Assessment of casual blood pressure variations.

All residents in a suburban community in southern Sweden, 8 years of age and older, were invited to an ophthalmological examination. The examination included a blood pressure determination. Of the 1917 persons invited 85·5% took part in the study. 3·5% of these were excluded because they were taking antihypertensive drugs. The investigations were conducted during 14 consecutive months and at different times of the day. The systolic and diastolic blood pressure distribution curves exhibited a positive skewing. The blood pressures rose to a plateau with essentially unchanged pressures in the age groups 28-32 years up to 38-42 years. In these ages, the systolic blood pressure was significantly higher among the males than among the females. The relation was reversed in the age groups above 48 years. The diastolic blood pressure showed no significant sex differences in the various age groups. A multiple linear regression analysis was used to determine whether there were diurnal and seasonal effects on the blood pressure independent of the age and sex. The systolic blood pressure during the winter months was 4·1 and 5·0 mmHg higher in the male and female subjects respectively, while the diastolic blood pressure during the winter months was 1·7 and 1·9 mmHg higher in the male and female subjects respectively. The time of day had no effect on the systolic blood pressure while the diastolic blood pressure increased by 0·24 and 0·27 mmHg/hr from 8 a.m. to 9 p.m. in the male and female subjects respectively. It is concluded that the small genuine effects of the time of measurement of casual blood pressure lack practical importance in screening of hypertension.