Comorbidity in Multiple Sclerosis
Multiple sclerosis (MS) is a chronic autoimmune disorder affecting the central nervous system, characterized by a wide range of symptoms and complications. Despite advancements in understanding and managing MS, survival rates for individuals with MS remain lower compared to the general population. The 2015 study by Marrie et al., titled Effect of Comorbidity on Mortality in Multiple Sclerosis, delves into how comorbidities affect mortality in the MS population. The study not only compares survival rates between those with MS and a matched general population cohort but also examines how various comorbid conditions influence mortality in both groups.
Study Design and Methodology
The study utilized a population-based approach, relying on administrative data from Manitoba, Canada. The dataset included 5,797 individuals diagnosed with MS and 28,807 matched controls from the general population. The controls were matched by sex, year of birth, and region of residence. The authors employed Cox proportional hazards models to evaluate the risk of death associated with comorbidities, adjusting for factors such as sex, socioeconomic status, and region of residence. Importantly, the study stratified analyses by birth cohort to account for generational shifts in disease outcomes.
Key Findings: Reduced Survival in MS
One of the key findings was the median survival from birth in the MS population, which was 75.9 years, compared to 83.4 years in the matched population. This result underscores that individuals with MS face a significantly higher risk of death, with an adjusted hazard ratio (HR) of 2.40, indicating a more than twofold increase in mortality risk. The study confirms earlier reports that survival for individuals with MS has improved over time but remains consistently lower than expected when compared to the general population.
The Role of Comorbidities in MS Mortality
Comorbidities, such as diabetes, ischemic heart disease (IHD), chronic lung disease, and psychiatric conditions like depression and anxiety, were strongly associated with increased mortality in both the MS and general populations. However, the magnitude of this association was generally lower in the MS population compared to the general population. For example, chronic lung disease and diabetes were linked to a lower relative hazard of death in the MS cohort than in the control cohort.
In contrast, depression emerged as a significant risk factor, with individuals suffering from both MS and depression having a higher mortality risk. Interestingly, anxiety was associated with a reduced hazard of death, suggesting that individuals with anxiety may engage in more health-seeking behaviors, which could mitigate the risk.
Causes of Death in MS
The study also examined the primary causes of death in the MS population. The most common causes were diseases of the nervous system (primarily MS itself), followed by circulatory system diseases, respiratory diseases, and infectious diseases. Mortality due to infectious and respiratory diseases was notably higher in the MS population, aligning with previous studies that point to the vulnerability of individuals with MS to infections and complications like pneumonia.
Interestingly, cancer mortality rates were lower in the MS population, a finding that has been reported in other studies as well, although the underlying reasons remain unclear. Some hypotheses suggest that the frequent healthcare visits by MS patients may lead to early detection and treatment of cancers, or there may be a biological factor at play related to MS or its treatments.
Implications and Recommendations
This study provides crucial insights into the role of comorbidities in MS mortality. While comorbid conditions do increase the risk of death in individuals with MS, the effect is not more pronounced than in the general population. This suggests that optimizing the management of comorbidities could be a key strategy in improving survival rates for MS patients.
The findings also emphasize the need for comprehensive healthcare strategies that address both MS and its associated comorbidities. Given the higher mortality rates from respiratory and infectious diseases, regular monitoring and proactive management of these conditions are essential for improving the quality of life and longevity in the MS population.
Conclusion
The study by Marrie et al. significantly advances our understanding of how comorbidities affect mortality in MS. While survival in the MS population has improved over time, it remains lower than in the general population. Comorbidities such as diabetes, IHD, and depression are important factors influencing mortality, but they do not disproportionately affect those with MS compared to the general population. As healthcare providers strive to improve outcomes for individuals with MS, a focus on the management of comorbidities alongside MS may hold the key to further extending survival and enhancing overall well-being.
References:
Marrie, R. A., Elliott, L., Marriott, J., Cossoy, M., Blanchard, J., Leung, S., & Yu, N. (2015). Effect of comorbidity on mortality in multiple sclerosis. Neurology, 85(3), 240-247.
