A population-based study of the white-coat blood pressure effect: positive correlation with plasma cortisol.

We aimed to study the white-coat effect (WCE) of clinic blood pressure (BP) and its relation to plasma cortisol, neuropeptide Y (NPY) and demographic variables. Henry et al. have earlier suggested two stress-reaction patterns. The "defeat reaction" mainly involves the cortisol-axis and the "fight-flight-response" is mediated by the sympathoadrenal-system. Ninety-one men and 88 women 20-70 years of age, randomly selected from the population were recruited in this cross-sectional study. Clinic BP, plasma cortisol and plasma NPY (both analysed by radio-immunoassay) were obtained at 0800 h and 24h ambulatory BP (ABP) was performed. WCE was defined as supine clinic BP - mean daytime ABP. Cortisol correlated to the systolic WCE in the total material* (r = 0.22, p = 0.005) and in men 45-70 years of age (r = 0.45, p = 0.002, n = 47) and to diastolic WCE in women 45-70 years of age* (r = 0.37, p = 0.02, n = 38). (*women treated with oestrogens, or being pregnant, excluded, n = 21). Only in women did NPY correlate weakly to the systolic WCE (r = 0.22, p = 0.044). Subjects with one or more first degree hypertensive relative had a more marked systolic WCE than those without (-0.02 +/- 10 mmHg and -4.1 +/- 9.3 mmHg, respectively, p = 0.01). In conclusion cortisol correlated stronger to the WCE than did NPY. This would suggest the WCE to be a defeat reaction rather than a fight-flight-response.