Why should population attributable fractions be periodically recalculated? : An example from cardiovascular risk estimation in southern Europe

ObjectiveTo determine the effect of age and study period on coronary heart disease (CHD) risk attributable to cardiovascular risk factors.MethodsA cohort of cardiovascular disease (CVD)-free randomly participants from Girona (Spain) aged 35–74 years recruited in 1995 and 2000 and followed for an average of 6.9 years. A survey conducted in the same area in 2005 was also used for the analysis. Smoking, hypertension, diabetes, sedentary lifestyle, obesity, total cholesterol ≥ 240 mg/dl, low-density lipoprotein (LDL) cholesterol ≥ 160 mg/dl, and high-density lipoprotein cholesterol < 40 mg/dl were the risk factors considered. The composite end-point included myocardial infarction, angina pectoris, and CHD death.ResultsLDL cholesterol had the highest potential for CHD prevention between 35 and 74 years [42% (95% Confidence Interval: 23,58)]. The age-stratified analysis showed that the population attributable risk (PAF) for smoking was 64% (30,80) in subjects < 55 years; for those ≥ 55 years, the PAF for hypertension was 34% (1,61). The decrease observed between 1995 and 2005 in the population's mean LDL cholesterol level reduced that PAF in all age groups.ConclusionOverall, LDL cholesterol levels had the highest potential for CHD prevention. Periodic PAF recalculation in different age groups may be required to adequately monitor population trends.