Weather-Related Changes in 24-Hour Blood Pressure Profile

Abstract

Abstract-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. Key Words: blood pressure monitoring, ambulatory Ⅲ hypertension Ⅲ aging S everal studies have reported that blood pressure (BP) values obtained both in the clinic and in ambulatory conditions are lower in hot than in cold months, which is also the case in a general population. 1 In summer, a reduction in cardiovascular mortality has also been observed, 2,3 with a reduction in the occurrence of stroke in hypertensive patients. 4,5 These findings might support the practice of downward titration of antihypertensive drug regimens, especially in the elderly. However, this clinical practice is not embodied in any of the guidelines. 6,7 Moreover, there is limited information regarding the effects of changes in daily mean outdoor air temperature (Ta) on ambulatory BP (ABP) in the elderly, in particular, in aged hypertensive subjects. Finally, no information is available on whether a clinic BP-guided reduction in the dosage of antihypertensive drug, in the case of hot weather, might be responsible for a reduced coverage of BP over 24 hours. The need to clarify these issues is underlined by the observation that older hypertensive patients do not show the same reduction in morbidity and mortality during hot months as younger subjects do. 3 The aim of the present study was, therefore, to more deeply investigate the climate-related changes in clinic and ABP and heart rate in subjects referred to our institutions for BP assessment during a 4-year period. This was done with special attention to the possible interaction between outdoor temperature-related BP changes, aging, and prescription of antihypertensive treatment. Methods

The risk of cold temperature: an important aspect of the determination of morning blood pressure surge

“…Second, previous studies have examined the association between cold temperature and BP levels and BP variability by assessing their absolute levels. 13,15,16 In contrast, the study by Murakami et al has revealed an association between the difference in outdoor temperature between the coldest and warmest days and the difference of prewaking morning BP increase between the coldest and warmest days. This point deserves to be mentioned, because a recent study demonstrated that an increased risk for CVDs in association with cold temperature was more relevant in the context of an unexpected temperature decrease than in terms of the absolute temperature level itself.…”

“…[13][14][15] This influence is not limited to office measurements but affects daily values (that is, home BP and ambulatory BP) as well. 15 Moreover, Modesti et al 16 recently examined the association between air temperature and ambulatory BP profile: they showed that cold temperature was significantly associated with excessive sleep-through MS in elderly persons, even when they were treated with a higher number of antihypertensive drugs in cold weather. This cold temperature-augmented morning BP increase may partly account for the increased number of CVDs on cold mornings during the winter season.…”

“…First, in contrast to previous reports 13,15,16 that examined the association between cold temperature and BP levels and BP variability using different subjects examined in different months of the year, the study by Murakami et al included a single group of subjects who were continuously examined by 24-h ambulatory BP monitoring for 7 days. Therefore, this study would seem to contain less noise in its analysis of the association between cold temperature effects and BP parameters.…”

Summertime dosage-dependent hypersensitivity to an angiotensin II receptor blocker

“…Although carried out on biased groups (members of different summer and winter populations that had been selected to attend hypertension clinics), ABP studies in Italy [2,3] found that, in summertime, night-time dipping was less evident and SBPs were slightly increased; it was only with day-time BP measurements that the summertime decrease was evident. The night-time SBP increase was particularly apparent in elderly subjects receiving antihypertensive medication (type not specified).…”

Summertime dosage-dependent hypersensitivity to an angiotensin II receptor blocker

“…Ambulatory blood pressure (ABP) recordings often reveal a small dip in BP values when subjects are resting at night (Fedecostante et al, 2012). In Italy, Modesti et al (2006) reported that in summer this night-time dipping was less evident, and systolic values (SBPs) were slightly increased; it was only with day-time BP measurements that the summer decrease was evident. They cautioned that 'the results of our study clearly indicate that the practice of reducing treatment in the summer in the elderly based on low clinic BP values is not good, because it might be responsible for a potentially dangerous increase in night BP.'…”