Dementia is the greatest challenge for health and social care in this century. What can individuals and societies do to prevent dementia ?
The Lancet commission on Dementia reviewed this question in its report published this week in Lancet ( online , July 20). The word dementia has demeaning connotations and DSM has replaced it with the phrase ‘ major neuro cognitive disorders”. The present report uses the word dementia to cover all types of dementing disorders.
Dementia Decreasing? : Some countries have noticed an age specific decrease in dementia prevalence/ incidence. This is attributed to an increase in education. However, many societies would see increase in dementia due to increasing mid life rates of obesity and associated ill health.
We know that vascular / metabolic factors , diet, life style, education and mental health are the key modifiable risk factors here. However, the greatest risk factor, age is unmodifiable.
Cognitive reserve: Those with more brain reserve can tolerate more neuropathology without much cognitive and functional decline. At population level, access to reserve enhancing factors ( like physical exercise, intellectual stimulation, leisure activities ) over life span can reduce the risk of dementia. Hypertension can reduce the cognitive reserve and thus increase the risk of dementia. Cognitive resilience in later life is associated with healthier life styles, higher education and improved socio economic status during early childhood.
Population Attributable Risk
This review identified 9 modifiable risk factors. 35% of dementia is attributable to these factors. For example: We can see that if no one in above 65 age group is smoking, this will eliminate 5.5% of dementia in the population.
|Risk factor||Relative Risk (RR)||Pop. Attributable Factor (PAF) (Weighted)|
Factors 2, 3 and 4 are Midlife ( 45-65) risk factors . Factors 5,6,7,8,9 are later life risk factors. To see the PAF in perspective, you may want to see how much reduction in incidence of dementia will happen if apolipoprotein E4 allele is completely eliminated. This would bring 7% reduction at population level. If every one had good education (up to secondary level), this would bring the same population benefit.
One interesting finding is the risk due to hearing loss.The RR is highest for this factor. It is estimated that one third of all aged above 55 have some degree of hearing loss. Microvascular pathology may be a confounding factor here. Whether hearing corrections reduce this risk is not known at this moment.
What are the evidence based prevention strategies?
1.Treating hypertension is shown to reduce the risk of dementia
2.NSAID and statins do not reduce the risk. HRT is also not recommended for this benefit.
3. Mediterranean Diet: Possible positive effect . Reduce cognitive ageing.
4. Cognitive interventions: Engaging in cognitively stimulating activities can improve cognition and reduce dementia
5. Physical exercise improves cognition, but evidence to reduce dementia is lacking
6. Not much is known about the effect of social activities on risk reduction.
What about high risk group interventions?
The FINGER study was a mammoth undertaking to provide 4 intensive life style based interventions (diet, exercise, cognitive training, vascular management ) to 600 participants over 2 years. General cognition did improve , but there was no difference in memory when compared with controls. PreDIVA study ( Netherlands) showed that vascular risk factor management for elderly did not reduce the dementia incidence over 6 year period.
The current evidence base (from clinical trails) is unclear regarding specific interventions at population level that would reduce the dementia risk. Despite this, risk factor understanding is pointing towards the need to implement safe interventions that confer general health benefits. Increasing education in early life, increasing physical activity and social engagement, reducing smoking, treating hypertension , depression, diabetes, and hearing impairment should be our priorities.
Summary of the article
Livingston G, Sommerlad A, Orgeta V, Costafreda SG, Huntley J, Ames D, Ballard C, Banerjee S, Burns A, Cohen-Mansfield J, Cooper C, Fox N, Gitlin LN, Howard R, Kales HC, Larson EB, Ritchie K, Rockwood K, Sampson EL, Samus Q, Schneider LS, Selbæk G, Teri L, Mukadam N.
Lancet. 2017 Jul 19. pii: S0140-6736(17)31363-6. doi: 10.1016/S0140-6736(17)31363-6. [Epub ahead of print] Review
institute for mind and brain ( inmind hospital ), Thrissur, Kerala.