Many health and lifestyle factors are associated with increased dementia risk, including low educational levels, smoking, physical inactivity, social isolation, hypertension, diabetes, and obesity. A study published this month in the Journal of Alzheimer's Disease found three more potential risk factors—being widowed, having lower body mass index (BMI), and getting inadequate sleep [1].
The study tracked 2,461 people aged 40-65 years old for more than 30 years. Researchers asked the participants about marital status, BMI (calculated from height and weight), smoking and alcohol consumption, physical activity, diet, and sleep at the beginning of the study. By the end of the study, 227 people had been diagnosed with dementia.
As expected, advanced age was the strongest risk factor. But the researchers also found that widowers had an increased incidence of dementia compared to married people. Widowed people often experience psychological stress, depression, and social isolation, all of which have been associated with increased dementia risk [2][3][4][5]. One caveat to this finding was that people who were widowed were more likely to be older than those who were not, and as stated above, age was the strongest risk factor for dementia. Incidentally, participants who were single, separated, or divorced did not develop dementia at a higher rate.
People who were underweight (BMI under 18.5) also had an increased dementia risk in this study. It is not clear whether low BMI alone increases risk or if it is a consequence of an underlying condition such as frailty. Other studies have reported increased dementia risk with obesity when compared to people with healthy body weight [6]. And in people with mild cognitive impairment, maintaining a normal BMI (under 25) is associated with lower levels of plaques and tangles, which are common markers of Alzheimer's disease [7].
On a more positive note, people who got at least seven hours of sleep per night had a reduced risk for dementia compared to those who got less. This finding is in line with many studies reporting that sleep deprivation and poor sleep quality are associated with increased Alzheimer's risk [8][9]. It is still unclear whether poor sleep promotes the development of Alzheimer's, or the changes Alzheimer's produces in the brain interferes with sleep, or both. Either way, ensuring that you get enough sleep is essential for long-term brain health. If you have conditions that interfere with good quality sleep such as insomnia or sleep apnea, talk to your healthcare provider about treatment options.
Identifying risk factors is the first step in reducing your chances of developing Alzheimer's or another type of dementia. The second is addressing them. This study suggests that building strong social ties, treating depression or sleep issues, and maintaining a healthy weight can all benefit brain health and reduce dementia risk.
Yuko Hara, PhD, is Director of Aging and Alzheimer's Prevention at the Alzheimer's Drug Discovery Foundation. Dr. Hara was previously an Assistant Professor in Neuroscience at the Icahn School of Medicine at Mount Sinai, where she remains an adjunct faculty member. Her research focused on brain aging, specifically how estrogens and reproductive aging influence the aging brain's synapses and mitochondria. She earned a doctorate in neurology and neuroscience at Weill Graduate School of Medical Sciences of Cornell University and a bachelor's degree in biology from Cornell University, with additional study at Keio University in Japan. Dr. Hara has authored numerous peer-reviewed publications, including articles in PNAS and Journal of Neuroscience.
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