Results of this study demonstrate a strong, graded relationship between maintenance of healthy lifestyles from young adulthood to middle age and the presence of the low CVD risk profile in middle age. Three-fourths of white and black women and over half of black and white men who adopted and maintained a healthy lifestyle with all five HLFs had a lower CVD risk profile after 20 years of follow up, when the average age was 45 years. Our results also indicate that for each sex and race group, as well as for the entire cohort and in all sensitivity analyses, people with a higher number of HLFs have a significantly higher prevalence of the low CVD risk profile, and vice versa. Moreover, among participants with a parental history of MI, the graded relationship between higher number of HLFs and presence of low CVD risk profile was consistent as well. These findings, which have significant public health implications, suggest that the low CVD risk profile in middle age can be achieved by adopting and maintaining a healthy lifestyle pattern early in adulthood.
Benefits of having the low CVD risk profile in middle age were first demonstrated by Stamler et al., utilizing 22-year follow-up data of the Chicago Heart Association Detection Project in Industry (CHA) and 16-year follow-up data of the Multiple Risk Factor Intervention Trial (MRFIT) Screenees Study.1
In both cohorts, mortality rates from coronary heart disease (CHD), CVD, and all causes in people with the low CVD risk profile were substantially lower than in others. Daviglus et al. analyzed Medicare data and reported that middle-aged participants with the low CVD risk profile in the CHA study had much lower rates of various chronic diseases at older ages.2
Morbidity rates decreased as the number of low CVD risk factors increased. More recently, Lloyd-Jones et al. used Framington Heart Study data to show that for those with the low CVD risk profile at age 50 the remaining lifetime risk of CVD was substantially lower than for people with two or more CVD risk factors.4
Furthermore, Capewell et al. estimated that if all U.S. adults had a low risk profile between 2000 and 2010, 372,000 (95%) fewer CHD deaths would have occurred in 2010.7
Benefits of the low CVD risk profile are not limited only to morbidity and mortality. Daviglus et al. showed in the CHA study that a low CVD risk profile in middle age was associated with significantly higher health related quality of life at older ages,2
and significantly lower Medicare charges, both average annual charges and those in the last year of life.5-6
Unfortunately, the prevalence of the low CVD risk profile is very low in the US population. In the CHA and MRFIT Screenees studies, baseline prevalence rates of the low risk profile range from 5 to 8%.1
In the recent report by Ford et al. using NHANES data, prevalence in the U.S. population was only 7.5%.9
However, as in our study, Ford et al. noted that prevalence is higher in younger age groups and declines dramatically with age. It has been unclear from these cross-sectional data whether the low risk profile can be achieved or maintained by adopting a healthy lifestyle.
In this study, five HLFs (never smoking, habitual moderate to vigorous physical activity, BMI<25 kg/m2
, modest or no alcohol drinking, and a healthy diet) were selected to address this question. The selection of these lifestyle factors was based on the study by Stampfer et. al, which clearly demonstrated that nurses with similar healthy lifestyle factors had much lower risk of coronary heart disease. In addition, Vita et al.28
demonstrated that people with low risk profile defined based on normal BMI, no cigarette smoking and vigorous exercise, had much lower risk for disability than others. The justification for inclusion of each of these is important. Obesity has been associated with high blood pressure and high serum cholesterol and is the major risk factor for metabolic syndrome and type 2 diabetes.29-30
Cigarette smoking has been established as the most important risk factor for lung cancer and is one of the major risk factors for CHD.31-32
Excessive alcohol consumption has been associated with hypertension, breast cancer and liver disease and mortality.33-36
The American Cancer Society and the American Heart Association recommend no or moderate alcohol consumption.37-38
Unfortunately in CARDIA, due to limitations of dietary data, we cannot directly define a healthy diet that is the same as the diet suggested by Stampfer et al.19
or as the DASH (Dietary Approaches to Stop Hypertension) diet. Instead, we used higher intake of potassium, calcium and fiber and lower saturated fat to define a healthy diet that is consistent with the DASH eating pattern. For example, high calcium intakes reflect higher intakes of dairy products, higher potassium and fiber intakes reflect higher fruit, vegetable and whole grain intakes, and lower saturated fat intakes reflect lower intake of red meat and butter. Habitual exercise has been shown to prevent CVD risk factors and CVD mortality and morbidity.39-41
In this study, pursuit of each of these HLF individually through young adulthood was significantly associated with the prevalence of low risk profile during middle age. We also performed a sensitivity analysis based on AHEI. The results are also similar.
