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Increasing female: male ratio in multiple sclerosis (MS) has been assigned to cohort effects, with females in more recent birth cohorts possibly being more exposed or vulnerable to environmental risk factors than males. We collected MS mortality data in Norway from 1951 to 2015 from The Norwegian Cause of Death registry. Age-Period-Cohort analysis was conducted using log-linear Poisson models, including sex interaction terms. MS was registered as the underlying, contributing or direct cause in 6060 deaths. MS associated mortality remained stable with a slight preponderance among males until after 1980, and have since increased preferentially among females. Throughout the study period the mean annual increase was 1.25% for females and 0.3% for males (p < 0.0001). Age-period-cohort analysis revealed limited evidence of cohort effects for the gender differences; the best fitting model only included gender-age and gender-period interaction terms. The period effect evened out for males in the last three decades but increased for females, especially among the oldest age-groups. In conclusion, the increased female: male mortality ratio in MS associated mortality is driven mainly by increased mortality among females in the three last decades, particularly in the older age groups. It is best explained by disproportional period effects, providing evidence of time-varying external factors including improved access to diagnosis among females. [ABSTRACT FROM AUTHOR]

Objective: In Norway, diagnoses from specialist health care visits, drug prescriptions, and causes of deaths are registered in compulsory health registers. We aimed to determine amyotrophic lateral sclerosis (ALS) prevalence from 2009 to 2015 by combining these registers. Methods: We validated the Norwegian Patient Registry (NPR) through hospital files, and linked it with the Norwegian Cause of Death Registry and the Norwegian Prescription Database. Poisson regression models were fitted for estimating gender ratios, time trends and possible interactions. Similar models were used for mortality data subtracted from the dataset. Results: Eleven percent of patients with at least one ALS-related entry in NPR did not have ALS. ALS prevalence could nevertheless be reliably estimated through ascertaining cases identified in two separate registers, or with at least two entries in NPR with first entry within four years prior to prevalence date. ALS prevalence remained stable, and was 7.6/100,000 (95% CI 6.9-8.4) at 31st December 2015. Mean male:female ratio was higher for prevalence (1.8; 95% CI 1.6-2.0) than for mortality (1.5; 95% CI 1.2-1.8) (p = 0.04). There were also significant regional differences in prevalence (p < 0.01) but not in mortality. Conclusions: Norwegian compulsory health registers provide reliable tools for ALS surveillance, and suggest gender and regional differences in survival after diagnosis. [ABSTRACT FROM AUTHOR]