Changes in blood pressure in patients with hypertension receiving usual care in randomised controlled trials: findings from a systematic review and meta-analysis
The Problem On reviewing the evidence for allied health professional led interventions in the management of hypertension, we observed that blood pressure also falls within the usual care arms of included studies. Therefore we have undertaken further analysis to quantify the change in blood pressure in control arms of blood pressure intervention studies included in the review.
We used data from our Cochrane review (Allied health professional-led interventions for improving control of blood pressure in patients with hypertension - A115) that included 58 randomised controlled trials in 6897 patients identified in searches up to October 2013. This review included any nurse, pharmacist, or allied health professional-led intervention designed to improve control of blood pressure, compared to usual management of hypertension.We used the primary outcome of change in systolic and diastolic blood pressure from baseline to final follow up reported in usual care control arms of included trials. Changes in blood pressure were expressed as weighted mean differences pooled using generic inverse variance taking account of within patient correlations. Statistiical heterogeneity was assessed using the I2 statistic.
Mean systolic blood pressure fell by -3.9mmHg (95% CI: -5.5 to -2.4) and diastolic blood pressure fell by -2.7mmHg (-3.4 to -1.9) during usual care. Heterogeneity between studies was marked (systolic I2 = 97% and diastolic I2 = 94%). Usual care consisted of routine care only (45 trials) or enhancement with educational support for health professionals or patients (13 trials). Type of usual care did not account for observed heterogeneity, however restricting analyses to 24 high quality studies indicated a trend towards greater blood pressure reductions with enhanced usual care compared to routine care only: diastolic -4.6mmHg (-6.5 to -2.7) for enhanced vs. -1.9mmHg (-3.1 to -0.7; p=0.02) for routine care and systolic -6.9mmHg (-11.5 to -2.2) for enhanced vs. -4.2mmHg (-6.9 to -1.6; p=0.33) for routine care.
Statistically and clinically significant reductions in blood pressure were seen in the control arms of blood pressure intervention studies in this review, with greater reductions when usual care is enhanced within studies. Further work to establish whether this finding can be generalised to other blood pressure intervention studies is required. This trend should be considered when interpreting blood pressure intervention studies and in designing future interventions.
- Christopher Clark, East Somerset Research Consortium, West Coker, Somerset, UK
- Lindsay Smith, Department of General Practice, National University of Ireland, Galway, Ireland
- Liam Glynn, Department of Nursing, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, Canada
- Lyne Cloutier, School of Nursing, University of Southampton, Southampton, Hants, UK
- Olivia Clark
- Rod Taylor, East Somerset Research Consortium, West Coker, Somerset, UK
- John Campbell, East Somerset Research Consortium, West Coker, Somerset, UK