Extra weight in 60s may be linked to brain thinning years later

July 24, 2019

Science Daily/University of Miami Miller School of Medicine

Having a bigger waistline and a high body mass index (BMI) in your 60s may be linked with greater signs of brain aging years later, according to a study published by a leading University of Miami neurologist researcher in the July 24, 2019, online issue of Neurology®, the medical journal of the American Academy of Neurology. The study suggests that these factors may accelerate brain aging by at least a decade.

"People with bigger waists and higher BMI were more likely to have thinning in the cortex area of the brain, which implies that obesity is associated with reduced gray matter of the brain," said study author Tatjana Rundek, M.D., Ph.D., a UHealth neurologist, professor of neurology, epidemiology, and public health and scientific director of the Evelyn F. McKnight Brain Research Institute.

"These associations were especially strong in those who were younger than 65, which adds weight to the theory that having poor health indicators in mid-life may increase the risk for brain aging and problems with memory and thinking skills in later life," said Dr. Rundek,

The study involved 1,289 people with an average age of 64. Two-thirds of the participants were Latino. Participants' BMI and waist circumference were measured at the beginning of the study. An average of six years later, participants had MRI brain scans to measure the thickness of the cortex area of the brain, overall brain volume and other factors.

A total of 346 of the participants had a BMI of less than 25, which is considered normal weight; 571 people had a BMI of 25 to 30, which is considered overweight; and 372 people had a BMI of 30 or higher, which is considered obese.

For waist circumference, which can be different for men and women, the normal weight group, which was 54 percent women, had an average of 33 inches, the overweight group, which was 56 percent women, had an average of 36 inches, and the obese group, which was 73 percent women, had an average of 41 inches.

Having a higher BMI was associated with having a thinner cortex, even after researchers adjusted for other factors that could affect the cortex, such as high blood pressure, alcohol use and smoking. In overweight people, every unit increase in BMI was associated with a 0.098 millimeter (mm) thinner cortex and in obese people with a 0.207 mm thinner cortex. Having a thinner cortex has been tied to an increased risk of Alzheimer's disease.

Having a bigger waist was also associated with a thinner cortex after adjusting for other factors.

Rundek said, "In normal aging adults, the overall thinning rate of the cortical mantle is between 0.01 and 0.10 mm per decade, and our results would indicate that being overweight or obese may accelerate aging in the brain by at least a decade."

"These results are exciting because they raise the possibility that by losing weight, people may be able to stave off aging of their brains and potentially the memory and thinking problems that can come along with brain aging," Rundek said. "However, with the rising number of people globally who are overweight or obese and the difficulty many experience with losing weight, obviously this is a concern for public health in the future as these people age."

Rundek noted that the study does not prove that extra weight causes the cortex to get thinner; it only shows an association.

A limitation of the study was that, like many studies of older people, it is possible that the healthiest people are more likely to live longer and take part in studies, so that may affect the results. 

https://www.sciencedaily.com/releases/2019/07/190724161155.htm

Weight gain and loss may worsen dementia risk in older people

Study recommends continuous weight control and monitoring of weight changes to prevent dementia development

May 20, 2019

Science Daily/BMJ

Older people who experience significant weight gain or weight loss could be raising their risk of developing dementia, suggests a study from Korea.

Dementia is an important health problem especially with increasing life expectancy and an ageing population. In 2015, there were an estimated 46.8 million people diagnosed with dementia.

Meanwhile, the global prevalence of obesity, which is closely related to cardiometabolic diseases, has increased by more than 100% over the past four decades.

There is existing evidence of a possible association between cardiometabolic risk factors (such as high blood pressure, cholesterol and blood sugar levels) and dementia. However, the association between body mass index (BMI) in late-life and dementia risk remains unclear.

Therefore, a 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 Korean population.

They examined 67,219 participants aged 60-79 years who underwent BMI measurement in 2002-2003 and 2004-2005 as part of the National Health Insurance Service-Health Screening Cohort in the country.

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 (2004-2005) 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 totaled 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.

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.

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.

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.

This is an observational study, so can't establish cause, and the researchers point to some limitations, including uncertainty around the accuracy of the definition of dementia and reliance on people's self-reported lifestyle habits, which may not be accurate.

However, the study included a large amount of data and reported various modifiable risk factors of dementia in late life.

As such, the researchers conclude: "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.

"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."

https://www.sciencedaily.com/releases/2019/05/190520190053.htm