MS prevalence in New Zealand rose by one-third from 2006-2022: Study
Largest spikes seen for Māori and Pacific peoples, Asian ethnic groups
Among people in New Zealand, the proportion of individuals with multiple sclerosis (MS) — the disease’s prevalence, or how common it is — has grown by about one-third in recent decades, a new study found.
In 2006, 72.4 of every 100,000 people who lived in the country had MS, the data showed. As of 2022, this number had risen to 96.6 per 100,000.
The team noted that the increases in prevalence seen were particularly higher in Māori — the indigenous people of mainland New Zealand — and Pacific populations, as well as in Asian ethnic groups. However, the prevalence was lower in people living in more deprived areas, “possibly reflecting underdiagnosis due to difficulties accessing and navigating healthcare,” the researchers wrote.
According to Amanda Rose, national manager of Multiple Sclerosis New Zealand, limited access to healthcare is a serious problem in the island country.
“Too many New Zealanders face delays in being diagnosed with MS due to limited access to specialist neurologist appointments and MRI scans,” Rose said in a news story from the University of Aukland, where the research took place.
In addition to updating prevalence estimates, the research team developed a methodology to identify individuals with MS in certain populations using administrative health data.
The study, “Identifying multiple sclerosis in linked administrative health data in Aotearoa New Zealand,” was published in the New Zealand Medical Journal.
Researchers used health records, census data for updates
Understanding both the prevalence of MS and the characteristics of patients in a given country is essential to guide decision-making around resource allocation, healthcare planning, and the development of targeted support services, the researchers noted.
Because both prevalence rates and patient demographics can shift over time — often due to factors like improved diagnostics, aging populations, and changing environmental risks — ongoing data collection is crucial to ensure healthcare strategies remain effective and responsive.
In 2006, the New Zealand national MS prevalence study provided key information about how common the neurodegenerative disease was in the country, which is also known as Aotearoa, a name from the indigenous Māori language. It also helped researchers identify characteristics of people living with the condition.
Now, the research team set out to update that study with the help of administrative health records.
Using data from the Integrated Data Infrastructure (IDI), a linked database of anonymous administrative health records, census, and survey data, as well as records of hospitalizations, healthcare assessments, and pharmaceutical dispensing related to MS, the team determined the prevalence of MS in the total resident population and certain subgroups.
European New Zealanders are being diagnosed with MS at a higher rate. … We found MS increased substantially for Māori, Pacific peoples, and Asian ethnic groups over the same period.
While the prevalence of MS in New Zealand increased by about one-third from 2006 to 2022, certain subgroups saw their prevalence increase even further. For example, while rates among those with Māori descent continued to be lower than in white European residents, they more than doubled since the 2006 study, from 15.9 to 33.1 per 100,000, the data showed.
“While European New Zealanders are being diagnosed with MS at a higher rate (132.4 per 100,000), we found MS increased substantially for Māori, Pacific peoples, and Asian ethnic groups over the same period,” said Natalia Boven, PhD, a postdoctoral fellow at the University of Auckland and the first author of the study.
Underdiagnosis suspected in economically deprived regions
Populations of different regions also had differing rates of MS, with northern latitudes showing a lower prevalence than southern latitudes. Southland, the southernmost area of the country, had the highest rates, the data showed. These were nearly four times higher than in Aukland, a northern area with the lowest MS incidence.
“The latitudinal gradient may be related to greater vitamin D exposure in northern regions, which is thought to be potentially protective against MS, as well as differences in ethnic composition across Aotearoa,” the researchers wrote.
In regions with more economic deprivation, MS rates were also lower, which the researchers believe may indicate underdiagnosis due to healthcare barriers. Such barriers include difficulty in accessing healthcare resources and a shortage of resources, the team noted.
“The longstanding shortage of neurologists in Aotearoa has created long waiting lists for many people with neurological conditions, including MS,” Rose said. “We’ve been advocating for over [10] years to increase our number of neurologists, with little to no progress.”
While the IDI allowed the research team to look broadly at population-level trends, it carried some limitations, the study noted. Without confirmed diagnoses, the team noted they may have inadvertently excluded some people with MS and included some without MS. For example, some individuals initially misdiagnosed with MS may have been included in the final counts.
Multiple Sclerosis New Zealand, which helped fund this study, will now support follow-up research that will use the IDI to explore the demographic and socioeconomic characteristics of people living with MS in the country.
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