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Being overweight in mid-life may be linked to dementia risk

Being overweight in mid-life may be linked to dementia risk

People who are overweight when they are middle-aged may be at an increased risk of dementia in later life, according to a recent study. 121

A Swedish study looked at over 8,500 twins (identical and non-identical) who were aged 65 or older. During the course of the study, 350 people were diagnosed with dementia and 114 were found to have possible dementia.

The researchers found that the people who were overweight at middle age were 71 per cent more likely to develop dementia in later life than those who were a normal weight. This risk appeared to grow as weight increased — those who were obese in middle age were almost four times more likely to develop dementia compared to people at normal weight.

The study was carried out through a series of telephone interviews. The researchers collected information about each person’s current height and weight. Because the participants were part of a long-running study, they had already had their height and weight recorded when they were middle-aged (on average 43 years old). 

The researchers used this height and weight information to calculate each person’s body mass index (BMI). BMI is a commonly-used measure to standardise and define overweight and obesity in adults. The researchers classed people with a BMI of 25 to 30 as overweight, and those with a BMI of over 30 as obese.

They also collected other personal details, such as age, gender, whether or not participants had diabetes or diseases affecting the blood vessels (such as high blood pressure and high levels of cholesterol), and level of education. This information was important in the analysis of the results to ensure outside factors that may influence a person’s likelihood of developing dementia were taken into account.

During the telephone interview the researchers asked a series of questions to test each person’s mental ability, for example memory and reasoning skills. This test was used to indicate if the person could have dementia. If dementia was suspected, the person, along with their twin, was asked to have a full clinical assessment to determine whether they definitely had the condition, and if so, which type.

Dr Stan Goldstein, Medical Adviser, Bupa Australia, said: “This study adds to what we already know about certain possible risk factors for dementia. However, it had a number of limitations: key measures such as height and weight were self-reported; people who volunteered to take part in the study tended to be older, have less education and more were female, which affects how well this study’s participants reflect the population as a whole; and in analysis of the data, the researchers conclude that other factors than lifestyle factors such as overweight and obesity, may also have had an effect on the results. 

Still, this would be just one more reason that middle aged people should watch their weight and avoid the many conditions for which overweight and obesity are a risk.

“Reducing your energy intake by eating smaller portion sizes of healthy meals, and increasing energy use with regular exercise can help you to lose excess weight and improve your health in many ways. Maintaining a healthy weight reduces your risk of many common diseases, and it may also be beneficial in preventing dementia.”

Key facts about dementia

  • Dementia describes a failure of or significant decrease in brain functioning. It's a broad term for a range of symptoms, most notably memory loss, that result from damage to significant numbers of brain cells.
  • Dementia is more likely to affect people over the age of 65 – this is called late-onset dementia. Dementia occurring before this age is called early-onset. But dementia is not a normal part of ageing.
  • There are an estimated 270,000 people in Australia currently living with dementia and without a significant medical breakthrough, this is expected to soar to about 980,000 within forty years.
  • The causes of dementia aren’t well understood at the moment. However, certain things may mean you’re more likely to develop the condition, such as stroke and high blood pressure, or someone else in your family having it.

Read the study

Xu WL Atti AR Gatz M et al. Midlife overweight and obesity increase late-life dementia risk. A population-based twin study. Neurology. 2011; 76: 1568–74. Read the abstract here.