Sex Differences in Lupus Mortality

A comprehensive US population-based study identified an average 22-year and 12-year deficit in life expectancy among females and males with systemic lupus erythematosus (SLE), respectively, compared with the general population.

Background
In the United States, SLE is a source of significantly decreased life expectancy. While marked differences have been observed between the sexes in terms of the incidence, prevalence, and clinical manifestations of SLE, this area is still poorly understood.

Falasinnu and colleagues¹ at Stanford School of Medicine identified sex-based differences in the causes of death among SLE decedents in the United States and recognized clinically relevant comorbidities that may warrant careful consideration in patients’ clinical management.

The studyThis study examined SLE-related deaths using the 2014 National Center for Health Statistics multiple cause of death (MCOD) database, a population-based electronic medical recording of all death certificates issued in the United States. The analysis considered not only the number of death certificates listing SLE as the underlying cause of death, but also those listing SLE in general.

Demographic information considered included age, race/ethnicity, sex, educational attainment, foreign-born status, marital status, and pregnancy status. SLE decedents were compared with non-SLE decedents in the general population belonging to the same age group.

The findings
In 2014, there were 2,660,497 deaths in the United States, of which 2036 (0.1%) listed SLE among the causes of death. Approximately 86.2% of SLE deaths occurred among females, with a median age at death of 59 years and the highest proportion of deaths occurring between 45 and 64 years of age. In comparison, the overall median age at death for females in the general population was 81 years, and the majority of deaths occurred among females over 65 years of age.

Black females experienced the greatest burden of SLE mortality. Approximately 32% of all female SLE decedents were black, compared with only 11% of non–SLE-related deaths in the general population. Female decedents with SLE had a slightly higher proportion of foreign-born individuals than the general population, but there were no other significant demographic differences. The most frequently listed comorbidities among female decedents with SLE were septicemia (4.32%) and hypertension (3.04%).

Among male decedents with SLE, the median age at death was 61 years, compared with 73 years in the general population. Of male decedents with SLE, 23.5% were black, compared with only 12% in the general population. The age-standardized mortality was highest among American Indian males. There were no other demographic differences related to SLE among male decedents. The most frequently listed comorbidities among male decedents with SLE were heart disease (3.70%) and diabetes mellitus with complications (3.61%).

Implications for physicians and future research
This study offers an opportunity to better describe the association between SLE and related comorbidities in the context of mortality, although the MCOD data have a number of limitations. Inaccuracy on death certificates can lead to the underestimation of the SLE mortality burden, and researchers were unable to differentiate between causes of death that were related to the natural age process, disease activity, and drug therapy. Still, the MCOD data provide a comprehensive understanding of the population-based burden of SLE mortality.

While female SLE patients tend to have more frequent disease exacerbations, male patients appear to have significantly greater multisystemic damage accrual and disease severity. Greater disease severity among male SLE patients may be related to under diagnosis due to selective attention given to females by physicians during clinical decision-making. This potential for gender bias needs to be carefully considered.

Racial minorities generally have a disproportionately higher burden of mortality. The scope and degree of these differences in SLE are particularly pronounced, with mortality rates among black females nearly four times as high as those in white females. “Our findings reinforce the urgent need for interventions that reduce morbidity and mortality in patients with SLE to improve health outcomes and ultimately reduce health disparities,” the researchers write. They note that novel translational research programs are currently underway to attempt to address these disparities.

Clinically relevant comorbidities also need to be considered more carefully in the course of patients’ clinical management and the natural history of SLE. This study revealed future targets for the investigation of sex-based differences and directions for epidemiological research. “A comprehensive understanding of causes of death and the related comorbidities can improve clinical diagnostic and therapeutic strategies, impact survival outcomes in patients living with SLE, and enhance population-based disease surveillance estimates,” the researchers conclude.

References:

1. Falasinnu T, Chaichian Y, Simard JF. Impact of sex on systemic lupus erythematosus-related causes of premature mortality in the United States. J Womens Health (Larchmt). 2017;26:1214-1221. doi: 10.1089/jwh.2017.6334.