MODELING THE ASSOCIATIONS OF BMI, PHYSICAL-ACTIVITY AND DIET WITH ARTERIAL BLOOD-PRESSURE - SOME RESULTS FROM THE ALLIED DUNBAR NATIONAL FITNESS SURVEY

In order to identify risk factors (e.g. physical inactivity, dietary c omposition) associated with blood pressure within a given population, it is necessary to adjust for differences in known associations (e.g. age, body weight) using a method such as the analysis of covariance. H owever, the blood pressure results from the Allied Dunbar National Fit ness Survey (ADNFS) were found to be non-linear with age, positively s kewed (with heteroscedastic errors) and therefore non-normally distrib uted. Hence, before valid inferences can be drawn from such data, ther e is a clear need to formulate an appropriate model for blood pressure that will overcome these undesirable characteristics. A multiplicativ e model (with allometric body size components) was proposed and fitted to the ADNFS blood pressure results. After a logarithmic transformati on the parsimonious solution was able to confirm the association with BMI, the non-linear changes with age, and overcome the heteroscedastic and positively skewed errors, i.e. the residuals from the fitted log- linear models for both systolic and diastolic blood pressure were symm etric and normally distributed. Other Factors were found to make a sig nificant additional contribution to the prediction of blood pressure. Cyclists, participants in vigorous physical activity and those subject s who consumed more fresh fruit, rice or pasta, and wine were found to have significantly lower mean levels of blood pressure. Indeed, the g ap in blood pressure between participants and non-participants in vigo rous physical activity increased further with age. However, subjects w ho drank more beer tended to have significantly higher mean levels of blood pressure. Thus, by developing an appropriate model for arterial blood pressure, some well known, and some less well known, association s with arterial blood pressure have been identified. The results sugge st that physical activity and other lifestyle factors may protect agai nst hypertension.