Obesity in dementia was found to be associated with a low risk of death
Overweight and obesity are usually associated with an increased risk of various diseases, but after the development of dementia, another pattern is observed. A new study has shown that overweight people at the time of diagnosis may have a lower risk of death than normal-weight patients. About why weight turned out to be associated with survival in dementia, see the Izvestia article.
Why are extra pounds associated with lower mortality?
The researchers analyzed data from 4,523 people from the United States who did not have dementia at the time of inclusion in the study, but subsequently received such a diagnosis. For the analysis, information from 1998-2022 was used, which made it possible to estimate people's body weight immediately before diagnosis and life expectancy after it. The work was published in the Journal of Alzheimer's Disease (JAD).
Overweight people with a body mass index (BMI) of 25 to 29.9 had a 16% lower risk of death after developing dementia than normal—weight people. With first—degree obesity (BMI from 30 to 34.9), the indicator was lower by 27%, and with second— and third—degree obesity (BMI from 35) by 22%. These differences persisted after accounting for chronic diseases, smoking, and demographic characteristics.
However, the study does not show that being overweight or obese by themselves prolongs the lives of people with dementia. The authors studied the relationship between body weight at the time of diagnosis and subsequent mortality, rather than the effect of intentional weight changes on life expectancy.
Virginia Chang, associate professor of Social and Behavioral Sciences at New York University's School of Global Public Health and first author of the study
Our results show that weight can serve as a useful predictive signal for survival at the time of dementia diagnosis. They also support the idea that nutrition is a key factor in the health and survival of people with dementia.
How dementia can change body weight
One of the possible explanations for the result, the researchers consider changes in body weight that begin long before diagnosis. Previous work has shown that weight loss in people with developing dementia can begin about 10 years before diagnosis and accelerate in the years immediately preceding its establishment.
Because of this, a person of normal weight at the time of diagnosis could have already lost significant weight during the development of the disease. If only body weight was taken into account at one stage, such people could look like normal-weight patients, although weight loss was already associated with developing dementia and could be accompanied by a higher risk of death.
The researchers also tested other possible sources of bias, including the selection of people who later developed dementia and the so-called survivor error. Additional analysis did not show that these factors significantly explain the association found between a higher body weight and a lower risk of death.
What happens to the power supply
The authors consider several possible physiological explanations. One of them is due to the fact that people with a larger body weight may have more significant energy reserves. Another possible factor is a greater amount of muscle mass. However, none of these mechanisms has yet been confirmed as the cause of the discovered pattern.
In dementia, eating problems can occur due to changes in the central mechanisms that regulate appetite and initiative.
Virginia Chang
Nutrition can be a big problem for people with dementia. They may experience exhaustion and inability to eat, which may be due to changes in the central nervous system, leading to loss of appetite and initiative, increased energy expenditure, and difficulty eating on their own.
However, it remains unknown exactly why overweight and obesity at the time of diagnosis were associated with lower mortality. Therefore, the discovered pattern cannot be reduced to a single physiological mechanism.
What the study actually showed
Researchers believe that body weight at the time of diagnosis can be used as one of the indicators that help assess the prognosis for a person with dementia. At the same time, we are talking about prognostic information, and not about the proven benefits of being overweight.
The authors separately emphasize that the results do not mean that people with dementia should strive to be overweight or obese. The study was not intended to test this approach. Rather, the data obtained indicate the need to take into account the nutritional status and body weight changes when assessing the health of people with dementia.
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