The quality of evidence is downgraded by possible ecological bias, and by roughness in the classification of studies as primary or secondary preventive studies.
A Cochrane review [Abstract] 1 included 4 studies with a total of 8 912 subjects. Participants had mild hypertension defined as a systolic blood pressure (BP) of 140 - 159 mmHg or diastolic BP 90 - 99 mmHg, and no evidence of cardiovascular disease at baseline. Mean age of participants in the included studies varied from 37.5 to 72 years. Treatment for 4 to 5 years with antihypertensive drugs as compared to placebo did not reduce total mortality (RR 0.85, 95% CI 0.63 to 1.15; 4 studies, n=8 912). Furthermore, antihypertensive treatment did not significantly reduce total stroke (RR 0.51, 95% CI 0.24 to 1.08), total coronary heart disease (RR 1.12, 95% CI 0.80 to 1.57) or total cardiovascular events (RR 0.97, 95% CI 0.72 to 1.32; 3 studies, n=7 080). Withdrawals due to adverse effects were increased by drug therapy (RR 4.80, 95% CI 4.14 to 5.57; absolute risk increase 9%).
Comment: Included studies were primary prevention trials, but there was no data on total cardiovascular risk of the participants
A systematic review and meta-analysis 2 included 74 studies with a total of 306 273 subjects (39.9% women and 60.1% men; mean age 63.6 years). In primary prevention, BP-lowering treatment was associated with reduced risk for death (RR 0.93, 95% CI 0.87 to 1.00) and major cardiovascular events (RR 0.78, 95% CI 0.70 to 0.87) with baseline systolic blood pressure (SBP) ≥160 mmHg, and with baseline SBP from 140 to 159 mmHg (mortality: RR 0.87, 95% CI 0.75 to 1.00; major cardiovascular events: RR 0.88, 95% CI 0.80 to 0.96), but not when baseline BP was below 140 mmHg (mortality: RR 0.98, 95% CI 0.90 to 1.06; major cardiovascula events: RR 0.97, 95% CI 0.90 to 1.04).
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