Multiple Sclerosis in the Greenlandic population. A nationwide cohort study.

BACKGROUND

The Global Burden of Disease Group modelled a surprisingly high prevalence of Multiple Sclerosis (MS) in the Greenlandic population in 2016 of 290 per 100,000, higher than that in Denmark, a high-risk country of MS.

OBJECTIVE

Obtain accurate data on the burden (prevalence and incidence rates) of MS in Greenland, 1973 - 2014, overall and according to ethnicity.

METHODS

Greenlandic prevalence and incidence rates were estimated using validated data from the Danish Multiple Sclerosis Registry (Greenlandic citizens suspected of MS were until 2014 supposed to be transferred to Denmark). The relative risk of MS in the Greenlandic population versus that in the Danish was estimated as the ratio of observed to expected numbers of MS according to Danish national sex-, age- and period-specific MS incidence rates, i.e. Standardized Incidence Ratio (SIR).

RESULTS

In 2014, seven persons were living with MS in Greenland (prevalence=12.52 per 100,000) and 22 new MS cases were registered from 1973 to 2014 (incidence rate=0.97 (95 % CI; 0.64-1.47) per 100,000 person-years of risk). Inuit and Non-Inuit in Greenland, and Inuit in Denmark had MS risks of 2 % (SIR=0.02 (0.01-0.06)), 67 % (SIR=0.67 (0.42-1.04)) and 23 % (SIR=0.23 (0.13-0.39)) respectively, of that in the Danish Non-Inuit population. To enhance completeness, possibly at the risk of misclassification we included MS diagnoses from the Greenlandic and Danish National Patient registries. In 2014, prevalence of MS in Greenland was now 48.29 per 100,000.

CONCLUSION

Our study does not support prior claims of Greenland being a high MS risk country. MS is still relatively rare among Inuit living in Greenland.