Excess Body Fat Associated with Dementia Risk
Researchers at the University of South Australia are warning that high levels of body fat can add to the risk of dementia and stroke.
Having examined grey brain matter from about 28 000 people, the reseachers’ study demonstrated that increased body fat incrementally leads to increased atrophy of grey matter in the brain, resulting in greater risk of declining brain health. Obesity is a major and growing issue worldwide; World Health Organization data shows that more than 1.9 billion adults are overweight, with 650 million being obese.
The lead researcher, Dr Anwar Mulugeta of UniSA, said the findings add to the growing number of issues known to be associated with being overweight or obese.
“Obesity is a genetically complex condition characterised by the excessive body fat,” Dr Mulugeta said. “Commonly linked to cardiovascular disease, type 2 diabetes, and chronic inflammation (a marker of dementia), obesity currently costs Australia’s economy about $8.6 billion dollars each year.
“While the disease burden of obesity has increased over the past five decades, the complex nature of the disease means that not all obese individuals are metabolically unhealthy, which makes it difficult to pinpoint who is at risk of associated diseases, and who is not.
“Certainly, being overweight generally increases your risk for cardiovascular disease, type 2 diabetes, and low-grade inflammation, but understanding the level of risk is important to better direct supports.
“In this study, we investigated the causal relationships of individuals within three metabolically different obesity types* – unfavourable, neutral and favourable – to establish whether specific weight groups were more at risk than others.”
These three obesity subtypes are:
- ‘unfavourable’ – people who tend to have fat around their lower torso and abdominal area. These people have a higher risk of type 2 diabetes and heart diseases.
- ‘favourable’ – people who have have wider hips but a lower risk of type 2 diabetes and heart diseases.
- ‘neutral’ – people who have relatively low or very low risk of the cardiometabolic diseases.
Dr Mulugeta continued, “Generally, the three obesity subtypes have a characteristic of higher body mass index, yet, each type varies in terms of body fat and visceral fat distribution, with a different risk of cardiometabolic diseases.
“We found that people with higher levels of obesity especially those with metabolically unfavourable and neutral adiposity subtypes had much lower levels of grey brain matter, indicating that these people may have compromised brain function which needed further investigation.
“However, we did not find conclusive evidence to link a specific obesity subtype with dementia or stroke. Instead, our study suggests the possible role of inflammation and metabolic abnormalities and how they can contribute to obesity and grey matter volume reduction.”
The study analysed the genetic data of up to 336 000 individual records in the UK Biobank, along with self-reported information and linked hospital and death register records to connect dementia and stroke.
It found that, in middle to elderly age groups (37-73), grey brain matter decreased by 0.3 percent for every extra 1 kg/m2, which is equivalent of an extra 3 kg of weight for persons of average height (173 cm).
Senior investigator Professor Elina Hyppönen, Director of UniSA’s Australian Centre for Precision Health based at SAHMRI, said keeping to a healthy weight is important for general public health.
“It is increasingly appreciated that obesity is a complex condition, and that especially excess fat which is located around the internal organs have particularly harmful effects on health,” Prof Hyppönen said.
“Here, we used the individuals’ genetic and metabolic profiles to confirm different types of obesity. In practice, our findings very much support the need to look at the type of obesity when assessing the type of likely health impact.
“Even in a relatively normal weight individual, excess weight around the abdominal area may be a cause of concern.”
Source: University of South Australia