Changes in blood pressure among students attending Glasgow University between 1948 and 1968: analyses of cross sectional surveys Commentary: Changing population blood pressure levels

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Abstract
Objectives: To examine the changes in blood pressure over time in a cohort of young adults attending university between 1948 and 1968. Design: Cross sectional study. Setting: Glasgow University. Participants: 12 414 students aged 16-25 years—9248 men (mean age 19.9 years) and 3164 women (19.2 years)—who participated in health screening on entering university between 1948 and 1968. Main outcome measures: Systolic and diastolic blood pressure. Results: In male students mean systolic blood pressure adjusted for age decreased from 134.5 (95% confidence interval 133.8 to 135.2) mm Hg in those born before 1929 to 125.7 (125.0 to 126.3) mm Hg in those born after 1945, and diastolic blood pressure dropped from 80.3 (79.8 to 80.8) mm Hg to 74.7 (74.2 to 75.1) mm Hg. For female students the corresponding declines were from 129.0 (127.5 to 130.5) mm Hg to 120.6 (119.8 to 121.4) mm Hg and from 79.7 (78.7 to 80.6) mm Hg to 77.0 (76.5 to 77.5) mm Hg. Adjustment for potential confounding factors made little difference to these findings. The proportion of students with hypertension declined substantially in both sexes. Conclusions: Substantial declines in systolic and diastolic blood pressure over time were occurring up to 50 years ago in young adults who were not taking antihypertensive medication. Since blood pressure tracks into adult life, the results of the cross sectional comparisons suggest that factors acting in early life may be important in determining population risk of cardiovascular disease. Changes in such factors may have made important contributions to the decline in rates of cardiovascular diseases, particularly stroke, seen in developed countries during the past century. What is already known on this topic Mortality from stroke in developed countries decreased throughout the 20th century; declines in mortality from coronary heart disease occurred more recently Explanations may include favourable trends in risk factors, including blood pressure Since blood pressure tracks into adulthood, description of the trends occurring in blood pressure in young adults may help to elucidate the critical periods involved in influencing trends in blood pressure What this study adds Declines in blood pressure over time were taking place up to 50 years ago in young adults These changes did not result from use of antihypertensive medications and point to the importance of factors in early life in determining blood pressure and risk of subsequent cardiovascular disease