Higher Weight-Adjusted Waist Index Tied to Greater Mortality Risk in Patients With Osteoarthritis

Elevated weight-adjusted waist index (WWI) levels are associated with increased all-cause and cardiovascular mortality among patients with osteoarthritis, according to a study published in BMC Musculoskeletal Diseases.1

Osteoarthritis is being increasingly recognized for its association with elevated mortality rates. It frequently occurs alongside other chronic conditions, such as diabetes and obesity, which may increase the risk of early mortality.

Patients with osteoarthritis, especially those with obesity, have a higher mortality rate due to their systemic inflammatory status, comorbidities, and mobility limitations. Because of this, the researchers emphasized the need to understand the relationship between osteoarthritis and mortality to enhance clinical management and develop strategies to mitigate the long-term health risks of the disease.

Although obesity is well established as a major factor influencing the pathogenesis and prognosis of osteoarthritis, current obesity measures fail to reflect changes in muscle mass and body composition in this population. Instead, the researchers recommended using WWI, which integrates waist circumference measurement to emphasize abdominal obesity, providing a more precise assessment of muscle quality and fat distribution.2

WWI has been linked to the onset of osteoarthritis, but no studies have investigated its impact on the survival outcomes in this population.1 To address this gap, the researchers evaluated the association between WWI and all-cause and cardiovascular mortality among patients with osteoarthritis within the National Health and Nutrition Examination Survey (NHANES), spanning 2005 to 2018.

Researchers consider the weight-adjusted waist index (WWI) as a more precise predictor of mortality risk in patients with osteoarthritis than traditional obesity measures, like body mass index. | Image Credit: fotoduets - stock.adobe.com

They only included patients who self-reported being diagnosed with osteoarthritis. Also, WWI was calculated for each patient by dividing waist circumference (in cm) by the square root of weight (in kg). Then, participants were grouped into WWI tertiles (Q1, Q2, and Q3), with a higher score and tertile indicating a higher degree of obesity.

The primary outcomes of all-cause and cardiovascular mortality were assessed with mortality data from the National Death Index as of December 31, 2019. The researchers classified and coded all causes of death according to the International Classification of Diseases, Tenth Revision (ICD-10). Similarly, cardiovascular mortality was defined using relevant ICD-10 codes.

They used Kaplan-Meier survival curves and Cox proportional hazards regression models to assess the association between WWI and mortality outcomes among this population. Also, the dose-response relationship was evaluated using a restricted cubic spline model.

Additionally, they conducted subgroup analyses to determine if various sociodemographic, lifestyle, and comorbid factors, such as age, gender, race, hypertension, and obesity, were associated with the primary outcomes.

Of the 70,190 participants involved in NHANES from 2005 through 2018, the researchers included 3554 eligible patients in their final analysis. Among these patients, 41% were over the age of 65, and most were female (64% vs 36%) and non-Hispanic White (83%). During the follow-up period, 661 patients died (13%), with 26% of deaths attributed to cardiovascular causes.

Deceased individuals were more likely to be older (P < .001) and of non-Hispanic White ethnicity (P = .007) than survivors. In contrast, survivors had significantly lower WWI values and a lower classification within WWI tertiles than deceased individuals. The 2 groups also exhibited significant differences in obesity rates and the prevalence of comorbidities, including hypertension and diabetes (both P < .001).

The researchers used 3 Cox regression models to examine the independent association between WWI and both all-cause and cardiovascular mortality; model 1 was unadjusted, model 2 minimally adjusted for covariates, and model 3 was fully adjusted. Model 1 found a significant positive association between WWI and all-cause mortality (HR, 1.74; 95% CI, 1.51-2.00; P < .001), which remained significant in both models 2 (HR, 1.39; 95% CI, 1.19-1.63; P < .001) and 3 (HR, 1.28; 95% CI, 1.07-1.52; P < .001).

When stratified by WWI tertiles, the researchers observed similar results. In all 3 models, patients in the highest tertile had an increased risk of all-cause mortality compared with those in the lowest tertile (model 1: HR, 2.91; 95% CI, 2.29-3.69; model 2: HR, 1.94; 95% CI, 1.49-2.53; model 3: HR, 1.66; 95% CI, 1.25-2.20; all P < .001).

For cardiovascular mortality, they found that both WWI and WWI tertiles were significantly positively associated with mortality in models 1 and 2. However, in model 3, the association was not significant.

Restricted cubic spline models demonstrated a linear positive association between WWI and all-cause (P for nonlinear = .224) and cardiovascular (P for nonlinear = .776) mortality. In addition, Kaplan-Meier curves found significant differences in survival patterns across WWI tertiles, with higher tertiles associated with an increased risk of both all-cause and cardiovascular mortality (both P < .001).

Lastly, a positive correlation between WWI and all-cause mortality was observed across all subgroups. A similar trend was seen for cardiovascular mortality in most subgroups. Therefore, the effect of WWI on all-cause and cardiovascular mortality in patients with osteoarthritis was robust across subgroups, with no substantial influence from the covariates.

The researchers acknowledged their study’s limitations, including its observational nature. Because of this, it cannot establish a causal relationship between WWI and mortality in these patients with osteoarthritis. Despite the limitations, they expressed confidence in their findings.

“The results suggest that WWI measurement may aid in mortality and prognostic prediction for OA [osteoarthritis] patients and support strategies for managing and controlling obesity in this population,” the authors concluded.

References

1. