Background: Risk factors for raised blood pressure include obesity, physical inactivity, high dietary salt intake, stress, and high alcohol consumption. Much less is known about the effects on blood pressure of modification of these risk factors for the purposes of disease prevention. A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to estimate the effects of various non-pharmacological interventions on blood pressure.
Methods: RCTs of single interventions aimed at altering these risk factors among adults aged 45 or older with and without hypertension, and with at least six months follow-up were included. MEDLINE was the primary source and the boundaries of the study were from 1966 to April 1995.
Results: The majority of RCTs were of short duration and did not provide guidance on the sustainability of effects and were excluded. Totals of eight RCTs of salt restriction, eight RCTs of weight reduction, eight of stress management, eight of exercise, and one of alcohol reduction of longer than six months duration were found. Net (i.e. intervention - control group) systolic blood pressure changes, mean mm Hg (with 95 per cent confidence intervals in parentheses), in hypertensives were as follows: salt restriction -2.9 (-5.8,0.0), weight loss -5.2 (-8.3,-2.0), stress control -1.0 (-2.3,+0.3), and exercise -0.8 (-5.9,+4.2). Smaller changes were found in normotensive participants: salt restriction -1.3 (-2.7,+0.1), weight loss -2.8 (-3.9,-1.8), exercise -0.2 (-2.8,+2.4), and alcohol reduction -2.1 (-4.1,-0.1). Some interventions (e.g. stress control in normotensives) were not examined in either hypertensives or normotensives. The majority of RCTs were of low methodological quality and bias often tended to increase the changes observed. Few of the trials controlled for the confounding effects of concurrent changes in other blood pressure risk factors.
Conclusion: These net changes are probably overestimates of the effects that might be achieved by non-pharmacological interventions. There is a need for large-scale, long duration trials of these non-pharmacological interventions in both hypertensive patients and normotensive people to determine effect sizes more accurately.