Contributions
Abstract: 209
Type: Oral
Abstract Category: Clinical aspects of MS - 5 Epidemiology
Background: Incidence of multiple sclerosis (MS) has increased in the western world over several decades probably caused by increasing exposure to risk factors.
Objective: To analyse the development of the nationwide incidence rates of onset of MS in men and women, the sex ratios, and seasonality of birth in Denmark since 1950.
Methods: Since 1950 data on virtually all patients with onset of MS in Denmark have been kept in the Danish MS Registry, which is notified by all Danish departments of Neurology, MS clinics, MS rehabilitation hospitals, and the National Patient Registry. This has enabled monitoring of incidence of onset of MS in Denmark over six decades. Incidence rates were adjusted by direct standardization to the European Standard Population and calculated as number of new cases per 100,000 population per year. Seasonality of birth in MS patients was compared with the background population back to 1930.
Results: We have registered 19,378 cases with clinical onset of confirmed MS in Denmark from 1950 to 2009. From the 1950-1959- to the 2000-2009-onset period incidence more than doubled in women with an increase from 5.95 (95% CI: 5.63-6.28) to 12.12 (95% CI: 11.70-12.55) per 100,000 per year compared with a modest 24% increase in men from 4.49 (95% CI: 4.21-4.78) to 5.58 (95% CI: 5.30-5.87). The proportion of men with motor onset was almost stable at about 35% throughout the period, whereas it dropped a little in women from the 1980-1989-period to about 30-32%. The F:M sex ratio increased from 1.32 to 2.08, and the sex-ratio increased with increasing age at onset. Based on the 2000-2009-onset period, we estimated the cumulative lifetime risk of MS for both sexes at 0.65%, and the incidence of MS was 9.02 per 100,000 population years (95% CI 8.76-9.28). Age-period-cohort-analysis revealed a significant birth cohort effect. Contrasting to a number of other studies we found no seasonality of births in comparison with the background population, and a drop of births in November did not reach statistical significance.
Conclusion: The incidence of MS has doubled in women and only modestly increased in men over the last 60 years. The low increase of MS incidence in men indicates that better case ascertainment cannot account for the whole increase in women. Lifestyle changes in the female population that could include fewer childbirths, increased occurrence of obesity in childhood or youth, and increased cigarette consumption may play a role.
Disclosure: Dr. Magyari reports personal fees from Biogen Idec, grants and personal fees from Teva, personal fees from Merck, grants and personal fees from Novartis, grants and personal fees from Genzyme, grants from Roche.
Dr. Koch-Henriksen reports non-financial support from Biogen Idec, non-financial support from Novartis, non-financial support from TEVA.
Abstract: 209
Type: Oral
Abstract Category: Clinical aspects of MS - 5 Epidemiology
Background: Incidence of multiple sclerosis (MS) has increased in the western world over several decades probably caused by increasing exposure to risk factors.
Objective: To analyse the development of the nationwide incidence rates of onset of MS in men and women, the sex ratios, and seasonality of birth in Denmark since 1950.
Methods: Since 1950 data on virtually all patients with onset of MS in Denmark have been kept in the Danish MS Registry, which is notified by all Danish departments of Neurology, MS clinics, MS rehabilitation hospitals, and the National Patient Registry. This has enabled monitoring of incidence of onset of MS in Denmark over six decades. Incidence rates were adjusted by direct standardization to the European Standard Population and calculated as number of new cases per 100,000 population per year. Seasonality of birth in MS patients was compared with the background population back to 1930.
Results: We have registered 19,378 cases with clinical onset of confirmed MS in Denmark from 1950 to 2009. From the 1950-1959- to the 2000-2009-onset period incidence more than doubled in women with an increase from 5.95 (95% CI: 5.63-6.28) to 12.12 (95% CI: 11.70-12.55) per 100,000 per year compared with a modest 24% increase in men from 4.49 (95% CI: 4.21-4.78) to 5.58 (95% CI: 5.30-5.87). The proportion of men with motor onset was almost stable at about 35% throughout the period, whereas it dropped a little in women from the 1980-1989-period to about 30-32%. The F:M sex ratio increased from 1.32 to 2.08, and the sex-ratio increased with increasing age at onset. Based on the 2000-2009-onset period, we estimated the cumulative lifetime risk of MS for both sexes at 0.65%, and the incidence of MS was 9.02 per 100,000 population years (95% CI 8.76-9.28). Age-period-cohort-analysis revealed a significant birth cohort effect. Contrasting to a number of other studies we found no seasonality of births in comparison with the background population, and a drop of births in November did not reach statistical significance.
Conclusion: The incidence of MS has doubled in women and only modestly increased in men over the last 60 years. The low increase of MS incidence in men indicates that better case ascertainment cannot account for the whole increase in women. Lifestyle changes in the female population that could include fewer childbirths, increased occurrence of obesity in childhood or youth, and increased cigarette consumption may play a role.
Disclosure: Dr. Magyari reports personal fees from Biogen Idec, grants and personal fees from Teva, personal fees from Merck, grants and personal fees from Novartis, grants and personal fees from Genzyme, grants from Roche.
Dr. Koch-Henriksen reports non-financial support from Biogen Idec, non-financial support from Novartis, non-financial support from TEVA.