Sex ratio of multiple sclerosis in persons born from 1930 to 1979 and its relation to latitude in Norway

Abstract

A remarkable increase in female to male ratio of multiple sclerosis (MS) is recognised in high incidence areas. Norway is a high-risk area for MS, spanning latitudes 58-71 °N. We studied whether the sex ratio has changed over time and whether it differs by clinical phenotype or by latitude. Population-based epidemiological data and data from the Norwegian MS Registry on patients born from 1930 to 1979 were combined in this study. Place of birth was retrieved from the Norwegian Population Registry and information on clinical subtypes was obtained from the Norwegian MS Registry. The female to male ratio ranged from 1.7 to 2.7 (median 2.0) in 5,469 patients born in Norway, and increased slightly by 5-year blocks of year of birth (p = 0.043). The sex ratio was 2.6:1 in 825 patients born 1970-1979, which is significantly higher than in those born 1930-1969 (p < 0.001). In patients with relapsing remitting onset, the sex ratio was 2.4:1, while it was 1.1:1 in those with primary progressive disease. The sex ratio did not differ between the south, the middle and the north of the country. The overall sex ratio of MS is strongly determined by cases with relapsing remitting onset. We did not observe the remarkable increase in sex ratios of MS reported from other high-risk areas. The high sex ratio in the youngest birth cohorts may change as an increasing proportion of cases in this age group is being diagnosed. Sex ratio was not associated with latitude.

Risk of cancer among multiple sclerosis patients, siblings, and population controls: A prospective cohort study

“…In 2011, we conducted a sample of population-based epidemiological data on MS patients born between 1930 and 1979 in Norway retrieved from previously published population studies 23,24 and included cases not identified in the registries at the date for data extraction, as described in the previously published studies using the same cohort. 8,23,24 In addition, we included data from about 1200 patients with MS in a cohort enrolled in the Oslo Multiple Sclerosis Registry. 25 We retrieved the place of birth, sex and data on all of patients' unaffected siblings and their year of birth from the Norwegian Population Patients had been diagnosed with MS according to the criteria of Poser et al 26 or McDonald.…”

Sex‐Specific Differences in Life Span Brain Volumes in Multiple Sclerosis

“…The sex discrepancy favoring greater female MS prevalence has been slowly increasing over the 20th century 6 . Additionally, the female‐to‐male ratio has been largely driven by the youngest age groups, a category that is highly susceptible to lifestyle and hormonal changes 20 . A recent large cohort study that enrolled almost 16,000 definitive MS patients showed significant widening of the sex gap 21 .…”

Conclusion: National incidence and risk factor assessments may become a basis for the evaluation of prevention trials - prospects from the Third Nordic MS Symposium

“…Magyari reported from the Danish national MS register that incidence rates for women had increased from 4.61 to 11.85 during the period 1973–2002, while the incidence for men was essentially constant . A study from Norway reported an increase in female/male ratio of 1.7 from patients born 1930–1935 to 2.6 in those born 1970–1979, mainly determined by patients with a relapsing‐remitting onset . In contrast to these results, several reports from Sweden observed no change in the female/male prevalence ratio, including a short‐term (2001–2008) study by Ahlgren et al.…”