Hip and knee osteoarthritis (OA), but not hand OA, increase the risk of cardiovascular (CV) events, and this risk is higher with a greater number of hips and knees affected, Canadian researchers have found.

In their population-based cohort study, the risk of CV events was 13% higher among OA patients with at least two hips/knees involved compared with none, increasing to a 22% greater risk with three or more hips or knees affected, reported Tetyana Kendzerska, MD, from the University of Ottawa in Canada, and co-investigators.

“The absolute effect of having at least three hip/knee joints with OA was comparable to the effects of obesity or hypertension on risk for subsequent CV events,” they wrote in Osteoarthritis and Cartilage. “This relationship became non-significant when we further controlled for difficulty walking at baseline. Self-reported difficulty walking was associated with a 30% increased hazard of CV events development controlling for confounders.”

Study participants were obtained from the Ontario Hip and Knee Cohort. Included were 18,490 adults 55 years and older (median age 68), 1,856 of whom met criteria for hip OA, 2,830 of whom met criteria for knee OA and 2,961 for hand OA. Some 60.3% were female and the median body mass index of the entire cohort was 25.5. Limitation in grip and walking were reported by 16% and 25%, respectively.

Over a median follow-up of 13.4 years, 5,898 (31.9%) individuals experienced one or more CV events, which included 2,759 hospitalizations for congestive heart failure, 1,865 for myocardial infarction, 1,844 for stroke, 1,344 for angina and 1,238 for a cardiac revascularization procedure.

In unadjusted analyses, individuals with OA in knee or hip, but not hand, were significantly more likely to experience a CV event compared with those with no hip/knee involvement.

Adjusted hazard ratios for involvement of two hips/knees versus none was 1.13 (95% CI 1.03-1.23) and for three or more hips/knees, 1.22 (95% CI 1.09-1.36). After adjusting for each of age, BMI, sex, metabolic factors, and covariates other than walking limitation, the relationship between hip/knee OA and CV events was only modestly attenuated.

Further adjustment for difficulty walking attenuated these relationships, such that they became non-significant — thereby suggesting that this mobility impairment drove the overall results.

Indeed, self-reported difficulty walking was associated with a 30% increased hazard of CV events (adjusted HR 1.30, 95% CI 1.23-1.38).

In the fully adjusted model, the presence of hip or knee OA was associated with a 10% increase in the risk of CV events (HR 1.10, 95% CI 1.01 to 1.18). The entire effect of knee/hip OA on excess CV risk was mediated by difficulty walking, as evidenced by a direct HR of 0.98 and an indirect HR of 1.12.

A clinical nomogram showed that the effects of three or more hip/knee joints with OA was comparable to the effects of obesity and hypertension on CV risk. In the case of a hypothetical 65-year-old woman with hypertension and diabetes, without CV disease and with three or more hip/knee joints with OA, her 10-year, event-free survival was estimated at 60%-70%, which is 10% worse than the same woman with the same risk factors but without hip or knee OA.

“Our findings of a dose-effect relationship between number of hips and knees with OA and CV risk after rigorously controlling for CV risk factors, and attenuation of the relationship after controlling for walking difficulty, lend strong support for a causal relationship between OA and CV disease that is explained, at least in part, by OA-related mobility,” they wrote.

“The strength of the relationship between our simple measure of walking difficulty and CV events suggest its potential usefulness in clinical practice.”

As a study limitation, the authors mentioned the potential for unmeasured confounders, such as lipid values, the use of nonsteroidal anti-inflammatory drugs and smoking. Also, changes in OA symptom severity were not controlled for and the presence of walking difficulty was based on self-report.

• Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner