Within-person variability in diastolic blood pressure for a cohort of normotensives

A random sample of 7500 inner-city Baltimore residents was screened for hypertension in their homes during 1973-1974. Three years later 2667 of those found to be normotensive at baseline were re-examined at home. Those with diastolic blood pressure ≥95 mmHg or who had begun taking antihypertensive medication since baseline were invited to a clinic for further evaluation. A sample of those whose baseline diastolic blood pressure was < 80 mmHg and whose follow-up was < 80 mmHg were also invited to the clinic. The within-person standard deviation was 7.8 mmHg for the baseline and follow-up home examinations. The between-occasion standard deviation was 7.4 mmHg and the within-occasion standard deviation was 2.4 mmHg. The between-occasion standard deviation was slightly lower for the 1976-1977 home and clinic examination but the within-occasion standard deviation was about the same. A small systematic decrease was noted between readings on the same occasion.