A new study led by researchers at University College London shows that people with a higher body mass index (BMI) in midlife are more likely to develop dementia. The findings, based on data from 39 studies of long-term health, are published this week in the scientific journal Alzheimer’s and Dementia.
BMI is used to measure a person’s size relative to their height and is commonly used by doctors to help assess whether a person is healthy weight. In the UK a BMI score above 25 may indicate that a person is overweight, whereas a score of below 18.5 may suggest that a person is underweight.
Researchers in this study pooled BMI data from a total of 1,349,857 adults taking part in research studies in America, Europe and Asia. A total of 6,894 participants developed dementia in a period of up to 38 years from when their BMI was originally measured.
They found that the people who developed dementia tended to have a lower than average BMI in the two decades leading up to their diagnosis, but a higher than average BMI earlier in life.
Dr Rosa Sancho, Head of Research at Alzheimer’s Research UK, said:
“This large study links a higher BMI with an increased risk of dementia later in life and underlines the importance of maintaining a healthy weight to help support a healthy brain.
“While the researchers found that people with dementia actually tended to have a lower BMI in the years leading up to a diagnosis – this could be a consequence of the early stages of a disease like Alzheimer’s, rather than a factor affecting risk.
“We know that diseases that cause dementia get underway in the brain many years before symptoms start to show, so our lifestyle in midlife can have a particularly strong impact on our brain health in later life.
“While BMI can be a crude measure and not necessarily a good indication of our general health, limiting the amount of body fat we carry is important for a healthy body and a healthy brain.
“As well as maintaining a healthy weight, the best evidence suggests that staying mentally and physically active, not smoking, only drinking in moderation, eating a healthy diet, and keeping blood pressure and cholesterol in check can help us to keep our dementia risk as low as possible.”