People who have a high body mass index (BMI) are more likely to develop dementia than those with a normal weight, according to a new study.
Published in the Alzheimer’s & Dementia journal, the study analyzed data from 1.3 million adults living in the United States and Europe.
Researchers at University College London also found that people near the onset of dementia, who then go on to develop dementia, tend to have lower body weight than their dementia-free counterparts.
“The BMI-dementia association observed in longitudinal population studies, such as ours, is actually attributable to two processes,” said lead author Professor Mika Kivimäki.
“One is an adverse effect of excess body fat on dementia risk. The other is weight loss due to pre-clinical dementia. For this reason, people who develop dementia may have a higher-than-average body mass index some 20 years before dementia onset, but close to overt dementia have a lower BMI than those who remain healthy.”
“The new study confirms both the adverse effect of obesity, as well as weight loss caused by metabolic changes during the pre-dementia stage,” she noted.
Past research on how a person’s weight influences their risk of dementia has produced conflicting results, according to the researchers. Some findings have suggested that being obese poses a higher dementia risk, but other studies have linked lower weight to increased dementia incidence.
In this study, researchers from across Europe pooled data from 39 longitudinal population studies from the United States, the United Kingdom, France, Sweden and Finland. A total of 1,349,857 dementia-free adults participated in these studies and their weight and height were assessed. Dementia was ascertained using linkage to electronic health records obtained from hospitalization, prescribed medication and death registries.
According to the study’s findings, 6,894 participants developed dementia up to 38 years of follow-up.
Two decades before symptomatic dementia, higher BMI predicted dementia occurrence: Each five-unit increase in BMI was associated with a 16 percent to 33 percent higher risk of dementia. Five BMI units is equal to about 31 pounds for person who is five foot, seven inches tall.
In contrast, the mean level of BMI during pre-clinical stage close to dementia onset was lower compared to that in participants who remained healthy, researchers found.
This study’s findings suggests that maintaining a healthy weight could prevent, or at least delay, dementia, the researchers concluded.
Source: University College London