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Multiple sclerosis in the Orkney and Shetland Islands. I: Epidemiology, clinical factors, and methodology
Abstract:
An epidemiological and clinical study of multiple sclerosis (MS) in the Orkney and Shetland Islands showed that the prevalence rate of the disease is the highest in the world (309 and 184/100 000, respectively). The clinical entity, MS, is similar to that found in other parts of the world, except that optic neuritis not followed by MS is rare. Analysis of death certificates indicated that MS has probably occurred at the same rate in these islands for nearly a century. Although the incidence of MS is high, the incidence rate has remained constant over time. A rapidly increasing prevalence of MS has occurred in Orkney, with a more modest increase in Shetland, over the past 20 years, which is largely due to an increase in survival. Demographic factors, case ascertainment, and emigration have contributed little to the increasing prevalence of MS in these islands.
Insights
Multiple sclerosis (MS) prevalence is highest globally in Orkney and Shetland. While incidence remains stable, increased survival has driven rising prevalence over two decades.
Area of Science:
- Epidemiology
- Neurology
- Public Health
Background:
- Multiple sclerosis (MS) is a chronic neurological disease affecting the central nervous system.
- Geographic variations in MS prevalence suggest environmental or genetic influences.
- Previous studies indicated higher MS rates in certain island populations.
Purpose of the Study:
- To determine the prevalence and incidence of multiple sclerosis (MS) in the Orkney and Shetland Islands.
- To analyze clinical characteristics of MS in these island populations.
- To investigate trends in MS prevalence and incidence over time and identify contributing factors.
Main Methods:
- Epidemiological and clinical study design.
- Prevalence and incidence rate calculations (per 100,000 population).
- Analysis of death certificates and demographic data.
- Review of clinical features, including optic neuritis.
Main Results:
- Highest global multiple sclerosis (MS) prevalence recorded: 309/100,000 in Orkney and 184/100,000 in Shetland.
- MS clinical presentation similar to other regions, with rare optic neuritis without subsequent MS.
- Stable MS incidence over time, but rapidly increasing prevalence in Orkney and modestly in Shetland over 20 years due to increased survival.
Conclusions:
- The Orkney and Shetland Islands exhibit the world's highest multiple sclerosis (MS) prevalence.
- Increased patient survival, not changes in incidence, explains the rising MS prevalence in recent decades.
- Demographic factors, case ascertainment, and emigration played minimal roles in the observed prevalence increase.