Dementia is a complex disorder and environmental and genetic influences interact to produce the disease. Causes of dementia include Alzheimer’s disease (AD), vascular dementia, mixed Alzheimer’s disease and vascular dementia, frontotemporal lobar degeneration, Parkinsons disease dementia and Lewy body dementia.
About 33.9 million people worldwide have AD, and prevalence is expected to triple over the next 40 years. One study published in 2010 found that delaying dementia onset by five years will reduce the 2040 prevalence by 37% and an onset delay of two years will reduce the prevalence by 16%.1
There is evidence on seven potentially modifiable risk factors for AD: diabetes, midlife hypertension, midlife obesity, smoking, depression, cognitive inactivity/low educational attainment, physical inactivity. Together, up to half of AD cases worldwide (17.2 million) and in the USA (2.9 million) are potentially attributable to these factors.
A 10–25% reduction in all seven risk factors could prevent as many as 1.1–3.0 million AD cases worldwide and 184,000–492,000 cases in the USA.2 AD incidence might also be reduced through improved access to education and use of effective methods targeted at reducing the prevalence of vascular risk factors.3
Delaying symptom onset by as little as one year could potentially lower AD prevalence by more than nine million cases over the next 40 years.
Studies to date suggest that a multifactorial intervention comprising regular exercise and healthy diet, along with the amelioration of vascular risk factors, psychosocial stress, and major depressive episodes, may be most promising for the prevention of cognitive decline. These strategies may show promise for the prevention of dementia at different stages of the disease.
Overall, evidence for preventing dementia is limited, and the exact role of these interventions warrants further examination by future studies.4
The strongest support from studies is seen for depression, (midlife) hypertension, physical inactivity, diabetes (midlife), obesity, hyperlipidemia and smoking. More research is needed for coronary heart disease, renal dysfunction, diet, and cognitive activity.5
Findings from the large, long-term, randomised controlled FINGER trial suggest that a multidomain intervention could improve or maintain cognitive functioning in at-risk elderly people from the general population.6
There is a growing consensus that the scientific evidence is now sufficient to justify policy action across the life course and for further research to reduce the modifiable risk factors and improve the population profile for recognised protective factors.7
In conclusion, prevention of dementia is now moving from observational to interventional studies to verify hypotheses and define tools that can be applied in the general population.
Since a cure for dementia is not yet available, finding effective preventive strategies is essential for a sustainable society in an ageing world.
Report based on a talk by Peter Passmore, Professor of Ageing and Geriatric Medicine, Queen’s University Belfast
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