Racial Differences Affecting Night Time Blood Pressure Dipping Groups in Hypertensive Patients

BACKGROUND: Normal blood pressure (BP) follows a circadian rhythm, with dipping of BP at night. However, little has been done to show how the dipping groups vary amongst the White and Asian population at different periods of the year. This study aims to examine the pattern of nocturnal dipping between the White and Asian population, as well as to compare it to the different timings of the year, between summer and winter. METHODS: Ambulatory Blood Pressure Monitor recordings were obtained from 220 patients, half were White patients obtained from Mercy University Hospital, Cork, Ireland and half were Asian patients from National Heart Centre, Singapore during the summer period from May to June and the winter period from October to December. RESULTS: Both the Irish and Singaporeans exhibit a decrease in total number of reverse dipper from summer to winter. However, the redistribution of reverse dipper was mainly to the dippers in Singapore, while in Ireland it was to both the extreme dipper and dipper. Irish seasonal changes also resulted in an increase in nocturnal diastolic pressure (95% CI, 0.72 to 6.03, 3.37 mm Hg; p<0.05) and a change in the duration of dipping at night (95% CI, 0.045 to 1.01, 0.53 Hours; p<0.05). CONCLUSION: Regardless of race or temperature, reverse dippers seem to decrease in winter. However, the racial differences dictate the redistribution of the fall in number of dippers. This has implications on how reverse dippers should be treated at different periods of the year.