Does the white-coat effect in people of African and South Asian descent differ from that in White people of European origin? A systematic review and meta-analysis

Objective To assess whether the white-coat effect in people of African (Blacks) and South Asian descent differs from that of people of European origin (Whites), and if so, whether this explains demonstrated ethnic variations in blood pressure. Methods A systematic literature review was carried out using Medline 1966-2003, Embase 1980-2003, and citations from references. The meta-analysis was performed using the Cochrane review manager software (RevMan version 4.2; Oxford, UK). Results Eight studies were examined, four studies from the UK and four from the USA. The mean systolic and diastolic white-coat effect was similar in Blacks and Whites. The weighted mean difference in systolic white-coat effect was 0.31 confidence interval 95% (CI) = - 1.96, 2.57; P = 0.791 and in diastolic white-coat effect was 0.18 (95% Cl = - 1.70, 1.35; P = 0.82). Two studies reported on South Asians. Both systolic and diastolic white-coat effect was significantly lower in South Asians than in Whites; the weighted mean difference in systolic white-coat effect was - 8.90 (95% Cl = - 13.04, - 4.76; P < 0.0001) and in diastolic white-coat effect was - 4.66 (95% Cl = - 7.29, - 2.03; P < 0.0001). Conclusion The blood pressure differences between Blacks and Whites are unlikely to be a result of variations in white-coat effect. In contrast, the slightly lower clinic blood pressure in some South Asian populations such as Bangladeshis might be partly caused by a low white-coat effect but more studies are needed in this subject.