Blood pressure changes over 7 years in a large workforce cohort in New Zealand

The aim of this study was to determine factors associated with changes in blood pressure levels over 7 years.

The baseline Workforce Diabetes Survey was carried out between 1988 and 1990 on workers predominantly aged =40 years, and a follow-up survey of 4053 participants was carried out between 1995 and 1997.

Overall, mean systolic and diastolic blood pressure levels increased by 6.0 (5.2%) and 3.1 (4.9%) mmHg, respectively, between the two surveys. The prevalence of GP-diagnosed raised blood pressure more than doubled over the 7 years--from 16.7% at baseline to 36.4% at follow-up. The two-thirds of participants whose blood pressure increased between the two surveys had on average lower baseline blood pressure levels, and were of shorter stature compared to those whose blood pressure levels showed no change or decreased (all p<0.05). A multivariate regression model of change in blood pressure over the 7 years showed that increase in systolic blood pressure levels was associated with lower baseline blood pressure levels; male gender; higher baseline weight and urinary albumin levels and greater increase in weight and urinary albumin levels over the 7 years; being of lower stature; being a never smoker; having newly or previously diagnosed diabetes; and being on current blood pressure lowering medication.

The principal modifiable factor associated with increasing blood pressure over the 7 years was higher baseline weight and a greater increase in weight during that time period. This study highlights the importance of prevention of weight gain as a key public health strategy and for managing raised blood pressure, which is one of the major determinants of the burden of CVD in New Zealand.