Prosperity has proven to be a double-edged sword for cardiovascular disease (CVD) prevention. While there has been undoubted progress over the last two decades in managing the clinical manifestations of CVD, rapid economic growth and urbanisation have also contributed to a rise in sedentary lifestyle and wider availability of energy-dense foods, key drivers of the obesity and type 2 diabetes pandemics. Indeed, some of the largest increases – not just in adults but also children and adolescents – have been in regions with rapidly growing economies, such as India and China (1). It therefore makes economic sense for renewed efforts in primary prevention strategies targeting the major modifiable cardiovascular risk factors to reduce the societal burden of CVD (2).
For all cardiovascular risk factors, what actually counts is both the level and duration of exposure. Therefore, the goal of CVD prevention should be to maintain optimal cardiovascular health long-term, by minimising the aggregate risk factor burden. This dictum is not new; over a decade ago, the Chicago Heart Association Detection Project in Industry (5) showed that middle-aged individuals with a favourable risk profile (including at least three of optimal blood pressure [≤120/80 mm Hg], total cholesterol [<200 mg/dL or <5.2 mmol/L], and body mass index [<25 kg/m2] and non-smoking) had lower lifetime risks for cardiovascular death and markedly longer survival (3). More recently, a meta-analysis of 18 cohort studies including 257,384 individuals confirmed the long-term benefits of optimal cardiovascular health. Individuals who maintained an optimal risk factor profile (total cholesterol <180 mg/dL or 4.7 mmol/L, blood pressure <120/80 mmHg, nonsmoking and nondiabetic status) from middle age had more than 10-fold lower lifetime risk of major coronary events (coronary heart disease death or myocardial infarction) and 2-fold lower risk of stroke than those with two or more risk factors (4). Maintenance of optimal cardiovascular health also reduces the subclinical atherosclerotic disease burden, in most but not all individuals, possibly reflecting uncertainty regarding ‘optimal’ levels for modifiable risk factors, as well as the role of nonmodifiable risk factors in determining propensity for CVD (5,6). There is also evidence that regaining optimal cardiovascular health in early adulthood has a beneficial impact on cardiometabolic risk (7). Thus, maintaining a healthy life style over many years will lead to gains in life quality and quantity.
The question is whether optimal cardiovascular health has implications beyond CVD prevention, given that the major cardiovascular risk factors, including high blood pressure, dyslipidaemia, obesity and diabetes, are also associated with deterioration in cognitive function in later life (8,9). To date, however, few studies have attempted to evaluate the impact of the combined risk factor burden on susceptibility to cognitive impairment and dementia in later life. A new French study provides important insights and support for promotion of optimal cardiovascular health to prevent the risk of dementia in later life (10).
About the Three-City Study
The Three-City Study (3C Study) is a population-based longitudinal study, initiated in 1999-2000, which is investigating the relation between vascular disease and dementia in individuals aged 65 years or more, selected from the electoral rolls of Bordeaux, Dijon, and Montpellier, France. Subjects without a history of CVD or dementia at baseline completed a through baseline assessment including information on sociodemographics, lifestyle, and health, medication use, a brief food frequency questionnaire, 15 leisure activities, neuropsychological testing, blood pressure and anthropometric measurements, and samples were collected for measurement of blood lipids, glucose and APOE genotyping.
The investigators used the 7-item tool (from the American Heart Association) (11) to evaluate cardiovascular health at baseline. Briefly, this tool assessed both health behaviours (relating to smoking status, body weight, physical activity, and diet) and biomarkers (untreated blood cholesterol, blood glucose, and blood pressure). Cardiovascular health level was defined two ways. First, the number of cardiovascular health measures at the recommended optimal level at baseline (i.e. nonsmoking, body mass index <25 kg/m2, regular physical activity, eating fish at least twice a week and fruit and vegetables at least 3 times a day, untreated cholesterol <200 mg/dL [5.2 mmol/L], fasting untreated glucose <100mg/dL, and blood pressure <120/80mmHg) was summed. Second, a global cardiovascular health score was used, in which individual metrics were assigned scores of 0, 1 or 2 for poor, intermediate or optimal levels, respectively, and then the scores of all metrics were summed. Subjects were followed every 2-3 years with face-to-face interviews and cognitive testing. The primary outcomes were incident dementia, validated by an expert committee, as well as the change in a composite score for global cognition.
The current report was based on data from 6,626 subjects (mean age 73.7 years; 63% women). Over a mean follow-up of 8.5 (maximum 16.6) years, 745 subjects developed incident dementia. In multivariate analyses, the risk of incident dementia decreased by 10% (hazard ratio 0.90, 95% confidence interval [CI], 0.84-0.97) with each additional health metric at optimal levels, and by 8% (hazard ratio 0.92, 95% CI, 0.89-0.96), for each additional point on the global cardiovascular health score. Additionally, an increasing number of health metrics at optimal level was associated with a lower rate of cognitive decline.
While the generalisability of results from the 3C study may be limited by the nature of the study cohort (predominantly urban-living and white), the findings have important implications for the wider benefits of promotion of cardiovascular health. The 3C study findings relate to older individuals; however, there is also emerging evidence that risk factor levels during childhood and their accumulation over time may detrimentally affect cognitive performance in middle age. For example, in the Young Finns Study (12), cumulative exposure to higher systolic blood pressure and total cholesterol from early life were associated with greater “cognitive aging” when compared with individuals with the lowest levels of these metrics. Taken together, these findings strengthen the case for a primordial prevention strategy from childhood, which undoubtedly would be cost-effective in a population health context (2).
The challenge is how best to achieve this, both in terms of public communication and education, as well as strategies to sustain lifestyle change. While empowering individuals to take responsibility for their long-term health is critical, maintaining cardiovascular health should not be a matter solely of willpower. Society also needs to play its part to ensure that adherence to healthy lifestyles from childhood is de rigueur and not optional.
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