ILD seen to increase risk of death for scleroderma patients in study
More risk found for those with interstitial lung disease than SSC alone
Systemic sclerosis (SSc) patients with interstitial lung disease (ILD) have a higher risk of death when compared with individuals with SSc alone, according to a new population-based study conducted in Denmark.
The presence of additional co-occurring disorders, or comorbidities, other than ILDs, was found to gradually increase the risk of death for SSc patients in the study.
“The high prevalence of comorbidities in SSc had extensive impact on mortality,” the researchers wrote, noting that, overall, “mortality was increased in males, in young adults and in SSc-ILD, underlining the excess mortality associated with ILD.”
According to the team, “these findings emphasise the importance of timely diagnosis and optimal management of organ involvement and comorbidities in SSc.”
The study, “Comorbidity and mortality in systemic sclerosis and matched controls: Impact of interstitial lung disease. A population based cohort study based on health registry data,” was published in the journal Chronic Respiratory Disease.
Investigating the risk of death in SSc patients with and without other disorders
Also known as scleroderma, SSc is characterized by the formation of scar tissue (fibrosis) in the skin. This often expands to internal organs, such as the lungs, kidneys, and heart, and those of the digestive tract.
ILDs, a group of diseases characterized by lung inflammation and fibrosis, are found in up to 50% of SSc patients and are associated with an increased risk of death.
Now, a team led by researchers at the University of Southern Denmark conducted a population-based study in that country to learn more. The aim was to assess the impact of co-occurring diseases on mortality in a group of people with SSc as compared with matched individuals from the general population without the disease, who served as controls.
The researchers separately also evaluated the outcomes of SSc patients with interstitial lung disease — commonly referred to as SSc-ILD — or without ILD, here identified as non-ILD SSc.
Patients with a first SSc diagnosis between 2002 and 2015 were included in the analysis. The Deyo-Charlson comorbidity score was used to assess the burden of comorbidities.
Data were analyzed from 1,732 SSc patients, including 258 (14.9%) with SSc-ILD, and 6,919 matched controls from the Danish National Patient Registry (DNPR). The team specifically assessed the burden of comorbidities within three years before and after the scleroderma diagnosis.
In the three years before SSc diagnosis, the majority of patients in the non-ILD SSc (62.8%) and SSc-ILD groups (60.5%) were free of co-occurring conditions, as shown by a score of zero in the Deyo-Charlson comorbidity score. Among the controls, the percentage of individuals with no comorbidities was always greater than 80%.
Within three years of a scleroderma diagnosis, the proportion of patients without comorbidities dropped to 9% in the non-ILD SSc group and to 3.9% in the SSc-ILD group.
At that time, the percentage of non-ILD SSc patients with a higher comorbidity burden — a Deyo-Charlson comorbidity score higher than three — increased from 8.9% to 24.3%. A similar trend also was seen in the SSc-ILD group, where the proportion of patients with a higher comorbidity burden increased from 7.4% before diagnosis to 25.6% after the scleroderma diagnosis.
Higher risk of death seen for men, young adults
The most common comorbidities seen in SSc patients were musculoskeletal disorders — diseases affecting bones, muscles, tendons, and ligaments — and those affecting connective tissues, which help support other tissues and organs in the body. These were followed by cardiovascular diseases in the non-ILD SSc group and by respiratory diseases in the SSc-ILD group.
Overall, SSc patients had a higher risk of death compared with controls. Specifically, this comparison showed the risk of death was higher by 2.6 times in patients in the non-ILD SSc group and by 4.2 times in the SSc-ILD group.
Among scleroderma patients, young adults, defined as those ages 18-40, were found to be at a particularly high risk of death — higher by 6.9 times compared with controls. The risk of mortality was higher by 7.7 times compared with controls among those aged 41-50. Men with SSc also had a mortality risk that was higher by 3.1 times.
In the non-ILD SSc group, researchers observed that the risk of death increased gradually with comorbidity burden. Cancer was the most frequent cause of death in SSc patients, with 24.9% of the deaths, followed by musculoskeletal and connective tissue diseases, at 22.7%.
“Our study showed that the burden of comorbidities in SSc had an extensive impact on mortality,” the researchers wrote.
A key limitation to this study, according to the team, was a lack of some clinical information, such as the type of scleroderma, that could not be obtained from the registry.
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