Ten-year legacy effects of baseline blood pressure 'treatment naivety' in the Second Australian National Blood Pressure study

Objectives: Current blood pressure (BP) management guidelines recommend that treatment thresholds for BP be based on absolute cardiovascular disease (CVD) risk rather than on elevated BP levels alone. Clinicians are concerned that delayed pharmacotherapy in individuals with high BP, but low CVD risk, may increase long-term CVD events. To investigate this, we examined differences in CVD events within the Second Australian National BP study (ANBP2) for those previously on pharmacotherapy and those who were not, as well as fatal events in the 6-year post-trial period.

Methods: Population consisted of ANBP2 participants without a prior CVD event. Adjusted Cox-regression hazard models were used to assess the effects of prior BP pharmacotherapy use on cardiovascular endpoints within ANBP2. An extended 6-year follow-up analysis for cardiovascular and all-cause mortality was also conducted.

Results: We found a higher in-trial CVD and all-cause mortality rate and incidence of new-onset diabetes for those on previous treatment versus those who were treatment-naive. We investigated whether this was an effect of the in-trial protocol, but this did not explain the observed differences. No difference in CVD or all-cause mortality at 10 years was observed between 'treatment-naive' and 'previous treatment' groups.

Conclusion: We found no long-term adverse mortality associated with treatment naivety of elevated BP in an elderly hypertensive cohort, but this finding is likely to be confounded as seen by the lower in-trial mortality in the 'treatment-naive' group. Legacy effects need to be explored in randomized trials of middle-aged populations where the clinical concern lies.