BACKGROUND
Systemic sclerosis (SSc) is an autoimmune disease with female preponderance. Although higher prevalence of SSc in women than in men is well-known, no studies have appropriately analyzed the risk of incident SSc according to sex, adjusting for potential confounders. Therefore, the risk association between female sex and incident SSc remains unclear.
OBJECTIVE
This study aims to assess the association between female sex and risk of incident SSc, and to identify subsets of individuals in whom the risk difference according to sex is more prominent.
METHODS
An analysis of a Korean nationwide cohort of 9,894,996 individuals was conducted. All individuals were followed up from 2009 to 2019. Cox proportional hazard models were used to assess the risk of incident SSc in women, using men as the reference. Subgroup analysis was conducted by stratifying individuals according to multiple covariates.
RESULTS
Female sex was significantly associated with a higher risk of incident SSc (adjusted hazard ratio [aHR], 5.275; 95% confidence interval, 4.346–6.403). The effect size of female sex was more pronounced in middle-aged individuals (aHR, 5.020 [<40 years] vs. 5.868 [40–64 years] vs. 2.734 [≥65 years]; p-interaction < .001); those without abdominal obesity (aHR, 5.863 vs. 3.658; p-interaction = .005); those who did not exercise regularly (aHR, 5.701 vs. 3.932; p-interaction = .030); and those without hypertension (aHR, 5.996 vs. 4.053; p-interaction = .010) or dyslipidemia (aHR, 5.857 vs. 3.330; p-interaction = .001).
CONCLUSIONS
Female sex was associated with a higher risk of incident SSc. The association was more prominent in middle-aged individuals, those without abdominal obesity, those who do not exercise regularly, and do not have hypertension or dyslipidemia. Closer surveillance for SSc could be helpful in these subsets of women.