Multiple sclerosis frequency in Israel’s diverse populations

Background: Israel has served for almost half a century as a site for epidemiologic studies of multiple sclerosis (MS). Its small geographic size, well-equipped, accessible, and subsidized health facilities, trained physicians, detailed census data, and a National MS Register, maintained since 1960, offer advantages for accurate determinations of MS frequency in its diverse populations. Method: The authors calculated age-specific prevalence of MS in Israeli-born Jewish inhabitants, immigrant Jews from Europe/America and from North Africa/Asia, Israeli-born Christian and Moslem Arabs, Druze, and Bedouins. Results: Prevalence rate of MS per 10 population on June 30, 2000, for each of these groups in the order listed was 61.6, 53.7, and 27.9 for the Jewish groups and 35.3, 14.7, 10.9, and 17.3 for the non-Jewish groups. Three tiers in MS prevalence were apparent. The highest rates were in Israeli-born Jews and in Jewish immigrants from Europe/America (significantly higher in the former than the latter). Jewish immigrants from African/Asian countries and Christian Arabs had intermediate MS rates (significantly lower than in the first two groups but not significantly different from each other). Moslem Arabs, Druze, and Bedouins had the lowest rates of MS (significantly lower than in the intermediate group but not significantly different from each other). Conclusion: Diverse ethnic groups living in the same geographic area may have significantly different frequencies of MS. NEUROLOGY 2006;66:1061–1066 Geographic differences in the frequency of multiple sclerosis (MS) have been recognized for almost a century.1-3 Developed regions of the world, in general, show higher rates than developing regions, both in the northern and southern hemisphere.4 MS frequency may also differ in different ethnic groups living in the same area.5-14 Such differences in frequency have led to the conclusion that MS has a multifactorial etiology, including both genetic and environmental factors.15 However, although many hypotheses have been offered,15-25 the cause of MS has not yet been identified. Determination of MS frequency in different ethnic groups, all living in the same area, helps control for geoclimatic differences and may help identify the environmental risk factors that are most plausible for further study. We describe MS frequency in Israel, a small country with a Mediterranean climate and diverse populations. Israel’s population includes Jewish and nonJewish groups who have been living for centuries in Palestine. Additional Jews and non-Jewish groups immigrated after the State was established in 1948, increasing the total population 10-fold from about 650,000 at its founding to over 6 million at present.26 The groups who now live in Israel include the offspring of the indigenous Jewish groups, Moslem and Christian Arabs, Druze and Bedouins, Jewish immigrants from Europe and America, Jewish immigrants from North African, Middle Eastern, and other African/Asian/Pacific countries, among others. According to the national census at the end of 2000,26 61.8% of the Jews were native-born, 27.4% were European or American immigrants, and 10.8% were African or Asian immigrants; 81.8% of the Arabs and Druze were Moslem Arabs, 9.4% Christian Arabs, and 8.8% Druze. Non-Jewish immigrants came to Israel mainly from the surrounding Arab countries. All of these diverse groups constitute the Israeli population among whom we estimated MS prevalence. These groups provide opportunities to investigate the effect of environmental factors possibly related to risk of MS. Methods. Case ascertainment/data collection. This study was approved by the Helsinki Committee of Israel’s Department of Health (akin to an Internal Review Board in the United States). The Israeli National MS Register (INMSR) was established in 1960 by M. Alter with support from the NIH, the National MS Society in the United States, and Israeli Medical Centers. It is maintained by E. Kahana at the Uri Leibowitz Neuroepidemiology Unit, Hadassah Hebrew University Hospital, Jerusalem, Israel, with a duplicate dataset at Barzilai Medical Center, Ashkelon, Additional material related to this article can be found on the Neurology Web site. Go to www.neurology.org and scroll down the Table of