Many studies have already pointed in the past to the connection between sleep and brain health quality, but a new study offers a broader and deeper angle and tries to answer a question that concerns many people: How many hours of sleep is it really advisable to sleep in order to reduce the risk of dementia in the future.
The new study was conducted by researchers from York University in Canada and was based on a large-scale analysis of data collected from 69 previous studies. The researchers examined three key variables in lifestyle: Sleep duration, level of physical activity, and daily sitting time.
These three factors are considered to be ones that can be controlled at least to some extent, and they reflect the way people manage their daily routine in everyday life.
The statistical analysis showed that there is a sleep range that appears to be optimal when it comes to reducing the risk of dementia. According to the findings, people who sleep between seven and eight hours per night are at a lower risk level compared to those who sleep less or more than this.
Too much sleep increases the risk of dementia
The data also indicated that sleep shorter than seven hours per night was linked to an increase of about 18 percent in the risk of developing dementia later in life. In contrast, sleep longer than eight hours was linked to an even higher increase of about 28 percent.
These findings reinforce insights that have also emerged in previous studies, according to which not only lack of sleep is harmful to brain health, but also excess sleep may be problematic. In other words, when it comes to sleep, balance is the key.
However, the researchers emphasize that these are statistical correlations only and not direct proof of cause and effect. That is, it cannot be determined unequivocally that prolonged sleep causes dementia.
One of the possibilities raised in previous studies is that prolonged sleep may actually be an early sign of the development of neurodegenerative diseases such as Alzheimer’s, and not necessarily a factor that leads to them.
Prolonged daily sitting also contributes to dementia
Beyond sleep, the study also found clear links between additional daily habits and the risk of dementia. Prolonged sitting of more than eight hours per day was found to be associated with an increased risk, while low levels of physical activity, less than 150 minutes per week, were also linked to a significant increase.
According to the researchers, a combination of regular physical activity, reducing sitting time, and maintaining an appropriate sleep duration may help reduce the risk of dementia and even delay its development.
The possible explanation for this lies in the physiological effects of these habits on the body and brain. Physical activity and movement during the day help maintain proper blood flow to the brain, support neural activity, and promote the removal of cellular waste from nerve cells.
In addition, these habits also affect other systems in the body, such as the cardiovascular system, which is directly related to brain health.
Data from 4.5 million people
Although this is a study based on data analysis and not a clinical experiment, it has one significant advantage: The scope of participants. In total, the analysis included data from almost four and a half million people, which makes the findings particularly broad and significant.
Another advantage is that the data also included relatively young participants starting from age 35, which allows examining the effects of lifestyle already at an early age and not only in older age, as is done in many other studies.
However, the researchers also note several limitations. The studies included in the analysis differed from one another in data collection methods and in how the variables were defined. In addition, only a small portion of the studies specifically focused on sitting time, which highlights the need for further research in this field.
Up to half of dementia cases can be prevented or delayed
The researchers call for continued long-term studies that will examine the relationship between sleep, physical activity, and sitting habits over the years, especially among middle-aged people.
The importance of such studies is growing in light of the expected increase in the number of dementia cases worldwide in the coming years. Today there is no treatment that cures dementia, so the effort is increasingly focused on identifying risk factors that can be changed.
The estimates are that up to half of the cases can be prevented or delayed through lifestyle changes and improvement of daily habits.
In conclusion, the study joins a long line of evidence showing that our daily choices, whether it is sleep, movement, or the time we spend sitting, may significantly affect our brain health over time.
For many, this is a relatively encouraging message: Small changes in routine can accumulate into a large impact and help maintain cognitive function even in old age.