SEASONAL-VARIATION OF BLOOD-PRESSURE AND ITS RELATIONSHIP TO AMBIENT-TEMPERATURE IN AN ELDERLY POPULATION

Objective: To measure the magnitude and timing of seasonal variation o f blood pressure and related factors in the elderly living in the comm unity, and to assess their potential impact on cardiovascular risk. De sign: Prospective study; from January 1991 to February 1992 blood pres sure and other variables were measured at 2-monthly intervals in each subject in their own homes. Subjects: Ninety-six men and women, age ra nge 65-74 years, recruited from a single group general practice in Cam bridge. Main outcome measures: Seasonal variation of blood pressure, s easonal variation of prevalence of hypertension, seasonal variation of ambient temperature and body mass index. Results: Both systolic (SBP) and diastolic blood pressure (DBP) were greatest during the winter ac ross the whole distribution of blood pressure. There was a fourfold in crease in the proportion of subjects with blood pressures > 160/90 mmH g in winter compared with in summer. Regression analysis revealed high ly significant seasonal differences in both SBP and DBP. After adjustm ent for confounding seasonal effects, a 1-degrees-C decrease in living -room temperature was associated with rises of 1.3 mmHg in SBP and 0.6 mmHg in DBP. Conclusions: Seasonal variation of blood pressure is hei ghtened in older adults and may partly explain the greater cardiovascu lar disease mortality of elderly subjects during the winter. The blood pressures of elderly people may be inversely related to the ambient t emperature. The public health implications of these findings deserve f urther investigation.