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Dementia risk higher for underweight middle-aged adults
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An increased risk for dementia during a 15-year period is associated with being underweight in middle and old age, according to recent study findings published in The Lancet Diabetes & Endocrinology.
These results contradict previous findings that obesity in middle age could increase the risk for dementia in older age, according to the researchers.
“Our results suggest that doctors, public health scientists and policymakers need to rethink how to best identify who is at high risk of dementia,” Stuart Pocock, BSc, MSc, PhD, of the London School of Hygiene & Tropical Medicine, said in a press release. “We also need to pay attention to the causes and public health consequences of the link between underweight and increased dementia risk [that] our research has established. However, our results also open up an intriguing new avenue in the search for protective factors for dementia — if we can understand why people with a high BMI have a reduced risk of dementia, it’s possible that further down the line, researchers might be able to use these insights to develop new treatments for dementia.”
The researchers evaluated 1,958,191 adults aged at least 40 years from the United Kingdom Clinical Practice Research Datalink whose BMI was recorded between 1992 and 2007 to determine the relationship between BMI and risk for dementia. Participants were followed until the practice’s final data collection date, patient death or transfer out of practice, or first record of dementia.
Standard BMI definitions were used to evaluate participants: underweight (< 20 kg/m2), healthy weight (20-24.9 kg/m2), overweight (25-29.9 kg/m2) and obese (≥ 30 kg/m2). Median BMI of participants was 26.4 kg/m2.
Overall, 45,507 participants had a first diagnosis of dementia during a median follow-up of 9.1 years.
A 34% increased risk for dementia was found for underweight participants compared with healthy-weight participants. The risk for dementia decreased with each increasing BMI category; a 29% lower risk for dementia was found among participants with severe obesity (≥ 40 kg/m2) compared with participants with a healthy weight.
“The reasons why high BMI might be associated with a reduced risk of dementia aren’t clear, and further work is needed to understand why this might be the case,” Nawab Qizilbash, MBChB, MRCP, BSc, MSc, DPhil, of OXON Epidemiology and the London School of Hygiene & Tropical Medicine, said in the release. “If increased weight in midlife is protective against dementia, the reasons for this inverse association are unclear at present. Many different issues related to diet, exercise, frailty, genetic factors and weight change could play a part.”
In an accompanying editorial, Deborah Gustafson, MS, PhD, of SUNY – Downstate Medical Center in New York, wrote that “considerations are needed in the assessment of the epidemiology of the association between BMI and late-onset dementia” which is common with late-life disorder.
“To understand the association between BMI and late-onset dementia should sober us as to the complexity of identifying risk and protective factors for dementia,” she wrote. “The report by Qizilbash and colleagues is not the final word on this controversial topic.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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