Hip Osteoarthritis Linked to Increased Mortality

Janis C. Kelly

March 25, 2015

Older women with radiographically apparent hip osteoarthritis (RHOA) had significantly higher all-cause mortality and cardiovascular disease (CVD) mortality than similar women who did not have RHOA, according to a large, population-based cohort study.

Specifically, RHOA was associated with 43% of the increase in all-cause mortality and with 25% of the increase in CVD mortality, report Kamil E. Barbour, PhD, MPH, epidemiologist with the arthritis program at the Centers for Disease Control and Prevention's (CDC's) Division of Population, Atlanta, Georgia, and colleagues in an article published online March 10 in Arthritis & Rheumatology. The researchers suggest that physical function and lack of physical activity resulting from RHOA contribute to the increased mortality risk.

"Increased physical activity is associated with improved physical function, and there is a wealth of literature that implicates poor function as a risk factor for mortality," Dr Barbour told Medscape Medical News. "This is especially imperative because physical activity levels in adults with osteoarthritis are low (about 1 in 10 meet [US Department of Health and Human Services] physical activity recommendations of 150 min/week). Clinicians should recommend physical activity interventions for their patients with OA. The CDC recommends various evidence-based physical activity and self-management interventions that have been shown to improve function."

Yuqing Zhang, DSc, professor of medicine/epidemiology at the Boston University School of Medicine Clinical Epidemiology Research & Training Unit in Massachusetts, who was not involved in the study, told Medscape Medical News that the findings are interesting and that other studies have found an association between symptomatic knee/hip OA and all-cause mortality.

"The authors are to be applauded for exploring several potential biological mechanisms through which hip ROA may affect all-cause as well as cause-specific mortality, using novel statistical methods; ie, mediation analysis," Dr Zhang said. "The results suggest that an increased all-cause mortality and CVD mortality from hip ROA is mainly through its effect on physical function (42.9% vs 25%, respectively). These findings will not only shed light on our understanding of the pathophysiology of hip ROA and mortality but also provide healthcare providers with potential evidence-based interventions for reducing mortality to individuals with hip OA."

Analysis Included Nearly 8000 Women With Hip OA

Dr Barbour and colleagues designed the study to determine the risk for all-cause and disease-specific mortality among older women with hip OA. The researchers also worked to identify factors that might mediate that pathway linking hip OA and mortality.

The analysis was based on data from the Study of Osteoporotic Fractures, which included 9704 white US women older than 65 years. Hip radiographs were available for 7889 women at baseline and for 5749 women at year 8. The researchers used death certificates and hospital discharge summaries to confirm mortality; they defined RHOA as Croft grade 2 or worse (joint space narrowing or osteophytes plus one other radiographic feature) in at least 1 hip. Potential mediators included in the analysis were physical activity, objectively measured physical function, disability, hip pain, and nonsteroidal anti-inflammatory drug use.

The researchers found that RHOA prevalence was 8.0% at baseline and 11.0% at year 8. With a mean follow-up time of 16.1 years, the cumulative mortality incidence was 67.7% for all-cause mortality, 26.3% for CVD mortality, and 11.7% for cancer mortality.

After multivariate analysis adjusted for age, body mass index, education, smoking, health status, diabetes, and stroke, RHOA was associated with significantly increased risk for all-cause (hazard ratio [HR], 1.14; 95% confidence interval [CI], 1.05 - 1.24) and CVD (HR, 1.24; 95% CI, 1.09 - 1.41) mortality, but not for mortality resulting from cancer, gastrointestinal disease, or other causes.

Study Showed OA Affects Mortality, Not Just Morbidity

"OA is primarily thought of as a condition that is linked to morbidity, but our study showed that having it can increase your risk of all-cause and CVD mortality," Dr Barbour said. "Furthermore, not addressing poor physical function in those with OA may result in an increased risk of the above-mentioned mortality outcomes."

The mediation analysis showed that physical function accounted for about 43% of the increased risk for all-cause mortality and 25% of the increased risk for CVD mortality. Dr Barbour said, "In our study, hip OA was an independent risk factor for CVD mortality, and the association was mediated by physical function. In other words, a large portion of the increased risk of mortality in those with hip OA was attributed to their poor physical function."

Total Hip Replacement Might Have a Protective Effect

Interestingly, when the researchers restricted their analyses to those adults with RHOA who had not had a hip replacement, the hazard ratios for all-cause mortality and CVD mortality increased beyond what those for the entire RHOA population (HR for all-cause mortality, 1.24 vs 1.14; HR for CVD mortality, 1.24 vs 1.30, respectively). Dr Barbour said, "The reason for the apparent protective effect is not clear, but several studies, including ours, point towards a decreased risk of mortality in those with [total hip replacement] compared with those without. Some surmise that it is due to those with [total hip replacement] being healthier than the population they are compared with, but this was not the case in our study. Having [total hip replacement] surgery would result in improved function in most cases, and we showed that function is linked to mortality via hip OA."

The study authors and Dr Zhang have disclosed no relevant financial relationships.

Arthritis Rheum. Published online March 10, 2015. Abstract

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