The global incidence of bullous pemphigoid: a systematic review and meta-analysis

Background Bullous pemphigoid (BP) is an autoimmune blistering disorder that mainly affects older people. Although the disease is associated with considerable morbidity and mortality, the burden of disease worldwide is unclear. Objectives The study aim is to pool the global incidence of BP and determine whether this varies according to geographic area, age group, setting and study quality. Methods Ovid MEDLINE, Ovid Embase and grey literature were systematically searched on 7 April 2020. Two reviewers independently screened, extracted data and appraised each study's quality using the Joanna Briggs Institute critical appraisal tool. Two domains, indicative of selection and survey bias, were used to identify high-quality studies. The cumulative incidence was standardized to 1 year and pooled in a random-effects meta-analysis. Subgroup and sensitivity analyses were conducted. Results Twenty-seven studies were identified, of which 23 provided cumulative incidence and four provided incidence rates. The cumulative incidence of BP was 8 center dot 2 [95% confidence interval (CI) 4 center dot 8-13.7] per million people whereas the incidence rate was 34 center dot 2 (95% CI 19 center dot 2-60 center dot 7) per million person-years. Of the continents that contributed more than one study, the cumulative incidence was 10 center dot 3 (95% CI 5 center dot 8-18 center dot 2) and 5 center dot 6 (95% CI 3 center dot 5-9 center dot 0) per million people in Europe and Asia, respectively. The incidence was highest in studies including adults only (n = 2), in population-based studies (n = 9) and in more recent years. The cumulative incidence was higher (13 center dot 3 per million people, 95% CI 6 center dot 0-29 center dot 5) when restricting the analysis to higher-quality studies (n = 11). High heterogeneity (I-2 > 82%) was observed across all pooled estimates. Conclusions The incidence of BP varies globally, is generally low but appears to be increasing over time. The burden of disease is likely to be underestimated.