Hot weather was independently associated with an increase in nighttime systolic blood pressure in treated elderly hypertensive subjects (P<0.02), despite lower 24-hour and daytime systolic pressures.
Observational (n=6,404)
Does outdoor air temperature affect 24-hour ambulatory blood pressure profiles in referred subjects?
Hot weather is associated with an increase in nighttime systolic blood pressure in treated elderly hypertensive subjects, suggesting a need for caution when reducing antihypertensive regimens in the summer.
p-value: p=<0.01
A downward titration of antihypertensive drug regimens in summertime is often performed on the basis of seasonal variations of clinic blood pressure (BP). However, little is known about the actual interaction between outdoor air temperature and the effects of antihypertensive treatment on ambulatory BP. The combined effects of aging, treatment, and daily mean temperature on clinic and ambulatory BP were investigated in 6404 subjects referred to our units between October 1999 and December 2003. Office and mean 24-hour systolic BP, as well as morning pressure surge, were significantly lower in hot (>90th percentiles of air temperature; 136±19, 130±14, and 33.3±16.1 mm Hg; P <0.05 for all), and higher in cold (<10th percentiles) days (141±12, 133±11, and 37.3±9.5 mm Hg; at least P <0.05 for all) when compared with intermediate days (138±18, 132±14, and 35.3±15.4 mm Hg). At regression analysis, 24-hour and daytime systolic pressure were inversely related to temperature ( P <0.01 for all). Conversely, nighttime systolic pressure was positively related to temperature ( P <0.02), with hot days being associated with higher nighttime pressure. Air temperature was identified as an independent predictor of nighttime systolic pressure increase in the group of elderly treated hypertensive subjects only. No significant relationship was found between air temperature and heart rate. Our results show for the first time that hot weather is associated with an increase in systolic pressure at night in treated elderly hypertensive subjects. This may be because of a nocturnal BP escape from the effects of a lighter summertime drug regimen and may have important implications for seasonal modulation of antihypertensive treatment.
Modesti et al. (Wed,) conducted a observational in Hypertension (n=6,404). Outdoor air temperature (hot vs cold days) vs. Intermediate temperature days was evaluated on 24-hour and daytime systolic pressure (p=<0.01). Hot weather was independently associated with an increase in nighttime systolic blood pressure in treated elderly hypertensive subjects (P<0.02), despite lower 24-hour and daytime systolic pressures.
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