Patient demographics, prior lower back injury, and the presence of hip osteoarthritis (OA) may have an effect on lumbar spine OA phenotype, according to a study published in Arthritis Care & Research.
Investigators examined data from the Johnston County OA Project, an ongoing longitudinal study of adults with OA living in a largely rural county in North Carolina. Residents >45 years of age were enrolled between 1991 and 1998 (original cohort; n=3187), and additional patients were enrolled between 2003 and 2004 (enrichment cohort). Participants attended follow-up visits approximately every 5 years, during which clinical and interview data were gathered. Lumbar spine radiograph data were added in 2003. In this analysis, investigators used multinomial regression models to determine the relationship between OA phenotype and demographic and clinical variables.
Data on age, sex, race, body mass index (BMI), low back pain and injury, and knee, hip, and hand OA were collected. Participants were categorized as having spine OA (SOA), facet joint OA (FOA), SOA and FOA, or neither SOA nor FOA.
The final analysis included data from 1793 participants, 63.8% of whom were women and 31.8% of whom were black. The mean age in this cohort was 66.2±10.1 years, and the average BMI was 30.7±6.2 kg/m2.
The prevalence of OA phenotypes were as follows: SOA only, 13.2%; FOA only, 22.8%; SOA and FOA, 46.0%; and neither SOA nor FOA, 18.0%. Black vs white participants were found to be less likely to have SOA plus FOA (odds ratio [OR], 0.51; 95% CI, 0.37-0.70) or FOA only (OR, 0.68; 95% CI, 0.49-0.95).
Women were more likely to have FOA (OR, 1.71; 95% CI, 1.24-2.36) compared with men. A BMI ≥30 kg/m2 was associated with increased odds of having FOA (OR, 1.76; 95% CI, 1.28-2.42) and increased odds of having SOA and FOA (OR, 1.85; 95% CI, 1.37-2.51). The presence of knee OA was associated with increased odds of having SOA only (OR, 1.79; 95% CI, 1.19-2.70), FOA only (OR, 1.78; 95% CI, 1.23-257), and both SOA and FOA (OR, 2.50; 95% CI, 1.78-3.52).
Prior back injury was found to be associated with SOA only (OR, 3.11; 95% CI, 1.09-8.91), and hip OA was associated with decreased odds of FOA only (OR, 0.69; 95% CI, 0.48-0.98). OA phenotypes were not significantly associated with low back pain severity or hand OA.
“[T]hese findings suggest the pathophysiologic processes may vary across different OA phenotypes in the lumbar spine. Increasing associations across categories of age suggest changes over time, however longitudinal studies may elucidate whether those with FOA only or SOA only remain an isolated lumbar SOA phenotype over time. In these analyses, race, sex, BMI, hip OA, and history of back injury may inform different OA phenotypes in the lumbar spine,” concluded the study authors.
Goode AP, Cleveland RJ, George SZ, et al. Demographic and clinical characteristics reflect different phenotypes of osteoarthritis in the lumbar spine: the Johnston County Osteoarthritis Project [published online May 6, 2019]. Arthritis Care Res. doi:10.1002/acr.23918