The results in the present study indicated that having at least two of the five beneficial health factors reduced the risk of CVD mortality by 33% in adult men compared to those having no beneficial health factors. Furthermore, the risk of CVD mortality was reduced incrementally per increase in health profile score, and attaining all five beneficial health factors reduced the risk of CVD mortality by 67% in our sample of adult males. Our weighted analysis, which accounts for the five health factors having varying degree of importance, showed that a combination of moderate to high CRF, not currently smoking and being normal BMI is of high clinical importance (reduced the risk of CVD mortality by 69%).
These findings expand upon our earlier work which included 14,453 fewer participants (aged 30–79 years), with 643 fewer CVD deaths, over a shorter period of follow-up. This earlier study reported that there was a 45–77% risk reduction in CVD mortality among men with a health score ranging from 1 to 3 (high CRF, normal waist girth, and non-smoker), in comparison to men with a health score of zero.26
It should be noted that there was no plateau in the reduced risk between health profile scores of four and five (unweighted) or five and six (weighted), and it is unknown if further beneficial health factors considered in combination would continue to reduce the risk of CVD mortality. A plateau effect is likely at some point since beneficial exposures in adulthood alone would have to overcome genetic predispositions, potential epigenetic mechanisms associated with CVD34
, and exposures in utero6
, and during childhood or adolescence that have been linked to CVD in later life.3
Our results also complement previous studies, which found that increasing numbers of beneficial health factors in combination reduce the risk of early mortality or the incidence of chronic disease.15–17, 19–21
In addition, all of the previous studies have reported reduced risks of early mortality, or chronic disease incidence, per increase in health profile score, which aligns with our findings.15–17, 19–21
The strengths of associations reported do vary between studies, and a reason for this may be due to the different outcomes being investigated. Some adopt all-cause mortality or a cause-specific mortality, whereas others have adopted the incidence of a specific chronic disease as the dependent variable. Furthermore, each health profile score varies in terms of the health factors included and the definition of comparable health factors.
A recent study by Ford et al. found that out of 4 health factors (smoking status, BMI, physical activity and diet), never smoking and having a BMI <30 kg/m2
were especially important with regard to the incidence of chronic disease in general.35
We observed similar results from our weighted health score analysis, with CRF being additionally important with regard to CVD mortality. From a clinical standpoint, individuals should be counseled to achieve a health profile score of at least two and priority combinations of health factors should include moderate or high CRF, not smoking and normal BMI to protect against CVD mortality in men.
The major strengths of our study include the use of laboratory determined CRF as a health factor, the large number of participants, the prospective study design, and the extensive man-years of follow-up. No studies, other than our earlier work, have included CRF as a health factor. 26
This objective measure has been shown to be strongly, and independently, associated with reduced risk of CVD mortality.24, 25
As such, its inclusion as a health factor is important given the outcome variable. Nonetheless, there are limitations that need to be considered. Our sample comprised adult men, who were predominantly white and from high socio-economic backgrounds; this of course limits the generalizability of our findings only to such demographic groups, but strengthens the internal validity. Self-reported physical activity and alcohol consumption can be somewhat difficult to accurately recall, and there is a potential for social desirability that may lead to over-reporting of physical activity and under-reporting of alcohol consumed.36
Self-reported smoking status does not take into account the number of cigarettes smoked by past and present smokers. Each of the five health factors were given equal weight when determining the health-risk profile score, which does not take into account the possibility that the health factors may have a varying degrees of impact on CVD mortality. However, this most likely leads to a conservative effect size. Our health risk profile score was lacking a well measured dietary variable; however, the inclusion of an objective measure of CRF is unique to our study. Our health profile score was determined from five variables measured at a single point in time and did not take into account any change in these variables over time. Finally, residual confounding is likely as this was an observational study and such studies are unable to adjust for all known and unknown confounding variables.
In conclusion, there are multiple points throughout the lifetime where adverse exposures can contribute to the development of CVD. A health profile score of at least two can reduce the risk of CVD mortality in men, and moderate to high CRF, not smoking and normal weight are of most clinical importance to reduce the risk of CVD mortality.