New research has found a possible connection between rapid weight loss in older adults and a higher risk of developing dementia later in life. While the study does not confirm a cause-and-effect relationship, it raises important questions: Does weight loss contribute to dementia risk, or is it an early symptom of the condition?

Although weight loss is often a natural part of aging, experts say it doesn’t always signal cognitive decline. However, in some cases, weight loss may be an early indicator of underlying brain changes long before noticeable symptoms appear.

What the Research Found

The study, recently published in JAMA Network Open, investigated how cardiometabolic factors—such as obesity, blood pressure, diabetes, and cholesterol—might be early signals of dementia risk. Researchers tracked the health of older adults over 11 years, comparing those who later developed dementia with those who didn’t.

Participants who were eventually diagnosed with dementia had a faster and steeper decline in body mass index (BMI), starting many years before their diagnosis. These individuals also showed lower waist circumference and, interestingly, higher levels of HDL (“good”) cholesterol about five years before symptoms became evident.

According to the study authors, these results support the idea that metabolic changes and weight loss may occur in the early stages of dementia, even before cognitive symptoms become obvious.

A Closer Look at the Study

Cardiometabolic risk factors like uncontrolled diabetes and high blood pressure have long been associated with dementia. However, previous research on the topic was often limited by small sample sizes or data taken only from hospital records.

This new study used data from the ASPREE trial and its extension, covering adults aged 65 and older in the U.S. and Australia who were free from major cognitive impairments, disability, or cardiovascular disease at the start.

Out of nearly 5,400 participants, 1,078 developed dementia while 4,312 did not. The research team analyzed data including BMI, waist size, blood pressure, glucose, triglycerides, and cholesterol levels.

Across the board, BMI declined with age. But participants who developed dementia had lower baseline BMI and a more rapid decline starting at least a decade before their diagnosis. They also had lower waist circumference around ten years before diagnosis.

Interestingly, other health measures—like blood pressure, glucose, and LDL cholesterol—did not differ significantly between those who developed dementia and those who didn’t. However, people who were later diagnosed with dementia experienced a greater increase in HDL cholesterol levels about 4 to 11 years before diagnosis.

What’s the Link Between Weight Loss and Dementia?

At first glance, it may seem like losing weight increases dementia risk. But researchers believe it’s more likely that the early stages of dementia cause weight loss—a phenomenon known as reverse causation.

Experts explain that brain changes in early dementia can impact appetite, metabolism, and daily functioning. These changes might lead to unintentional weight loss because a person may forget to eat, have difficulty cooking, be less physically active, or experience social withdrawal.

The link between rising HDL levels and dementia is less clear. It could be the body’s reaction to early brain changes, but more research is needed to fully understand the connection.

It’s also unclear whether weight loss and HDL increase are risk factors that lead to dementia or early symptoms of the disease. Clarifying this distinction could help improve early diagnosis and intervention.

One limitation of the study is its lack of participant diversity. Over 95% of participants were white, making it difficult to know whether the findings apply broadly to other racial and ethnic groups—particularly communities that face a higher risk of both dementia and cardiometabolic conditions.

Should Older Adults Worry About Losing Weight?

The study found that people who later developed dementia lost weight more quickly, but all participants experienced weight loss over time—something that is common with aging.

While the pattern is noteworthy, researchers say it’s still difficult to separate normal age-related weight loss from early signs of dementia. More research is needed to understand this relationship in practical healthcare settings.

Weight loss alone is not a strong predictor of dementia. It should be assessed alongside other indicators such as cognitive tests, brain imaging, and biomarkers. Unintentional weight loss may also be caused by other health conditions unrelated to dementia.

That said, if someone is also experiencing signs like memory issues, changes in judgment, or difficulty with communication and daily tasks, it could be time to talk with a healthcare provider.

Experts recommend monitoring cognitive health when there are multiple potential signs—not just weight loss alone. If family members or the individual themselves notice changes, early evaluation can help lead to faster diagnosis and better treatment options.