Dementia, a growing global health concern, currently affects over 55 million people worldwide, with projections estimating that 139 million individuals will have dementia by 2050. While numerous factors influence dementia risk, including physical inactivity, high blood pressure, and uncontrolled diabetes, sleep disturbances have also been suggested as contributing factors. However, studies disagree on whether excessive or insufficient sleep poses a greater risk.
Recent research from the University of California, San Francisco, sheds light on the connection between sleep patterns and dementia. The study, published in Neurology, involved 733 women in their 80s who wore sleep trackers for five years. The findings reveal that increased daytime sleepiness, particularly excessive napping, may double the risk of developing dementia.
Sleep Duration and Cognitive Decline: What the Research Shows
Sleep duration has long been a topic of interest in dementia studies. Past research has found that both long and short sleep durations are associated with an elevated risk of cognitive decline. One study suggests that insufficient sleep during middle age can increase dementia risk, while another links excessive sleep (more than 9 hours a night) to neurodegeneration. However, these studies were based on self-reported data rather than objective measures.
The recent study from UCSF used sleep trackers to monitor participants’ sleep-wake cycles, providing more accurate data. Researchers observed three distinct sleep profiles: stable sleep, declining nighttime sleep, and increasing sleepiness. Those in the increasing sleepiness category had significantly higher odds of developing dementia over the five-year period.
A Deeper Look: Why Excessive Sleep May Signal Dementia
The study participants, aged 65 and older, were initially cognitively healthy. They wore wrist monitors that measured their sleep-wake patterns and participated in sleep logs. By the end of the five years, 22.4% of the women developed mild cognitive impairment (MCI), while 12.7% were diagnosed with dementia. Women who exhibited increased daytime sleepiness had a twofold risk of developing dementia compared to those with stable sleep patterns. However, increased sleepiness was not linked to a higher risk of MCI.
This research supports previous findings suggesting that disrupted sleep patterns, such as excessive daytime sleepiness, might signal early neurodegenerative changes. According to Dr. Steve Allder, a consultant neurologist, excessive daytime sleep could be a response to brain changes in areas that regulate sleep, such as the hypothalamus and brainstem. Furthermore, poor sleep quality can lead to amyloid-beta accumulation, a hallmark of Alzheimer’s disease, exacerbating cognitive decline.
Implications for Dementia Prevention and Sleep Hygiene
While the study’s observational nature cannot confirm a direct cause-and-effect relationship, it emphasizes the importance of maintaining healthy sleep patterns. Dr. Ben Dunkley, a cognitive neuroscientist, recommends lifestyle changes to improve sleep quality, including maintaining consistent sleep schedules, limiting alcohol consumption, and optimizing sleep hygiene. These habits, combined with technologies like wearable sleep trackers, can help individuals monitor and improve both sleep and cognitive health, potentially reducing dementia risk.
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