Background
Evidence on long term effectiveness of public health strategies for lowering blood pressure
(BP) is scarce. In the Control of Blood Pressure and Risk Attenuation (COBRA) Trial, a 2 x 2
factorial, cluster randomized controlled trial, the combined home health education (HHE)
and trained general practitioner (GP) intervention delivered over 2 years was more effective
than no intervention (usual care) in lowering systolic BP among adults with hypertension in
urban Pakistan. However, it was not clear whether the effect would be sustained after the
cessation of intervention. We conducted 7 years follow-up inclusive of 5 years of post intervention
period of COBRA trial participants to assess the effectiveness of the interventions
on BP during extended follow-up.
Methods
A total of 1341 individuals 40 years or older with hypertension (systolic BP 140 mm Hg or
greater, diastolic BP 90 mm Hg or greater, or already receiving treatment) were followed by
trained research staff masked to randomization status. BP was measured thrice with a calibrated
automated device (Omron HEM-737 IntelliSense) in the sitting position after 5 minutes
of rest. BP measurements were repeated after two weeks. Generalized estimating
equations (GEE) were used to analyze the primary outcome of change in systolic BP from
baseline to 7- year follow-up. The multivariable model was adjusted for clustering, age at
baseline, sex, baseline systolic and diastolic BP, and presence of diabetes.
Findings
After 7 years of follow-up, systolic BP levels among those randomised to combined HHE
plus trained GP intervention were significantly lower (2.1 [4.1–0.1] mm Hg) compared to
those randomised to usual care, (P = 0.04). Participants receiving the combined intervention
compared to usual care had a greater reduction in LDL-cholesterol (2.7 [4.8 to 0.6]
mg/dl.
Conclusions
The benefit in systolic BP reduction observed in the original cohort assigned to the combined
intervention was attenuated but still evident at 7- year follow-up. These findings highlight
the potential for scaling-up simple strategies for cardiovascular risk reduction in lowand
middle- income countries.