Objective: To compare awake-sleep ambulatory blood pressure variation between Japanese-American and Caucasian women in Hawaii, specifically determining whether Japanese-Americans have reduced dipping of blood pressure during sleep, as is found in comparisons of Japanese and US samples.
Methods: Normotensive school teachers from East Hawaii who were either of Japanese-American (n = 70) or Caucasian (n = 48) ethnicity were recruited. They wore an ambulatory blood pressure monitor (Spacelabs 90207) that took measurements every 15 min during waking hours and every 30 min during sleep for a 24-h period on a normal workday. All subjects provided demographic information and underwent a series of anthropometric measurements the day before monitoring. Japanese-American subjects also answered questionnaires relating to cultural identity and migration history.
Results: The Japanese-American women had significantly higher mean diastolic (P < 0.01) blood pressure during sleep. These ethnic differences in sleep blood pressure persisted when analyses controlled for age, body mass index, and the waist-hip circumference ratio. There were also significant differences in the proportion by which blood pressure dipped from waking to sleeping, with the Japanese-American women dipping significantly less than the Caucasian women (P < 0.05 systolic, P < 0.001 diastolic).
Conclusions: Normotensive Japanese-American women have higher sleep pressure, and a smaller awake-sleep dip, in pressure than Caucasian women. The relative elevation of blood pressure in Japanese-American women during sleep, but not at other times of the day, is similar to the pattern seen among Japanese women in Japan.