WP24/02: Access to disease-modifying treatments for multiple sclerosis by ethnicity and socioeconomic position

Working Paper 24/02

Natalia Boven
Julie Winter-Smith
Lisa Underwood
Vanessa Selak
Andrew Sporle
Deborah Mason
Anna Ranta
Alan Barber
Barry Milne

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system that causes a range of neurological symptoms, profound fatigue, physical disability, and cognitive impairment. Disease-modifying treatments (DMTs) are available to reduce disease progression, although rates of prescriptions are relatively low in Aotearoa, and it is not known whether these medications are being prescribed equitably. This study will examine whether there are differences in access to DMTs across ethnic groups and levels of socioeconomic position.

In particular, this study will test whether there are inequities across groups in receipt of any DMTs, and DMTs of varying efficacy.

The specific research questions are:

1. Of those with a record of MS prior to November 2014, did the odds of being dispensed a low efficacy DMT or no DMT differ by ethnicity and/or SEP during the period 2006-November 2014?
2. Of those with a record of MS prior to November 2014, did the odds of being dispensed a high efficacy DMT, moderate efficacy DMT, low efficacy DMT, or no DMT between November 2014 and March 2021 differ by ethnicity and/or SEP?
3. Of those with record of MS at any point prior to March 2021, did the odds of being dispensed a high-efficacy DMT between November 2014 and March 2021 differ by ethnicity and/or SEP?
4. Of those with a record of MS at any point prior to March 2018, did the odds of being prescribed frequent corticosteroids [indicating poorly controlled disease] differ by ethnic group and/or SEP for the period March 2018 – March 2021.
5. If there is a difference in the odds of being prescribed frequent corticosteroids by ethnic group and/or SEP between March 2018 and March 2021, was this mediated [explained] by the type of DMT used at the beginning of this period (high efficacy DMT, moderate efficacy DMT, low efficacy DMT, or no DMT).

Analyses will consist of a series of binary and multinomial logistic regression models. If group sizes are sufficient, differences will be examined for the Māori, Pacific, Asian and European ethnic groups, and across levels of education, occupation, income, and area deprivation. Given known associations between ethnicity and socioeconomic position, and within different aspects of socioeconomic positions, models will examine these predictors separately. Unadjusted and adjusted models will be examined. Adjusted models will control for age, gender, disability, year of first record of MS, and relevant comorbidities. Geographic patterns in dispensing of DMTs will also be examined.

These analyses will use data sources from the Integrated Data Infrastructure (IDI):

• Pharmaceutical dispensings
• Publicly and privately funded hospitalisations
• National Non-Admitted Patient Collection
• National Needs Assessment and Service Coordination Information (SOCRATES)
• interRAI
• Census 2013
• Census 2018
• Benefit dynamics
• Ministry of Education
• Tax records
• Address notification
• Personal details
• Estimated Resident Population

While this paper will focus on treatment inequities in MS, a wider aim of this project is to determine the suitability of using the IDI to identify complex chronic illnesses. To facilitate this, the characteristics of cohorts of people with MS identified in this study will be compared to other NZ-based studies.