Dec. 15 (UPI) -- Certain patterns of weight gain and loss -- and corresponding changes in body mass index, or BMI -- may help predict a person's risk of developing dementia, a new study suggests.
The findings appeared Thursday online in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.
Researchers followed 2,045 people, the offspring of original participants in the Framingham Heart Study, for 39 years, measuring their weight roughly every two to four years and comparing different weight patterns -- stable, gain or loss -- among those who did and didn't develop dementia.
Decreasing BMI trends were associated with a higher risk of developing dementia in late life, the scientists found.
Further analysis showed that a subgroup's pattern of initially increasing BMI followed by declining BMI, both occurring in midlife, appeared to be central to the link.
BMI is calculated by taking a person's weight in kilograms and dividing by the square of height in meters, with a BMI of 18.5 to 24.9 considered healthy. The measurement doesn't take into account fat distribution and where fat is stored.
The scientists from Boston University Chobanian & Avedisian School of Medicine, and Peking Union Medical College in China, underscored the importance of the findings, since previous studies that looked at weight trajectories didn't consider how patterns of weight gain, stability or loss might help signal approaching dementia.
The researchers said the study also illustrates that dementia develops over many years, likely across a person's entire lifespan, and is not necessarily inevitable.
Monitoring easy-to-notice risk indicators such as weight patterns might allow early intervention to change the disease's trajectory, they said.
"If you have been on a path of weight gain, but then start to have weight loss, it is something to look into as to why," Rhoda Au, the study's corresponding author and a professor of anatomy and neurobiology at Boston University, told UPI in an email.
Au noted the study does not fully account for intentional weight loss -- and its results should not be interpreted as encouraging people to continue gaining weight, "since research also indicates that being overweight in general puts a person at greater risk for dementia."
According to Au, "The issue this project was trying to address is that decline in weight loss, particularly later in life, has also been associated with higher risk of dementia. ... Since this is an observational study, we can note the association, but we don't know the reason for why this association exists."
Patterns of intentional versus unintentional weight loss are at play here, Au said, and the association "might be different if we could separate out who was purposefully trying to lose weight versus those who are losing weight because of illness or, say, cognitive impairment, that has changed their eating patterns/behaviors."
The bottom line is the new study's results don't override previous research findings that indicate being overweight overall puts one at higher risk for dementia, Au said.
Being overweight also leads to other health outcomes, like diabetes and hypertension, which are risk factors for dementia, she added.
"Although our data don't speak to this and actually can't speak to this, my interpretation of our findings is that if someone has been slowly gaining weight because that's what happens as one gets older," that's OK, she said. But if a person starts to lose weight for unintentional reasons, "it's something worth looking into to figure out why."
Au noted the study doesn't address yo-yo dieting. But the research team is looking at fluctuations in BMI and hopes to get that study published in 2023.
Yet, Au conceded that "BMI is probably not the best measure. We have done other studies looking at other measures of adiposity, with [waist-to-hip ratio] seeming to be a better measure than simple BMI."
She explained the scientists were unable to explore waist-to-hip ratio for this study, "because we didn't measure it longitudinally the way we have with BMI. A much better study would be to look at these better measures of adiposity."
Au said she did not expect these results from the study, but she was not surprised by finding different associations across different weight-loss patterns.
Mainstream scientific approaches "try to find a simple answer to explain the root cause for very complex disease states," she said, "So the reason we are pursuing these studies is to show people the answer is not that simple and likely not the same for everyone."