Seasonal changes in blood pressure and frequency of related complications in elderly Israeli patients with essential hypertension.

BACKGROUND Earlier studies on hypertension demonstrated seasonal variations in different age groups. However, slightly greater fluctuations were found in the hypertensive elderly. OBJECTIVE We conducted a prospective 5-year study from January 1997 to December 2001 to evaluate the seasonal variation in blood pressure and the variables of age, gender, body mass index and related complications in elderly Israeli patients with essential hypertension. METHODS Blood pressure was measured in four seasons in 182 patients (98 men and 84 women; age range 65-91 years) treated for hypertension in our outpatient clinic. RESULTS Both systolic and diastolic mean blood pressures were higher during winter compared to summer (165 +/- 11.6 and 90 +/- 13.7 and 134 +/- 47.3 and 74 +/- 8.5 mm Hg, respectively; p < 0.001). There were no significant seasonal differences between spring and autumn or any correlation between the seasonal winter-summer difference in blood pressure and other studied parameters. Patients aged 65-75 years were unexpectedly more sensitive to winter-summer changes than older patients. There was a correlation between a large winter-summer difference in systolic blood pressure and a body mass index between 20 and 30, but there was none in lower or higher ranges. Supplementary antihypertension treatment was required during winter in 38% of these selected patients. Complications such as myocardial infarctions and strokes occurred twice as frequently in winter than in any other season (p < 0.0001). CONCLUSIONS Both systolic and diastolic blood pressures were highest during winter. Hypertension complications were more frequent in winter. Our results refute those of earlier studies that failed to find significant seasonal variations in blood pressure among the elderly.