Study Finds Lifestyle Changes May Reduce Dementia Risk by Up to 25 Percent

A study published on Wednesday in the journal PLOS One examined the impact of lifestyle factors on dementia risk. Researchers analyzed data from 69 studies that included nearly 3 million participants, with an average age of 67 years. All participants resided in high-income countries, including the United States, and the studies followed individuals for periods ranging from one year to 11 years.

The analysis focused on habits beginning at age 35 and their association with dementia risk later in life. Seventeen of the studies addressed sleep duration. The research identified seven to eight hours of sleep per night as associated with optimal brain health.

Sleeping less than seven hours per night was linked to an 18 percent increase in dementia risk. Sleeping more than eight hours per night was associated with a 28 percent increase in risk. The remaining studies investigated physical activity and sedentary behavior, such as prolonged sitting at work.

Sitting for more than eight hours a day was associated with nearly a 30 percent increase in dementia risk. Regular physical activity, including daily walking, was linked to an average 25 percent decrease in risk. Breaking up longer periods of sitting showed the greatest effect on reducing risk.

The study estimated that implementing these lifestyle changes could reduce the average person's dementia risk from 11 percent to 8 percent. About 1 in 9 people in the United States develop Alzheimer's disease, according to the Alzheimer’s Association.

The reduction in risk is comparable to effect sizes observed with medications for chronic diseases, according to Akinkunle Oye-Somefun, a researcher at York University in Toronto who led the study.

“You don’t need to be perfect, but if you have a lot of sedentary time in your day, getting a bit of exercise, even if that’s just going for a walk, will have a long-term benefit for the brain.”

Moderate physical activity was found to offset dementia risks even when other risk factors were present, Oye-Somefun stated. Prolonged sitting can contribute to cardiovascular disease, diabetes, and obesity, conditions that elevate dementia risk. Physical activity alone does not fully mitigate the effects of extended sedentary periods, according to the study.

Exercise increases blood flow and oxygen to the brain through muscle contractions, which release brain-derived neurotrophic factor, or BDNF. This protein supports cognitive function, neuron generation, and connections in the hippocampus, the brain region involved in memory conversion.

Breaking up sitting with standing or walking improves blood flow and may prevent brain atrophy, as noted by Amal Wanigatunga, an assistant professor of epidemiology at Johns Hopkins Bloomberg School of Public Health.