Researchers noted there was existing evidence of a possible association between dementia and cardiometabolic risk factors, such as high blood pressure, cholesterol and blood glucose levels.
“Both weight gain and weight loss may be significant risk factors associated with dementia”
However, they said that the association between body mass index in late-life and dementia risk was previously unclear.
Therefore, the team of researchers from the Republic of Korea set out to investigate the association between BMI changes over a two-year period and dementia in an elderly population.
They examined 67,219 participants aged 60–79 years who underwent BMI measurement in 2002-03 and 2004-05, as part of a national screening initiative.
At the start of the study period, characteristics were measured including BMI, socioeconomic status and cardiometabolic risk factors.
The difference between BMI at the start of the study period and at the next health screening (2004-05) was used to calculate the change in BMI.
After two years, the incidence of dementia was monitored for an average 5.3 years from 2008 to 2013.
During the 5.3 years of follow-up time, the numbers of men and women with dementia was 4,887 and 6,685, respectively.
Results showed that there appeared to be a significant association between late-life BMI changes and dementia in both sexes, according to the study published today in the journal BMJ Open.
Rapid weight change – a 10% or higher increase or decrease in BMI – over a two-year period was associated with a higher risk of dementia compared with a person with a stable BMI.
“People with early dementia can often report changes in appetite and diet”
However, the BMI at the start of the period was not associated with dementia incidence in either sex, with the exception of low body weight in men.
After breaking down the figures based on BMI at the start of the study period, the researchers found a similar association between BMI change and dementia in the normal weight subgroup, but the pattern of this association varied in other BMI ranges.
Cardiometabolic risk factors including pre-existing hypertension, congestive heart failure, diabetes and high fasting blood sugar were significant risk factors for dementia, they highlighted.
In particular, patients with high fasting blood sugar had a 1.6-fold higher risk of developing dementia compared to individuals with normal or pre-high fasting blood sugar.
In addition, unhealthy lifestyle habits such as smoking, frequent drinking and less physical activity in late life were also associated with dementia.
The researchers said: “Both weight gain and weight loss may be significant risk factors associated with dementia.
“This study revealed that severe weight gain, uncontrolled diabetes, smoking and less physical activity in late-life had a detrimental effect on dementia development,” they said.
“Our results suggest that continuous weight control, disease management and the maintenance of a healthy lifestyle are beneficial in the prevention of dementia, even in later life,” they added.
Dr James Pickett, head of research at the Alzheimer’s Society, said: “Understanding how lifestyle factors can contribute to dementia risk is crucial if we’re to find a way to prevent people developing the condition.
“Although this research suggests rapid changes to our weight later in life could increase dementia risk, it’s difficult to distinguish between cause and effect,” he said.
“People with early dementia can often report changes in appetite and diet,” he said. “Understanding how changes to our lifestyle throughout our lives may affect our risk of dementia is vital, which is why we’re funding the UK’s largest study focused on mid-life dementia risk factors.
But he added: “This study did confirm that heart disease and diabetes are risk factors for dementia.”