There’s a reason why doctors calculate body mass index (BMI) by measuring your weight and height at each visit: It’s one way to measure your health and determine if you may be at risk for certain health conditions like heart disease, diabetes, high blood pressure and certain cancers.
But changes in our BMI could also potentially indicate early signs of mild cognitive impairment (MCI) and even dementia, according to new research published in JAMA Psychiatry. Researchers specifically found that a rapid decline in BMI (and a significantly lower BMI due to that decline) occurred around seven years before a diagnosis of MCI.
“Our findings point to the BMI decline during the early stage of MCI, which could be utilized for early detection and prevention of MCI and dementia among older adults,” Jie Guo, PhD, lead author of the study at the Karolinska Institute in Stockholm, told Seasons.
Guo and her colleagues analyzed 1,390 “cognitively intact participants” who were a part of the Rush Memory and Aging Project, an ongoing study that measured BMI at baseline and conducted follow-ups and other neuropathological assessments from October 1997 to December 2020.
Of the participants analyzed, 39.5% developed MCI during the annual follow-up evaluations. Participants who developed MCI were older, had lower levels of alcohol consumption, had decreased BMI and were more likely to be carriers of the apolipoprotein E (APOE) 4 – a gene known to increase the risk of dementia – compared to those who remained cognitively intact after the follow-up.
Among the participants who developed MCI, 23.7% progressed to dementia. These patients were more likely to be older, have lower levels of physical activity and were also carriers of the APOE4 gene than those who were dementia-free.
In addition, Guo said in participants with mild cognitive impairment, BMI tended to decline earlier and faster compared to participants who remained cognitively intact.
“A faster decline in BMI and a lower BMI value may be an indicator of potential MCI and subsequent dementia,” she said.
What is BMI and how is it measured?
Body mass index is a measurement based on a person’s weight and height that can indicate “high body fatness” or the health of an individual. It is also used as a screening method for weight categories, including underweight, healthy weight, overweight and obesity.
You can easily calculate BMI using the BMI calculator below.
BMIs over 30 are considered obese, 25 to 29 are overweight, 18 to 24 is normal and under 18 is underweight.
Why might changes in BMI indicate signs of MCI and dementia?
According to Guo, the associations between BMI and MCI are still unclear; however, she hypothesizes that lower BMI is not a cause but a result of the underlying dementia. She said the changes in the brain may affect both a person’s sense of smell and appetite, which could then lead to weight loss. Also, lower BMI often means lower muscle mass, which may impact cognitive function “via muscle-brain cross-talk,” she said.
As people age, they may also occasionally forget to eat or to consume foods with proper nutrition, which can lead to medical issues and even memory loss. However, experts note more research is needed to better understand why changes in BMI could be an early indicator for MCI or dementia.
How closely should I monitor my BMI?
Guo recommends monitoring weight regularly as a way to identify and prevent health conditions along with cognitive impairment among older adults. While people can monitor BMI as well, experts say height is not as likely to fluctuate or change as much as weight.
If you notice any weight changes in yourself or your loved one, report those changes to your health care provider. From there, they can test for health comorbidities such as cancers and conduct screenings for conditions like MCI, dementia and Alzheimer’s disease.
“For older adults with abnormal BMI decline, we could screen their cognitive function to detect cognitive impairment earlier,” Guo said.
Furthermore, Guo said caregivers and adults could consider lifestyle modifications, improved dietary behaviors, increased physical activity and mental activities that may be helpful to improve or maintain cognitive function and prevent or delay the development of MCI and subsequent dementia.
What should I do if I notice any changes in weight or BMI?
What you do will depend on if the changes to your weight and BMI are intentional or unintentional. If BMI loss and weight change are intentional from improved dietary patterns or increased physical activity, Guo said there’s no need to see a doctor.
However, if these changes are not intentional, she suggests asking the doctor to help you figure out the potential reasons for these changes, such as underlying diseases related to the BMI change or treatments related to BMI loss. She also recommends screening for cognitive function using tests like the Mini-Mental State Examination.