PS-C19-10: SEASONAL VARIATION IN THE EFFECT OF ANTIHYPERTENSIVE TREATMENT WITH THE IRBESARTAN/HYDROCHLOROTHIAZIDE COMBINATION

Abstract

Objective: There is increasing awareness of seasonal variation in blood pressure. In the present analysis, we investigated seasonal variation in antihypertensive treatment effect of the irbesartan/hydrochlorothiazide combination in patients with stage 2 and 3 hypertension. Design and Methods: The study participants were hypertensive patients enrolled in a 12-week therapeutic study. Antihypertensive treatment was initiated with the irbesartan/hydrochlorothiazide 150/12.5 mg/day, with the possible up-titration to 300/12.5 mg/day and 300/25 mg/day at 4 and 8 weeks of follow-up. The month of treatment commencement was classified as spring/summer (May to August) and autumn/winter (September to December). Results: Of the 501 enrolled patients, 313 and 188 commenced antihypertensive treatment in spring/summer and autumn/winter, respectively. The mean changes in systolic/diastolic blood pressure at 8 and 12 weeks of follow-up were greater in patients who commenced treatment in autumn/winter (-32.3/-16.5 and -34.2/-16.7 mmHg, respectively) than those in spring/summer (-28.4/-13.9 and -27.1/-12.8 mmHg, respectively), with a between-season difference of 3.9 (95% confidence interval [CI], 1.4–6.4, P = 0.002)/2.6 (95% CI, 0.9–4.2, P = 0.002) mmHg and 7.0 (95% CI, 4.7–9.3, P < 0.0001)/3.9 (95% CI, 2.4–5.4, P < 0.0001) mmHg, respectively. Further subgroup analyses showed a greater between-season difference in the changes in systolic blood pressure in patients aged 55 years and older (n = 255) than those < 55 years (n = 246, 12.6 vs. 6.9 mmHg, P = 0.02), and in patients with chronic kidney disease (n = 175) than those with normal renal function (n = 326, 12.1 vs. 7.4 mmHg, P = 0.06). Conclusions: There is indeed seasonality in antihypertensive treatment effect, with a greater blood pressure reduction in patients who commenced treatment in cold than warm seasons.