MS Risk, Latitude Link May Be Explained by Healthcare Spending
MS occurred significantly more frequently in high-income than low-income countries, study showed
How much a country spends on healthcare is associated with the prevalence of multiple sclerosis (MS), with higher spending nations seeing a greater number of MS cases, a study found.
MS cases might be underestimated in low-income nations that put less money into the healthcare system, resulting in reduced access to medical experts and equipment needed to make an MS diagnosis, the researchers suggested.
The findings also provide a possible explanation for the link between living at higher latitudes — farther from the equator — and a greater MS risk.
“Healthcare access significantly contributes to the global variations in MS prevalence, especially since national wealth rises with latitude and likely results in significant underestimation of MS prevalence in countries with lower health expenditure,” the researchers wrote.
The study, “Association of Multiple Sclerosis Prevalence With Sociodemographic, Health Systems, and Lifestyle Factors on a National and Regional Level,” was published in Neurology.
The reported prevalence of MS varies by country and geographical region, with a higher prevalence found among those living farther from the equator. That link has often been attributed to low vitamin D levels, as a result of reduced exposure to sunlight in higher latitudes, but that alone can’t fully explain the association.
Because countries farther from the equator are more likely to be wealthier than those nearer to the equator there is a possibility factors relating to national wealth, healthcare systems, and lifestyle might also play a role in the relationship between latitude and MS.
A research team at Johns Hopkins University examined scientific studies and databases to determine the current prevalence of MS in 203 countries and territories, and grouped them by geographic location and income levels.
The researchers then analyzed whether economic factors, healthcare systems, or lifestyle factors might drive differences in MS prevalence. Before the final analysis, data were adjusted for other factors that could influence MS risk, including age and sex.
Results showed a significant association between a higher latitude and a greater MS prevalence in the six evaluated geographic regions, whereas the availability of universal healthcare coverage was linked to higher prevalence everywhere but Southeast Asia.
When countries were grouped by income level, it was observed MS occurred significantly more frequently in high-income countries compared with low-income nations — the average MS prevalence was 46 per 100,000 people vs. 10 per 100,000 people, respectively.
In high income countries, a higher rate of MS was linked to multiple factors, including gross domestic product per capita — the economic output of a nation per person — health expenditures per capita, and the number of neurologists. Tobacco, obesity, and the number of available MRI machines were not linked to MS risk in those nations.
In contrast, none of these factors were associated with MS rates in low-income countries which could be due to the fact that these factors varied little among individual low-income countries.
In final statistical models, healthcare spending per capita and latitude were overall significantly associated with MS prevalence. Specifically, with each one standard deviation increase in latitude, MS prevalence increased by 0.65. Standard deviation is a measure of the dispersion, or variability, in a set of data.
High-income countries spent more on healthcare — $2,805 per person — compared with $45 per person in low-income areas. For each one standard deviation increase in healthcare spending per person a country’s MS prevalence increased by 0.49.
Data showed the money a country spent on healthcare could explain about 20% of the link between latitude and MS risk.
“Health expenditure per capita is strongly associated with national MS prevalence, suggesting theories that attribute variations in MS prevalence primarily to latitude effects on vitamin D are incomplete,” the researchers wrote.
Differences in data sources used could have influenced the accuracy of some estimates in the study.
According to a news release, Deanna Saylor, MD, a neuroimmunologist at Johns Hopkins and the study’s lead author, said the findings suggest greater investments in healthcare among higher-income nations leads to higher reporting rates of MS.
Saylor said strategies are needed to prevent the shortages in healthcare professionals and equipment that hinder MS diagnoses in low-income countries.
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