In New Zealand, only two studies had been undertaken before 2017 to measure the incidence of multiple sclerosis (MS), both are regional, and were conducted between two and four decades ago – thus the true incidence of MS in the country was unknown. In addition, no previous study reported incidence or the rate of conversion from a first demyelinating event (FDE) to MS in a national population, which has lead to a significant knowledge gap of the natural history of early MS.
The specific aims of the study were:
Knowledge about environmental and lifestyle factors and of the natural history of demyelinating syndromes is essential in order to develop early intervention strategies. The results of this study would help guide doctors in making treatment decisions and provide patients with a clearer idea of their risks of further demyelinating events.
The results have also supported MSNZs advocacy work in pushing for funding for new treatments for the management of MS.
The New Zealand Multiple Sclerosis incidence study began recruitment in 2012. The aim of the study was to identify all persons throughout NZ who were either diagnosed with MS or experienced their first symptoms of demyelination between June 1st 2012 and May 31st 2014.
Number of recruits
The results confirm that NZ continues to be a high risk country for MS with around 134 people diagnosed across the country each year.
The age-standardised incidence (ASI) was 3.3 (95% CI 2.9 – 3.7) per 100,000 population for the entire country. For males the incidence was 1.6 (95% CI 1.2- 2.0) / 100,000 and for females 4.8 (95% CI 4.2 – 5.5) /100,000
Male to female ratio of 1:3.
The average age at which people developed their first symptoms was 37.8 +11.8 years. This is older than the average age recorded in previous studies.
The mean age at diagnosis was 42.2 years indicating that there is a significant delay between the onset of first symptoms and diagnosis.
The mean EDSS at diagnosis was 2.3 ± 1.6.
A further objective of the study was to calculate the number of new cases (incidence) of MS by region in order to investigate the relationship between the incidence of the disease and latitude. Residential data obtained at the time of diagnosis showed a 3.8 fold increase in ASI between the northern (36.70S) and southern (45.80S) region of the country. As shown in Figure 1, MS incidence for the total population increased by 0.68 ± 0.12 per 100,000 population per degree of latitude (p<0.01).
The Multiple Sclerosis (MS) Research group was formed in 2005 by a collaboration of neurologists and researchers working at Christchurch Hospital and the Universities of Otago and Canterbury.