Glynnis Clarke

MS prevalence in New Zealand, an ethnically and latitudinally diverse country

Background: The prevalence of multiple sclerosis (MS) is not uniform, with a latitudinal gradient of prevalence present in most studies. Understanding the drivers of this gradient may allow a better understanding of the environmental factors involved in MS pathogenesis. Method: The New Zealand national MS prevalence study (NZMSPS) is a cross-sectional study of people with definite MS (DMS) (McDonald criteria 2005) resident in New Zealand on census night, 7 March 2006, utilizing multiple sources of notification. Capture—recapture analysis (CRA) was used to estimate missing cases. Results: Of 2917 people with DMS identified, the crude prevalence was 72.4 per 100,000 population, and 73.1 per 100,000 when age-standardized to the European population. CRA estimated that 96.7% of cases were identified. A latitudinal gradient was seen with MS prevalence increasing three-fold from the North (35°S) to the South (48°S). The gradient was non-uniform; females with relapsing—remitting/secondary-progressive (RRMS/SPMS) disease have a gradient 11 times greater than males with primary-progressive MS (p < 1 × 10-7). DMS was significantly less common among those of Māori ethnicity. Conclusions: This study confirms the presence of a robust latitudinal gradient of MS prevalence in New Zealand. This gradient is largely driven by European females with the RRMS/SPMS phenotype. These results indicate that the environmental factors that underlie the latitudinal gradient act differentially by gender, ethnicity and MS phenotype. A better understanding of these factors may allow more targeted MS therapies aimed at modifiable environmental triggers at the population level.

Assessing possible selection bias in a national voluntary MS longitudinal study in Australia

Background: Surveying volunteer members of a multiple sclerosis registry is a very cost-effective way of assessing the impact of the disease on life outcomes. However, whether the data from such a study can be generalised to the whole population of persons living with MS in a country or region is unclear. Methods: Here we compare the demographic and disease characteristics of participants in one such study, the Australian Multiple Sclerosis Longitudinal Study (AMSLS), with two well-characterised MS prevalence studies with near-complete ascertainment of MS in their study regions. Results: Although some differences were found, these largely represented the effects of geography (sex ratios) and local factors (national immunomodulatory therapy prescribing requirements), and the cohorts were otherwise comparable. Overall, despite comprising only 12–16% of MS cases in Australia, the AMSLS is highly representative of the MS population. Conclusions: Therefore with some minor caveats, the AMSLS data can be generalised to the whole Australasian MS population. Volunteer disease registries such as this can be highly representative and provide an excellent convenience sample when studying rare conditions such as MS.

16. Prevalence of multiple sclerosis in New Zealand

Multiple sclerosis (MS) is thought to result from a complex interplay of genetic and environmental factors. The degree to which genetic factors contribute and the existence of a latitudinal gradient in the prevalence of multiple sclerosis remain controversial. The studies that have shown geographical differences in prevalence have varied widely in terms of the size and ethnicity of the populations surveyed; the way in which MS was diagnosed: and in the completeness of case ascertainment. Knowledge of MS prevalence across a whole country therefore, could provide valuable information about the presence of a latitudinal gradient and about the genetic factors which contribute to the risk of developing MS. New Zealand is ideally suited to an observational study examining these factors as it has a geographically well defined population of manageable size (4,027,938) with a national healthcare system and geographical extent over 13 degrees of latitude (34-47 degrees south).

Multiple sclerosis in New Zealand Māori

The prevalence of MS in New Zealand in 2006 was 73.2 (age standardized per 100,000) while for those with indigenous Māori ancestry it was 3.6 times lower at 20.6. Earlier regional surveys (1968–2001) all reported much lower, or zero, prevalence for Māori than European. There was no evidence for differences in MS between those with and without Māori ancestry in either clinical features or latitude, confirming that Māori ancestry does not produce the reported increase in prevalence with latitude. It is likely that prevalence is increasing in low risk Māori; however, MS prognosis is independent of Māori ancestry.

Multiple Sclerosis impact on employment and income in New Zealand

We investigated the demographic, social and clinical characteristics associated with employment status and income for people with multiple sclerosis (MS) in New Zealand (NZ).

An investigation of the relationship between latitude and multiple sclerosis severity in New Zealand

Associations between latitude and the prevalence of multiple sclerosis are well recognized,1–3 although the association is not seen in some geographical regions.4 The 2006 New Zealand National Multiple Sclerosis Prevalence Study (NZMSPS)5 reported a three-fold increase in multiple sclerosis prevalence with increasing latitude from northern (37.9°S) to southern (45.8°S) regions of New Zealand. In addition, the study found that of the 2422 subjects assessed, 60% had moderate to severe disability (Expanded Disability Status Score (EDSS)6 score 3.5 to 9.5). There has been little previous investigation of whether disease severity is related to latitude. We therefore investigated, using data acquired in the NZMSPS, whether latitude is associated with disease severity in New Zealand.

Disability profile of multiple sclerosis in New Zealand.

New Zealand is a high risk region for multiple sclerosis (MS). The aim of this study was to investigate demographic, clinical and temporal factors associated with disability status in the New Zealand National Multiple Sclerosis Prevalence Study (NZNMSPS) cohort. Data were obtained from the 2006 NZNMSPS with MS diagnosis based on the 2005 McDonald criteria. Disability was assessed using the Expanded Disability Status Scale (EDSS). Disability profiles were generated using multiple linear regression analysis. A total of 2917 persons with MS was identified, of whom disability data were available for 2422 (75% females). The overall disability was EDSS 4.4±standard deviation 2.6. Higher disability was associated with older age, longer disease duration, older and younger ages of onset, spinal cord syndromes with motor involvement at onset, and a progressive onset type. Lower disability was associated with sensory symptoms at onset and a relapsing onset type. Overall, the factors studied explained about one-third of the variation in disability, and of this, about two-thirds was accounted for by age, age of onset and disease duration and one-third by the nature of first symptoms and type of disease onset (progressive or relapsing). Current age, age at onset and disease duration all had independent associations with disability and their effects also interacted in contributing to higher disability levels over the course of the disease.