 participants who had a brain MRI.
According to Professor Pase, both short and long sleep durations have been associated with an increased risk of dementia, with sleep having been shown to have a role in clearing amyloid beta and tau proteins, which are the hallmark signs of Alzheimer’s disease.
However, activity levels also impact dementia risk. “We wanted to determine the best target of sleep and activity to reduce dementia risk,” he said. “But as each day is only 24 hours long, changing time spent in one activity must come at the expense or gain of another. to fit in an extra half hour of moderate to vigorous physical activity, one could give up time spent sitting on the couch (e.g., inactivity), doing odd jobs around the house (e.g. light activity), or sleeping, such as waking up an hour earlier to visit the gym. The effect of each could be very different.”
In summary, the study found that individuals with very short sleep, high inactivity, and low moderate to vigorous activity had the highest rates of dementia and evidence of accelerated brain aging on MRI.
For those with short sleep duration, increasing sleep by 30 min instead of engaging in inactivity or light activity was associated with a 9 percent and 19 percent reduction in dementia risk, respectively. Dr Yiallourou said that though counterintuitive, increasing sleep at the expense of light activity rather than inactivity was more advantageous for dementia risk. “This may be because these periods of inactivity involved behaviours that were cognitively stimulating like reading,” she said.
About Monash University
Monash University is Australia’s largest university with more than 80,000 students. In the 60 years since its foundation, it has developed a reputation for world-leading high-impact research, quality teaching, and inspiring innovation.
With four campuses in Australia and a presence in Malaysia, China, India, Indonesia and Italy, it is one of the most internationalised Australian universities.
As a leading international medical research university with the largest medical faculty in Australia and integration with leading Australian teaching hospitals, we consistently rank in the top 50 universities worldwide for clinical, pre-clinical and health sciences.
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