British military personnel are at significantly higher risk of dying from multiple sclerosis than people in other occupations, a study reports.
The findings, in an article titled “Mortality from multiple sclerosis in British military personnel,” were reported in the journal Occupational Medicine. The results conflicted with an earlier study that included non-military controls.
University of Southampton researchers had done a previous study of mortality rates by occupation by checking records of residents of England and Wales. They noticed that the death rate among MS patients in the armed forces was much higher than that of people in other professions over three successive decades.
MS has a genetic component but is also influenced by environmental factors, including vitamin D deficiency, smoking and certain viruses. Researchers wanted to learn why so many military people die of MS, and the causes.
The team looked at the death records of men aged 20-74 between 1979 and 2010. They compared military people’s MS-related mortality rates and death rates from all motor neuron diseases with those of other occupations. They also compared rates across social classes, which in the military presumably means lower-ranking enlisted people, higher-ranking enlisted people, and officers.
They discovered that the MS-related mortality rate among military people was significantly higher than in other professions. The death rate from MS was also significantly higher than the rate from all motor neuron diseases in the armed forces.
Interestingly, military people did not have a higher MS-related death rate when the team divided those in the study into three social classes or when they compared the armed forces mortality rate to those of similar occupations, such as police and fire services.
The consistency of the findings, together with the high statistical significance observed, indicated that the results were not due to simple chance or a problem with the study method, the team said.
They speculated that the higher military death rate could stem from the close proximity in which military personnel live and work, which could facilitate the transmission of infections that have the potential to cause MS.
“When viewed together, our findings suggest that the persistently high proportion of deaths from MS in British military personnel is unlikely to be explained by chance, bias or confounding,” the team wrote. “The alternative possibility that there is an underlying occupational hazard is plausible. For example, the close proximity in which military recruits live and work might facilitate the transmission of one or more infections” that lead to MS.
The results conflicted with those of a study that analyzed hospital admissions due to MS in a population of former military personnel. It reported no increased incidence of MS-related admissions in former military people, compared with non-military controls.
Since such cohort studies are less prone to bias, the Southampton team called for more research on the topic.