Prevalence of dysphagia in multiple sclerosis: a systematic review and meta-analysis

Although dysphagia was recognized as a clinical finding in multiple sclerosis (MS) as early as 1877, it has not received enough attention yet. With the progress of diagnostic method for dysphagia, there has been a rapid development in estimating the prevalence of deglutition disorder in MS. In this review, we aimed to conduct a systematic review and meta-analysis of published literature to establish the prevalence of dysphagia in multiple sclerosis. We systematically searched Embase, PubMed databases and Cochrane library from 1980 to August 2014, supplemented by hand searching to identify relevant studies. We used random-effects model to calculate pooled prevalence. Potential sources of heterogeneity were explored using sensitivity test and subgroup analysis, meta-regression analysis. Of 198 retrieved articles, 15 eligible surveys with a total population of 4,510 met the criteria. Twelve studies provided an estimate based on subjective screening test, which proved substantial heterogeneity (Cochran's χ(2) significant at p < 0.0001; I(2) = 92.4 %, 95 % CI 31-42 %), with a combined prevalence estimate of 36 %. Four studies provided an estimate based on objective measurements (clinical or instrument tools), which were substantial heterogeneity (Cochran's χ(2) significant at p < 0.005; I(2) = 77 %, 95 % CI 67-94 %), with a pooled prevalence estimate of 81 %. A large heterogeneity still existed after conducting several subgroup analyses and sensitivity tests. The findings confirm that more than one-third of the multiple sclerosis patients are suffering from swallowing difficulties. Therefore, we should be careful to interpret the pooled estimate due to the substantial heterogeneity between studies.