Moderating Factors
Although individuals who are physically active or physically fit have a lower risk of developing hypertension, some of these individuals nonetheless will still become hypertensive. The vice versa, sedentary or unfit individuals not developing hypertension, may also occur. Underlying factors contributing to inter-individual variation in the effects of physical activity for preventing hypertension are still poorly understood. In recent years, some studies have sought to identify potential factors which may moderate this relationship.
Sarzynski and colleagues investigated the interaction between cardiorespiratory fitness and single nucleotide polymorphisms (SNPs) from seven hypertension candidate genes and their association with incident hypertension in the CARDIA study[43]. It was reported that cardiorespiratory fitness was associated with incident hypertension, however the SNPs tested did not modify this relationship. Thus, present data do not suggest a role for genetic factors in moderating the relationship between physical activity and the development of hypertension. Further research is still needed.
Using data from the Nurses’ Health Study I cohort, Cohen and colleagues investigated whether the relationship between physical activity and incident hypertension varied with age[44]. It was reported that the association between high levels of physical activity and the prevention of hypertension was weaker among older women when compared to younger women. However, because the incidence of hypertension is higher in older than in younger persons, increased physical activity would theoretically prevent a similar number of cases of hypertension in younger and older populations. Thus, investigators speculated that the overall public health benefit of lifestyle modification for the prevention of hypertension is similar for all ages.