Extra weight was tied to faster memory decline over 24 years, hitting people over 65 hardest

A University of Georgia team followed more than 8,200 adults over age 50 for 24 years and found that higher body mass index went hand in hand with steeper losses in memory, overall cognition and executive function. Each one-point rise in BMI was associated with a faster rate of cognitive decline, and adults older than 65 showed the most pronounced effects. The analysis appeared in the Journal of Neurology in 2026.

Tech news worth reading: Get Techpresso, the daily email with the most interesting tech news and insights, read by 400,000+ professionals from Google, Apple and OpenAI.

Get Techpresso →

We may earn a commission if you sign up.

The result is an association drawn from observational data. It does not show that extra weight itself damages the brain, a limit that the researchers and outside scientists both acknowledge.

Twenty-four years of cumulative average BMI

Suhang Song, an assistant professor in the university’s College of Public Health, is the researcher the school credits with leading the work. The team analyzed a nationally representative study that tracked more than 8,200 adults over age 50 across 24 years, and it used cumulative average BMI, a running average of body mass index over the follow-up, as the exposure. The paper was published in the Journal of Neurology as “Association between cumulative average BMI and cognitive decline: a 24-year cohort study” in volume 273, issue 2. Neither the university release nor the ScienceDaily summary names the underlying cohort or describes how cognition was tested, so those details sit in the full paper.

Three areas of thinking were tracked: memory, executive function, which covers planning, organizing tasks and concentrating, and general cognitive function. Higher BMI over time was linked to declines faster than those typically seen in aging adults, and the association was strongest at the study’s eighth year. Obesity is defined as a BMI of 30 or higher. The public summaries give no hazard ratios, confidence intervals or p-values, so the size of the effect for each BMI point cannot be judged from them.

Reading the one-point figure takes some care. BMI is weight in kilograms divided by height in meters squared, so a single point amounts to roughly six or seven pounds for an adult of average height. The cumulative average design smooths out short-term swings such as a crash diet, which means the exposure reflects long-run weight rather than one weigh-in. It also means the analysis cannot separate an older adult’s current weight from decades of earlier weight, and the summaries do not say how the team handled that overlap.

The over-65 subgroup and the year-eight peak

Adults older than 65 showed the most pronounced effects, according to the University of Georgia release that announced the findings. Song said that if people managed their weight, they could significantly lower their rate of cognitive decline in just two years, and she described BMI as one of the most easily modifiable risk factors for aging well. Neither summary supplies a number behind the two-year claim, which reads as the lead author’s interpretation rather than a reported result.

Song also pointed out that there are no cures for dementia, which is why modifiable risk factors draw so much attention.

Proposed pathways and the limits of BMI

How extra weight might reach the brain is unsettled. The researchers point to inflammation, reduced blood flow and insulin resistance as likely routes without confirming any of them. Some scientists also say BMI alone is an incomplete measure of obesity because it ignores waist size and the weight-related conditions that a broader definition adds. By the CDC’s BMI-only definition, 41.9% of U.S. adults aged 20 and over had obesity in 2017 to March 2020, up from 30.5% in 1999 to 2000. The university release cites a broader definition that lifts the estimate to 75%.

Dementia gives the work its weight. The Alzheimer’s Association’s facts and figures put the number of Americans living with Alzheimer’s at more than 7 million, projected to reach nearly 13 million by 2050. Because the Georgia study is observational, it cannot exclude the possibility that early, undiagnosed cognitive change alters weight rather than the reverse, a reverse-causation problem common in long cohort research. The public summaries do not say whether the team tested for it.

The CDC page behind that percentage counts more than 100 million American adults with obesity and over 22 million with severe obesity, defined as a BMI of 40 or higher. Those totals show how many people sit on the exposure side of the Georgia analysis, even though the study itself reports changes in cognitive rate rather than absolute risk of dementia.

Age sharpens the demographic picture. The Alzheimer’s Association estimates 7.4 million Americans age 65 and older had the disease in 2026, and 74% of them were 75 or older. It also notes that every baby boomer will be 65 or older by 2030. A finding that is strongest in the over-65 group therefore lands on the fastest-growing slice of the population, which is one reason a modest per-point effect could matter at scale if it proves causal.

Gaps in the public summaries

Several details remain out of view: the cohort’s name, the memory tests, the covariates and the effect sizes. The ScienceDaily write-up of the university release repeats the main findings without them. Until the full paper is read, the safest summary is the one Song’s team supports, a 24-year pattern linking higher BMI to faster cognitive decline that is sharpest after age 65, with the causal chain still unproven.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

Tech news worth reading: Get Techpresso →

We may earn a commission if you sign up.