Sex Differences in Ambulatory Blood Pressure Monitoring

Abstract 

Purpose

Referral to ambulatory blood pressure monitoring may have bearing upon blood pressure control and prognosis. We describe sex-related differences in referral for ambulatory monitoring and their prognostic impact.

Methods

Between 1991 and 2005, 3957 patients were monitored in our ambulatory monitoring service, of whom 2114 (53%) were women. Demographic and clinical data were analyzed according to sex.

Results

Age (58±15 vs 52±17 years, respectively) and body mass index (27.5±4.9 vs 26.9±4.0 kg/m², respectively) were higher in women than men. Treatment for hypertension was more prevalent in women (62% vs 53%, respectively). Clinic systolic blood pressure (148±24 vs 146±20 mm Hg, respectively) and clinic pulse pressure (65±22 vs 59±18 mm Hg, respectively) were higher in women compared with men. In women, the white-coat effect was increased, compared with men; 5.2±12.4% vs 1.5±10.7% systolic, and 5.4±11.2% vs 3.6±10.3% diastolic. Consequently, women had lower ambulatory blood pressure than men. In women, 24-hour blood pressure was 136±17/76±10 vs 140±15/81±10 mm Hg in men, awake blood pressure 141±17/80±11 vs 144±15/84±10 mm Hg, and sleep blood pressure was 125±19/67±10 vs 127±18/71±11 mm Hg. Age-adjusted ambulatory blood pressure also was lower in women. Ambulatory heart rate was higher in women (P <.0001). Kaplan-Meier survival did not differ by sex (P=.66), despite older age and higher clinic blood pressure.

Conclusions

The results might imply that referral was driven by the physicians' overall patient risk perception. The greater magnitude of white-coat effect in women, and correspondingly lower ambulatory blood pressure, might in part account for similar mortality in the face of older age and higher clinic blood pressure.

Keywords: Ambulatory blood pressure monitoring, Referral, Sex differences, White-coat effect, White-coat hypertension, Women's health