New Study Finds Underweight People More Likely to Develop Dementia

Posted on April 11, 2015

A new study published in The Lancet Diabetes & Endocrinology journal associates being underweight in middle age with an increased likelihood of developing dementia. The study also found that people who are obese in middle age are less likely to develop dementia. The study analyzed the medical records of about two million people.

The study found that people who are underweight in middle age are a third (34%) more likely to be diagnosed with dementia than those of a healthy weight. The researchers found this increased risk persisted even 15 years after the underweight data was recorded.

The findings also show that middle-aged obese people are nearly 30% less likely to develop dementia than people of a healthy weight. This contradicted findings from some previous research. The researchers say obese means a person has a BMI greater than 30 kg/m2, which is body mass (in kilograms) divided by the square of your height in meters.

Dr. Nawab Qizilbash from OXON Epidemiology in London, UK and lead author of the study says in a statement, "If increased weight in mid-life is protective against dementia, the reasons for this inverse association are unclear at present. Many different issues related to diet, exercise, frailty, genetic factors, and weight change could play a part."

A report in the Washington Post suggests one possibility is that obese people "unknowingly take in dementia-fighting nutrients in the extra food they consume." It is also possible that some underweight people are starving their brains in some manner that causes damage. Starvation and extreme low-calorie diets are considered unhealthy. A study on the impact on the brain from severe dieting would be valuable.

The research paper on BMI and risk of dementia can be found here in The Lancet.