Background/Purpose: Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that is associated with a high morbidity and mortality. The specific causes of death vary among ethnic groups or geographical locations.  The purpose of this study was to determine the mortality profile related to SLE in Puerto Rico using multiple-cause-of-death analysis.

Methods: Public use, multiple-cause-of-death mortality files from the National Center of Health Statistics were used to select death records of residents in Puerto Rico listing SLE (International Classification of Diseases, 10th Revision, codes M32.1 or M32.9) as an underlying cause of death (UCD) or as a non-underlying cause of death (NUCD) for years  2003-2013 .  Demographic data, gender-specific age-adjusted mortality rates, and associated causes of death were analyzed. Causes of death were classified into four groups:  SLE-related complications, infectious diseases, cardiovascular diseases, diabetes mellitus, and malignancy.  Proportionate mortalities were used to investigate associations between causes of death, calculating the ratio of observed to expected deaths (O:E ratio) for selected comorbidities. Mann-Whitney, chi-square and Fisher’s exact tests were used to evaluate statistical associations.

Results: In total, 393 SLE-related deaths were identified. Median age was 52 years (53 for females and 45 for males; p=0.216). Three hundred and forty five (87.8%) deaths occurred in women, for a female to male ratio of 7.2.   The age-adjusted mortality rate for SLE-related deaths for women was 166.5 deaths/million and 27.8 deaths/million for men (relative risk = 6.0; p < 0.001). In 308 deaths (78.37%), SLE was listed as the UCD.  Those listed with SLE as the UCD were younger (median age 51 vs. 57 years, p =0.008) and were more likely to die at a medical center (82.2% vs. 68.2%, p= 0.007) compared to those listed with SLE as a NUCD. In multiple-cause of death analysis, the most common causes of SLE-related deaths (UCD and NUCD) were infectious diseases (42.5%), SLE-related complications (37.4%), cardiovascular diseases (27.9%), diabetes mellitus (12.2 %), and malignancy (5.6%).  For men, SLE related complications (54.2% vs. 35.1%, p=0.016) and cardiovascular diseases (41.7% vs. 26.1%, p=0.038) were more common than in women. No significant differences were observed for infectious diseases, diabetes mellitus, and malignancy between men and women.  Among infectious diseases, bacterial infections were reported in 130 death certificates and sepsis in 124. The overall O:E ratio was >1 for bacterial infections (1.86, p < 0.001) and renal failure (1.45, p = 0.002).  The O:E ratio for malignant hypertensive disease , ischemic heart, cerebrovascular diseases and malignant neoplasms was < 1. 

Conclusion: In Puerto Rico, SLE deaths were more commonly associated with infectious disorders, particularly bacterial infections and sepsis.  Adhering to prevention and control measures of infection could be crucial in improving SLE survival in this population.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/mortality-of-systemic-lupus-erythematosus-in-puerto-rico-assessed-by-multiple-cause-of-death-analysis/