Across the 4 race and sex groups, the prevalence of low risk profile in middle age in the group with all 5 HLFs were much higher than the prevalence in the 0-1 HLF group. Although a very high percentage of participants in the group with 5 HLFs attained low risk status in middle age, there were still approximately 40% who did not. Further, the attributable risk of not having low risk profile due to lack of 5 HLFs was 48%. These results are subject to some limitations. Diet, physical activity, alcohol and smoking data are self-reported and subject to measurement errors. Misclassification, if anything, may attenuate the associations with the low risk profile. Classifications of healthy diet and higher physical activity level were not based on well-established threshold levels but were selected relative to peers. In addition, due to lack of data, low sodium intake was not included as part of the healthy diet. For these reasons, the role of HLF on the low CVD risk profile is likely underestimated.
The finding that the prevalence of low risk profiles at Y20 tends to be lower in those who adopted HLFs but did not maintain them over time, as opposed to those who did not adopt HLFs at baseline but adopted and maintained them later, is important. It suggests that people will benefit from improving their lifestyle. However, people benefit the most if they can adopt and maintain a healthy lifestyle throughout the period from young adulthood to middle age. These data also suggest that genetic factors may not be very important in determining a low risk profile. For example, despite the attenuation of association due to misclassification, for those who had only 0-1 HLF, only 3% had a low risk profile at Y20; on the other hand, 61% of those who adopted and maintained 5 HLFs had low risk profiles. The prevalence of low risk profile increases as the number of HLFs increases. If genetic factors play an important role, we would expect to see a much higher prevalence of low risk profile with 0-1 HLFs. Likewise, our data showing the association of HLFs with low risk among those with a family history further support the notion that lifestyle may play a more prominent role than genetics.
Despite the steady decline of CVD mortality rates over the past forty years, it remains the number one killer in the United States.42
Recent data suggest a flattening of these downward mortality trends, particularly among younger adults ages 35 to 54 years, with evidence for an increase in CHD death rates among women 35 to 44 years of age. Such data suggest that the decades-long improvements in CVD mortality rates may be on the verge of reversing, perhaps as a result of the effects of the obesity epidemic in the US.43
As noted above, a large array of data indicate the potency of the low risk profile as a means for substantially avoiding CVD across the lifespan, and for improving healthy longevity. Recently, the American Heart Association announced its 2020 Strategic Impact Goal,8
with the aim of improving the cardiovascular health of all Americans by 20% by the year 2020. The low risk profile (termed “ideal cardiovascular health factors”) as well as many of the lifestyle factors (termed “ideal health behaviors”) studied in the present analysis form the cornerstone of the AHA’s new definition of cardiovascular health, and the number of these factors in middle age has been shown to be strongly, inversely associated with prospective CVD events.44
The recommendations of Healthy People 2020 use similar definitions and focus on improving cardiovascular health and its components. Clearly, a broad array of public health and public policy strategies involving schools, communities, state and governmental agencies, healthcare systems and private organizations will be needed to address the societal problems underlying the loss of the low risk profile from young adulthood to middle age. Such policies should be designed to improve the likelihood that individuals can make healthier choices regarding lifestyles that are associated with long-term improvements in healthy longevity and reductions in healthcare costs.8
In order to achieve these goals, it will be critical to implement public health and individualized approaches to drastically increase the prevalence of the low CVD risk profile in the population. To our knowledge, this is the first study to clearly demonstrate that the pattern of the low CVD risk profile (e.g., ideal levels of cardiovascular health factors, including blood pressure, cholesterol, fasting glucose and never smoking status) in middle age is strongly associated with practicing a healthy lifestyle in young adulthood and maintaining it into middle age. To accomplish the goal of expanding the prevalence of the low risk profile, more emphasis should be placed on primordial prevention by encouraging the adoption of healthy lifestyles from young ages.