Association between bullous pemphigoid and hypertension: a systematic review and meta-analysis of observational studies

Studies have indicated a relationship between bullous pemphigoid (BP) and hypertension, but the findings remain controversial. To examine this association, we conducted a systematic review using studies from PubMed, EMBASE, Web of Science, and the Cochrane Library, applying a random-effects model while performing subgroup and sensitivity analyses to explore potential sources of heterogeneity. Subgroup analyses were performed by country, data source, and sample size. The quality of evidence was evaluated using the Newcastle-Ottawa Scale. The review protocol was registered in PROSPERO (ID: CRD42024573911). The analysis included 20 studies, primarily consisting of case-control studies from Europe and Asia, encompassing 72,981,822 participants, of whom 29,199 had BP. The mean ages of the BP group and the non-BP group were 74.62 and 74.25 years, respectively. Random-effects meta-analysis demonstrated a significant association between BP and hypertension (odds ratio [OR] = 1.13, 95% confidence interval [CI]: 1.07–1.20). Subgroup analyses revealed stronger associations in database studies (OR = 1.24, 95% CI: 1.17–1.31) and in studies with over 1000 BP cases (OR = 1.30, 95% CI: 1.23–1.37). No significant association was observed in studies conducted in Asia (OR = 1.05) or Europe (OR = 1.07). However, a significant relationship was found in studies from the United States (OR = 1.29, 95% CI: 1.12–1.48). This study found a significant correlation between BP and hypertension, particularly in the United States. However, as most included studies were observational in nature, causality cannot be inferred. Further research is needed to elucidate the underlying mechanisms and causal relationship between BP and hypertension.