Background: Cardiovascular disease (CVD) is a major cause of mortality and morbidity. Traditional risk factors include systolic blood pressure, diabetes, adiposity, cholesterol and smoking. The prevalence and distribution of these risk factors in the population have changed within the last decades and CVD mortality rates have been declining. However, the impact of these changes on the contribution of the single risk factors to overall CVD risk remains to be investigated.
Hypothesis: We assessed the hypothesis that the population attributable risk (PAR) of traditional risk factors changes from 1985 to 2000.
Methods: The sample comprises N = 11 760 participants aged 30 - 65 years from four prospective population-based cohort studies enrolled in Southern Germany in 1985, 1990, 1995, and 2000. Participants were followed up for incident CVD events for ten years. We analyzed the traditional risk factors hypertension, defined as systolic blood pressure ≥ 140 mmHg or treatment with antihypertensive medication; diabetes mellitus; obesity, defined as a Body Mass Index ≥ 30 kg/m2; hypercholesterolemia, defined as total cholesterol levels ≥ 200 mg/dL; and smoking.
We calculated the PAR first according to Levin’s formula using both crude relative risks as well as adjusted hazard ratios and second as an average of all single sequential PARs according to the formulae by Ferguson.
Results: Temporal trends in prevalence varied for the respective risk factors. The prevalence of hypertension decreased slightly for women (from 25.0% in 1985 to 23.0% in 2000) and increased slightly for men (32.3% to 33.3%), whereas the prevalence of diabetes and obesity increased for both women and men. Prevalence of hypercholesterolemia decreased slightly for women (from 73.4% to 71.4%) and more pronounced for men (80.5% to 74.5%). Prevalence of smoking increased for women (20% to 23.6%), but decreased for men (36.4% to 32.4%). CVD events occurred in 2.4% of women in 1985 and 2.3% in 2000; for men, event rates were and 6.2% and 6.3%, respectively.
For both women and men the risk factor with the highest PAR in 1985 was hypertension (64.0% and 43.3%, respectively according to Levin’s formula). However, in 2000 the risk factor with the highest PAR was hypercholesterolemia (78.2% and 57.0%, respectively). The PAR for diabetes declined for women and increased for men. The PAR for smoking varied substantially between the studies without a discernible trend. According to Ferguson’s formulae, the PAR of all risk factors taken together increased from 74.3% to 84.2% in women and from 70.8% to 81.8% in men.
Conclusion: In conclusion, the CVD risk attributable to traditional risk factors has increased within the last decades. However, different methods of calculating the PAR have to be taken into account. These trends might influence public health policies focusing on the management of these risk factors in order to effectively prevent CVD.