Pattern of declining blood pressure across replicate population surveys of the WHO MONICA project, mid-1980s to mid-1990s, and the role of medication.

Objective: Declining mean systolic and diastolic blood pressures were observed in most populations of the World Health Organization MONICA (monitoring trends and determinants in cardiovascular disease) project from the mid-1980s to mid-1990s. We tested whether pooled results would show mean change associated with decline in high readings only, resulting from better antihypertensive medication, or with similar falls in low, middle, and high readings, implying other causes.

Design: Independent, random sample, cross sectional population surveys, each end of the MONICA decade.

Setting: 38 populations in 21 countries across four continents.

Participants: Design target in each survey of 200 participants in each 10 year age and sex group from age 35 to 64

Main Outcome Measures: Changes in the population in mean systolic and diastolic blood pressure, and in low, middle, and high readings-the 20th, 50th, and 80th centiles-and the differences between these changes.

Results: Individual populations differed considerably, but pooling the 38 population results gave mean changes in systolic blood pressure of -2.2 mm Hg in men, -3.3 mm Hg in women, and in diastolic blood pressure of -1.4 mm Hg in men and -2.2 mm Hg in women (overall average -2.26 mm Hg, population median -1.55 mm Hg). Antihypertensive medication, associated with high readings, rose by 0.5% to 11.4%. However, average falls in low and middle blood pressure readings were so similar to those in high readings and in the mean that no effect from improving treatment of hypertension was detected. Results in contrasted subgroups were consistent.

Conclusions: Blood pressure fell across 38 MONICA populations at all levels of readings, with no differential fall in high readings attributable to better control of hypertension. Despite the importance of medication to individuals, in that decade other determinants of blood pressure lowering must have been more pervasive and powerful in whole populations.