Dementia: modifiable risk factors
5 July 2023
Dementia is a syndrome characterized by nerve cells death and damage the brain, typically leading to deterioration in cognitive function. Crucially, the impairment in cognitive function is beyond what might be expected from the usual consequences of biological ageing. Moreover, it is commonly accompanied, and occasionally preceded, by changes in mood, emotional control, behavior, or motivation.
The number of older people, including those living with dementia, is rising, as life expectancy increases. Currently more than 55 million people have dementia worldwide, over 60% of whom live in low and middle-income countries. Dementia does not exclusively affect older people – young onset dementia accounts for up to 9% of cases. Every year, there are nearly 10 million new cases.
Dementia results from a variety of diseases and injuries that affect the brain. Alzheimer disease is the most common form of dementia and may contribute to 60–70% of cases. Dementia is currently the seventh leading cause of death and one of the major causes of disability and dependency among older people globally.
Critically, the number of people with dementia is rising: predictions about future trends in dementia prevalence vary depending on the underlying assumptions and geographical region, but generally suggest substantial increases in overall prevalence related to an ageing population. A growing body of evidence supports the 12 potentially modifiable risk factors for dementia modelled by the 2017 Lancet Commission on dementia prevention, intervention, and care:
- less education
- hearing impairment
- physical inactivity
- low social contact
- excessive alcohol consumption
- traumatic brain injury
- air pollution
Together these 12 modifiable risk factors account for around 40% of worldwide dementias, which consequently could theoretically be prevented or delayed. The potential for prevention is high and might be higher in low-income and middle-income countries where more dementias occur. Reduction of these risk factors might be protective for people with or without a genetic risk, although study findings have not been entirely consistent. Although we have more to learn about effectiveness, avoiding or delaying even a proportion of potentially modifiable dementias should be a national priority for all.
This new life-course model and evidence synthesis has paramount worldwide policy implications. It is never too early and never too late in the life course for dementia prevention.