Multiple sclerosis epidemiology in Asia and Oceania; A systematic review and meta-analysis

BACKGROUND: Multiple sclerosis (MS) is an inflammatory demyelinating CNS disease and the most common neurological immune-mediated disorder. Due to its progressive format, it affects patients' quality of life (QoL) significantly. This study aimed to evaluate epidemiologic parameters of MS in the Asia and Oceania continents.

METHODS: A comprehensive literature search on October 1st, 2020, was performed in PubMed, Scopus, and Web of Science to retrieve original population-based studies on MS epidemiology in the Asian and Oceanian countries, published between January 1st, 1985 and October 1st, 2020. The designed search strategy was repeated for each country, and the relevant referenced articles were added to our database. A random-effect model was used to combine the epidemiological estimates, and subgroup analysis was also performed by continent, region, and country, when possible. Meta-regression analysis was done to evaluate the effects of Human Developmental Index (HDI), latitude, and study period on the epidemiologic parameters.

RESULTS: A total of 3,109 publications were found, of which 89 articles met the eligibility criteria and were included for data extraction. These articles provided data on prevalence, incidence, and mean age at disease onset in 18 countries in Asia and Oceania, including Iran, Turkey, Cyprus, Kuwait, Saudi Arabia, Qatar, UAE, Jordan, Israel, India, Malaysia, China, Hong Kong, Taiwan, Republic of Korea, Japan, Australia, and New Zealand. The pooled total prevalence, incidence, and mean age of onset in Asia and Oceania were 37.89/100000 (95% CI: 35.65 - 40.142), 2.40/100000 (95% CI: 2.22 - 2.58), and 28.21 (95% CI: 27.55 - 28.88), respectively. MS prevalence and incidence in the female gender (68.7/100000 and 4.42/100000, respectively) were infinitely higher than in the male gender (24.52/100000 and 2.06/100000, respectively). Our subgroup analysis showed that MS was much more prevalent in Australia and West Asia among the studied area. The meta-regression showed that the total incidence decreased with an increase in the HDI, and the total prevalence in Asia increased with increasing latitude gradients. Also, the study period had a positive effect on the total prevalence and incidence in Asia and Oceania.

CONCLUSION: MS prevalence and incidence have increased in recent decades. This study highlights the need for further studies to elucidate MS's geographical and temporal variations' exact etiologies.