Background/Purpose: Economic analyses of SLE often include only direct healthcare costs.  Indirect costs, particularly those attributable to lost productivity in unpaid labour, are often overlooked, which is especially relevant for a disease disproportionately affecting women.  We assessed indirect costs due to lost productivity in both paid and unpaid labour, stratified by gender, in a national multi-centre SLE cohort.

Methods: Patients fulfilling the ACR or Systemic Lupus International Collaborating Clinics (SLICC) SLE Classification Criteria from 6 centres completed a validated questionnaire on lost productivity.  Total indirect costs included: 1) absenteeism (time lost from paid labour because of illness), 2) presenteeism (degree of productivity impairment in paid/unpaid labour, based on a visual analogue scale), 3) opportunity costs (additional time patients would be working in paid/unpaid labour if not ill).  Opportunity costs were calculated as the difference between the time patients reported working versus that worked by an age, sex, and geographic-matched general population in paid and unpaid labour.  Indirect costs from paid and unpaid labour were valued using age-and-sex-specific wages from Statistics Canada.  The association of gender with each of the components of annual indirect costs was assessed (adjusted for race/ethnicity, age, disease duration, and the SLICC/ACR Damage Index [SDI]) using random effects linear regression modelling, which allows for correlations for multiple observations per patient.  Costs are expressed in 2023 Canadian dollars.

Results: 1804 patients participated, 90.8% female, 66.9% white, mean age at diagnosis 33.7 (SD 13.9) years, mean SLE duration 14.7 (11.7) years, and mean SDI 1.3 (range 0-12.0). Patients were followed a mean of 4.9 (range 1.0-9.6) years with 48.9% employed (49.5% among females, 44.0% among males) at the initial and 37.0% (37.1% among females, 36.7% among males) at the final observation (Table 1).  Overall, total annual indirect costs were $36 405 (absenteeism: $829; presenteeism in paid labour: $4624; presenteeism in unpaid labour: $8922; opportunity costs in paid labour: $8512; opportunity costs in unpaid labour: $13 519).  Among women, opportunity costs from unpaid labour were 38.8% ($14 175/$36 538) and from paid labour 21.3% ($7802/$36 538) of total indirect costs; among men, opportunity costs from unpaid labour were 19.6% ($6878/$35 064) and from paid labour 44.7% ($15 685/$35 064) of total indirect costs (Figure 1).  Regression modelling showed that while women incurred higher opportunity costs from unpaid labour (coefficient $7309, 95%CI $3514, $11 105), they incurred lower opportunity costs from paid labour (coefficient -$8336, 95%CI -$12 524, -$4147) (Table 2).

Conclusion: Indirect costs in SLE, particularly resulting from unpaid labour, are substantial, especially in women, where they represent 38.8% of total indirect costs versus 19.6% in men.  Hence, economic analyses weighing costs and benefits of novel/emerging therapies should incorporate costs resulting from lost productivity, including those in unpaid labour, which are of particular importance in diseases disproportionately affecting women.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-forgotten-costs-of-sle-estimating-indirect-costs-in-a-national-sle-cohort/