Background/Purpose: Low socioeconomic status (SES) is associated
with an increased risk of death as well as knee and/or hip osteoarthritis (OA).
SES and mortality has rarely been examined in individuals with OA. We therefore
sought to explore whether SES at baseline was associated with death before
follow-up assessments among those with knee and/or hip OA.

Methods:   The association between SES and all-cause
death over 25 years was explored in the Johnston County Osteoarthritis Project.
We used baseline data from 1,333 individuals aged ≥45 who entered the
cohort between 1990-1997 and who had known vital status at all three follow-up
periods. Participants had radiographically confirmed knee and/or hip OA at baseline
clinical assessment, defined as a Kellgren-Lawrence grade ≥2. Vital
status was assessed at 3 follow up points (F1: 1999-2004; F2: 2006-2010, F3:
2013-2015), and deaths were identified through participant provided contacts
and obituaries. SES measures at baseline included indicators for high school
(HS) education (<HS diploma vs.
≥HS diploma), block group poverty (BGP) (≥20% vs. <20%), homeownership (own their home vs. not), and annual household income (<$30K vs. ≥$30K). Multilevel logistic
regression models controlling for the primary sampling unit were used to estimate
odds ratios (OR) and 95% confidence intervals (CI) for the association between
individual SES measures at baseline and whether a death occurred separately for
each follow-up point. All models were adjusted for baseline age, race, sex,
cohort, education, BMI, use of an assistive walking device, history of smoking,
stroke, diabetes, heart disease, high blood pressure and depression, plus additional
adjustment for other SES measures.

Results: Mean age at baseline was 65.4 years, with 61.8% women and
one-third African American. There were 49.0% with <HS education, 43.9% lived
in areas with ≥20% BGP, 28.7% did not own their home and 82.6% had a
household income <$30K. There were 234 deaths which had occurred before the F1
assessment (18.1%), 528 deaths before F2 (41.1%) and 680 deaths before F3
(52.9%). Those with <HS education had an increased odds of death that
appeared to gain strength at subsequent follow up points (Table 1). By F3,
those with <HS education had a 50% increased odds of death (OR=1.52; 95%
CI=1.06-2.17). Although failing to reach statistical
significance, we observed a similarly elevated OR for BGP ≥20% at each
subsequent timepoint.

Conclusion: Among individuals with knee and/or hip OA, low
education is associated with death, where odds of death seems to increase at
subsequent follow-up periods. Results were independent of comorbidities and
sociodemographic measures commonly linked to increased mortality, although lack
of time-to-death and cause of death are limitations. Results suggest that those
with low education may need more intensive guidance regarding self-management from
clinicians.