Dementia risk factors associated with cardiovascular health may have increased over time compared to factors such as smoking and having less education, finds a new study led by UCL researchers.
The study, published in The Lancet Public Health, explored how the prevalence of dementia risk factors had changed over time and how this could impact rates of dementia in the future.
It is estimated that there are currently 944,000 people living with dementia in the UK and 52% of the UK public – 34.5 million – know someone who has been diagnosed with a form of the disease. It is one of the nation's biggest killers and has been the leading cause of death in women in the UK since 2011.
There has been increasing interest in potentially modifiable risk factors, as eliminating these could theoretically prevent around 40% of dementia cases, according to research led by UCL academics.
For the new study, the researchers analyzed 27 papers, involving people with dementia across the globe with data collected between 1947 and 2015, and the latest paper published in 2020. They extracted data from each paper about dementia risk factors and calculated what proportion of dementia cases were attributable to each one, over time.
Dementia usually develops because of a combination of genetic and environmental factors, including hypertension, obesity, diabetes, education and smoking.
The team found that having less education and smoking had become less common over time and was associated with a decline in rates of dementia. Rates of obesity and diabetes have increased over time, as has their contribution to dementia risk.
The greatest dementia risk factor remained as hypertension in most of the studies that were reviewed although it is worth noting proactive management of hypertension has also increased over time.
Cardiovascular risk factors may have contributed more to dementia risk over time, so these deserve more targeted action for future dementia prevention efforts.
Our results show that levels of education have increased over time in many higher income countries, meaning that this has become a less important dementia risk factor. Meanwhile, smoking levels have also declined in Europe and the USA as it has become less socially acceptable and more expensive.
These patterns suggest that population-level interventions could significantly impact the occurrence of dementia risk factors, and governments should consider implementing schemes such as worldwide policies of education, and restrictions on smoking."
Dr. Naaheed Mukadam, lead author, UCL Psychiatry
This study was funded by the National Institute for Health and Care Research (NIHR) Three Schools' Dementia Research Programme.
Study limitations
While reported levels of cardiovascular risk factors, in particular, may have increased over time, the proactive management of these conditions has also increased over time in many countries so the effect on dementia may be neutral or may contribute less risk to dementia over time.
Additionally, all studies analyzed in the new research were from 2015 and earlier so may not reflect how trends may have changed since that time.
Study links obstructive sleep apnea to increased dementia risk in women