A study conducted in Washington has revealed that both insufficient and excessive sleep may contribute to cognitive decline in older adults. The research indicates that sleeping less than 4.5 hours or more than 6.5 hours per night is associated with a heightened risk of cognitive deterioration, paralleling conditions related to aging such as Alzheimer’s disease.
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The study, which enrolled older adults with significant variability in sleep duration but consistently poor sleep quality, suggests an ideal sleep range of 4.5 to 6.5 hours. These findings challenge longstanding recommendations from health organizations, which generally advocate for 7 to 8 hours of sleep per night for older adults.
Greg Elder, a senior psychology lecturer, noted that the Washington study contradicts guidance from both the NHS and the CDC, which currently do not advise against sleeping more than 6.5 hours. He pointed out that while sleep duration was linked to cognitive decline, poor sleep quality was also a common factor among participants.
The study raises questions about why sleep duration might affect brain health. One theory posits that sleep allows the brain to eliminate harmful proteins accumulated during the day, suggesting that both insufficient and excessive sleep could disrupt this cleansing process.
While the study found a correlation between longer sleep duration and cognitive decline, Elder cautioned against interpreting this relationship as causation. Factors such as underlying health issues, socioeconomic status, and physical activity levels could play a significant role and might explain the link between longer sleep and cognitive decline.
On a separate note, research from San Francisco examined a genetic trait known as Familial Natural Short Sleep (FNSS), where individuals thrive on only four to six hours of sleep. Neurologist Louis Ptacek explained that not everyone needs eight hours, as sleep needs vary based on genetics. The research emphasizes that sleep patterns can be influenced by genetic factors, further complicating the understanding of sleep duration and cognitive health.
In conclusion, while the Washington study established a connection between both inadequate and excessive sleep with cognitive decline, it also indicates the need for a more nuanced understanding of sleep. Elder advises focusing on the restorative quality of sleep rather than strictly adhering to a specific number of hours.