Abstract
BackgroundNormal blood pressure (BP) follows a circadian rhythm, with dipping of BP at night. However, knowledge is limited in how the nocturnal dipping in hypertensive patients changes with the seasons. The study aims to examine the pattern of seasonal changes of nocturnal dip in an Irish population and furthermore, to compare it to the pattern observed near the equator where such seasonal variations are minimal, by also studying a Singaporean population. MethodsAmbulatory Blood Pressure Monitor recordings were obtained from 220 patients, half were from Mercy University Hospital, Cork, Ireland and half from the National Heart Centre, Singapore during the summer period from May to June and the winter period from October to December. ResultsIrish seasonal changes resulted in an increase in nocturnal dipping in the hypertensive patients, especially for diastolic pressure (95% CI, 0.72 to 6.03, 3.37mmHg; p<0.05) and a change in the duration of dipping at night (95% CI, 0.045 to 1.01, 0.53h; p<0.05). In Singapore, slight differences in dipping in systolic pressure were apparent despite the presence of only minor alterations in temperature (95% CI, 0.38 to 4.83, 2.61mmHg; P<0.05) or duration of daylight. ConclusionSeasonal changes not only affected the daily blood pressure but also the night time dipping status in hypertensive patients by mean value of 1.99mmHg and 3.38mmHg for systolic and diastolic pressure dip respectively. This has implications on how hypertensive patients should be treated during different seasons and when they are traveling to countries of different climatic environment.
Highlights
Various studies have demonstrated the presence of seasonal variations in blood pressure (BP) [1,2,3,4]
Seasonal changes affected the daily blood pressure and the night time dipping status in hypertensive patients by mean value of 1.99mmHg and 3.38mmHg for systolic and diastolic pressure dip respectively. This has implications on how hypertensive patients should be treated during different seasons and when they are traveling to countries of different climatic environment
This study aims to elucidate the seasonal pattern of nocturnal dipping in patients with a clinical diagnosis, or suspicion of hypertension
Summary
Various studies have demonstrated the presence of seasonal variations in BP [1,2,3,4]. Circadian variations have been demonstrated, where BP dips at night. Nocturnal dipping in BP is defined as the normal physiological change in the human body, which causes a 10–15% fall in BP at night time as compared to the day. This night time dipping is thought to be affected by an inability to excrete sodium during the daytime [6]. Night time dipping has been found to be greatly reduced in populations who are regularly exposed to seasonal changes [7]. The study aims to examine the pattern of seasonal changes of nocturnal dip in an Irish population and to compare it to the pattern observed near the equator where such seasonal variations are minimal, by studying a Singaporean population
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