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NEWS DEMENTIA PREVENTION The nine modifiable risk factors that can help stave off cognitive decline By DR. ROBERT STRANG Chief Medical Officer of Health, Department of Health and Wellness T here is a long-standing, now known to be incor- rect, belief that dementia is a natural consequence of aging. In 2015, The Lancet launched a commission to review the available evidence on the prevention and manage- ment of dementia. The findings were published in 2017. 1 The findings indicate demen- tia is likely to be a clinically silent disorder that begins at mid-life, in which the terminal stages manifest as symptoms of dementia. This suggests there are prevention opportunities; the commission identified nine modifiable risk factors. The preventability of dementia is based on the concept of cognitive reserve: Individuals and populations with greater cognitive reserve, either through enhancing capacity or limiting its reduction, can withstand more neuropathology before developing cognitive or func- tional decline. Collectively, elimination of these risk factors could prevent up to one-third of dementia cases. Even a more modest reduction in dementia incidence through risk factor modification would have a substantial benefit to individuals, families, and health and social systems. The modifiable risk factors include the following: Education – Less time in education (none or only primary school), is thought to increase vulnerability to cogni- tive decline because it results in a lower cognitive reserve. It is not yet known if post-secondary education adds additional protection. Hearing loss – Recognition that even mild peripheral hear- ing loss increases the risk of cognitive decline is relatively new; it is not clear if this risk comes from a direct effect on cognition or indirectly through increased social isolation. Mean age of hearing loss shown to increase this risk. The effect of hearing aids is not yet known. Physical activity – Older adults who exercise are more likely to maintain cognition than those who do not exercise. Two meta-analyses, consisting of 31 observational studies, show that physical activity has a significant protective effect against cognitive decline, with higher levels of exercise being more protective. Smoking – Smoking dam- ages brain tissue through both cardiovascular effects and direct effects from neurotoxins in tobacco smoke, resulting in reduced cognitive reserve. Greater smoking history carries a greater dementia risk. Diabetes, hypertension and obesity – These three condi- tions are thought to increase the risk of dementia through car- diovascular effects. An increase in inflammation and high blood glucose could also be mecha- nisms by which diabetes impairs cognition. Depression – Cohort studies show a positive link between the number of depressive episodes and risk of dementia. It would also appear that this link only applies to depressive episodes occurring in the decade before dementia onset. It remains unclear whether depression is an early dementia symptom or a cause of dementia, but it is biologically plausible that it is causal. Social isolation – There is growing evidence that social isolation is a risk factor for dementia. This could be directly from social isolation leading to cognitive inactivity and indirectly from an increased risk of hypertension, cardiovascular disease and depression. Diet and alcohol use are likely modifiable risk factors for dementia, but there is insuf- ficient data at this time to be definitive. This information on modifi- able risk factors for dementia is important to include in initia- tives to improve overall health at both individual and popula- tion levels. Reference Livingston G et al. Dementia prevention, intervention and care. Lancet 2017;390: 2673-734 March 2018 | doctorsNS 17