Epidemiology of Spinal Muscular Atrophy in Iceland: A Population-Based Study

Spinal muscular atrophy (SMA) is a hereditary neuromuscular disorder characterized by the progressive degeneration of motor neurons and the subsequent loss of muscle function. With new therapeutic options for SMA, it is important to understand the epidemiology of the disease. As of January 2024, SMA has been included in newborn screening in Iceland.

The aim of the study was to estimate the point prevalence and incidence rate of SMA in Iceland.

This retrospective, population-based study collected data from the institutional records of the University Hospital of Iceland, pediatricians and privately practising neurologists. The incidence period was from 1997 to 2024, and the point-prevalence day was January 1st 2025. The incidence was calculated per 100,000 live births and the point prevalence per 100,000 residents.

On the prevalence day, 23 individuals had SMA in Iceland, resulting in a point prevalence of 5.9/100,000. The prevalence of SMA in children under 18 years was 10.6/100,000. During the incidence period, 17 cases of SMA were born, yielding an incidence rate of 13.9/100,000 live births. Of those born during the incidence period, twelve were alive on the prevalence day, resulting in a fatality rate of 29.4%. Two cases of SMA have been diagnosed through newborn screening since it began.

The incidence and point prevalence of SMA in Iceland are high compared to those reported in other countries.