Seasonal changes in orthostatic hypotension among elderly admitted patients.

Background And Aims: Orthostatic hypotension (OH) is a common finding among older patients. It has been shown that blood pressure (BP) is lower in summer than in winter. The aim of this study was to examine whether OH varies between seasons in the elderly population.

Methods: Five hundred and two inpatients (241 males, 261 females) of mean age 81.6 years were included in the study; 253 were studied in summer and 166 in winter. Orthostatic tests were performed 3 times daily, 30 minutes after meals. Orthostatic hypotension was defined as a decrease of at least 20 mmHg in systolic BP and/or 10 mmHg in diastolic BP upon assuming an upright posture at least twice during the day.

Results: OH was documented in 107 patients (34.8%). Initial BP did not differ between seasons (147.6 +/- 24.6 / 72.6 +/- 14.5 mmHg in summer, 146.7 +/- 23.4 / 71.5 +/- 13.4 mmHg in winter). However, the orthostatic drop in BP in the morning was greater in summer (-8.4 / -2.8 mmHg vs -4.3 / +0.2 mmHg in winter; p < 0.05). OH was also more prevalent in summer than in winter (37.9 vs 27.1%; p = 0.02). After adjustment for all confounders, the risk of experiencing OH in summer was 64% higher than in winter [adjusted odds ratio (OR) 1.64 [95% Confidence Interval (CI) 1.03-2.61].

Conclusions: The prevalence of OH is higher in summer than winter. Thus, more attention should be paid to the diagnosis of OH in summer.