TL;DR
Get everyday helpers delivered free with Prime
- Fast, free delivery on millions of items
- Prime Video, Amazon Music and more included
- Member-only deals all year
A study of 4,523 U.S. adults who developed dementia found that those who were overweight or obese at diagnosis had lower mortality risk than those in the normal-weight range. The researchers say the finding is an association, not evidence that gaining weight improves survival, and the cause remains unclear.
People who were overweight or obese when diagnosed with dementia had a lower risk of death than those in the normal-weight range, according to a study published in the Journal of Alzheimer’s Disease. The analysis followed 4,523 U.S. adults who developed dementia and found the association persisted after researchers adjusted for several health and demographic factors; it does not show that gaining weight would extend a patient’s life.
Researchers from Columbia University Mailman School of Public Health and NYU School of Global Public Health used data from the Health and Retirement Study, a nationally representative study of U.S. adults aged 51 and older. Participants entered the analysis without dementia and later developed the condition. The data covered 1998 to 2022, allowing the team to examine weight before diagnosis and survival afterward.
Compared with people in the normal-weight category, participants who were overweight, defined as a body mass index of 25 to 29.9, had a 16% lower mortality risk. The reported risk was 27% lower for people with class 1 obesity, with a BMI of 30 to 34.9, and 22% lower for those with class 2 or 3 obesity, a BMI of 35 or higher. The researchers said the associations remained after accounting for factors including chronic conditions, smoking and demographics.
The findings describe differences between groups, not a treatment effect. The study did not test whether changing someone’s weight after a dementia diagnosis alters survival. Its authors also examined possible sources of bias, including weight loss before diagnosis and the possibility that the analysis of people who developed dementia could distort associations. Their additional analyses did not indicate that the biases they assessed were major explanations for the result.
Weight May Help Inform Survival Estimates
The result may help clinicians and researchers interpret weight at the time of diagnosis as one part of a broader picture of health and survival. It also draws attention to nutrition in dementia care, where eating difficulties, appetite changes and weight loss can affect patients. The authors said a higher BMI could reflect greater energy reserves or muscle mass, but the study did not establish that either explains the survival difference.
The finding may seem at odds with evidence that obesity is associated with conditions such as heart disease and diabetes and that higher weight in midlife is linked to an increased chance of developing dementia later. Those questions concern different stages and outcomes: this study examined survival after dementia diagnosis, not the risk of developing dementia. It cannot be read as evidence that obesity is generally protective or that patients should try to gain weight.
For families and care teams, the practical point is limited but relevant: weight changes and difficulty eating deserve attention as part of care. The researchers frame BMI as a possible prognostic signal, not a recommendation or stand-alone forecast for an individual patient.
Popular right now
DeLonghi Rivelia Automatic Espresso Machine Bundle with Grinder and Frother, Beige
Dreame L40 Ultra Gen 2 Robot Vacuum and Mop
Vitamix Propel Series 750 Professional-Grade Blender, 4 Programs, Black
As an affiliate, we earn on qualifying purchases.
Why the Weight Finding Is Counterintuitive
Obesity is associated with increased risk for several chronic illnesses, and research has also linked overweight or obesity in midlife with a greater likelihood of later dementia. At the same time, some studies of people already diagnosed with dementia have reported better survival among those with higher weight. This difference between dementia risk and survival after diagnosis is the central reason the new analysis drew attention.
One concern is that weight loss can begin well before dementia is diagnosed. The source report notes earlier research by study authors Yuan Zhang and Virginia Chang indicating that weight loss may start up to a decade before diagnosis and accelerate closer to onset. A person classified as normal weight at diagnosis could therefore have previously weighed more, while weight loss could also be associated with advancing illness. The study used long-running data to track weight over time and assessed this and other possible biases.
The analysis included people who eventually developed dementia, so it cannot answer whether higher weight changes the chance of developing the condition. The authors also considered survivor bias: people with obesity may die earlier from other causes, leaving a comparatively healthier group who live long enough to develop dementia. Their analyses did not find that the examined biases accounted for the association, but the underlying reason remains unresolved.
“Our analyses suggest that the major sources of bias we examined do not explain the survival advantage associated with higher weight.”
— Yuan Zhang, corresponding author and assistant professor at Columbia Mailman School of Public Health
The Cause of Lower Mortality Remains Unknown
The study found an association but did not determine why higher BMI was linked to lower mortality. Greater energy reserves or muscle mass are possible explanations raised by the researchers, not proven mechanisms. The analysis also cannot show that intentionally increasing weight would improve survival, or identify what weight would be appropriate for any individual.
As with observational research, adjustments for measured factors cannot rule out every alternative explanation. The source report says the team examined several forms of bias and found they did not appear to account for the result; that does not settle the biological explanation. The findings also apply to the people and data included in this U.S. study, and do not by themselves establish how the association may differ among dementia types or patient groups.
Further Research Must Explain the Association
The study does not announce a clinical intervention or a change to dementia-care guidance. The next research step is to establish whether the association appears in other groups and to clarify how factors such as weight trajectories, nutrition and muscle mass relate to survival. Future studies could also examine whether different dementia conditions or stages produce different patterns.
For now, the authors say weight at diagnosis may offer useful prognostic information, while emphasizing that their analysis does not test weight gain as a strategy. Patients and caregivers should discuss nutrition and weight changes with qualified health professionals, who can consider the person’s full medical circumstances.
Key Questions
What did the study find?
Among 4,523 people who developed dementia, those who were overweight or obese at diagnosis had lower mortality risk than participants in the normal-weight range. The study reported risk differences of 16% for overweight, 27% for class 1 obesity and 22% for class 2 or 3 obesity.
Does the study show that gaining weight helps people with dementia live longer?
No. The researchers studied weight status and survival; they did not test whether gaining weight changes survival. The authors specifically cautioned that patients should not try to become overweight or obese based on these findings.
Why might higher weight be associated with longer survival?
The reason is unknown. The researchers suggested energy reserves or muscle mass as possible explanations, while noting that neither was established as the cause.
How was the study conducted?
The researchers analyzed Health and Retirement Study data collected from 1998 through 2022. The analysis included 4,523 U.S. adults who were dementia-free when they entered the study and later developed dementia.
What remains uncertain?
The study does not establish a causal effect, explain the biological mechanism or show whether the same association applies across different dementia types and patient groups. It also does not provide a weight-change recommendation.
Source: rss
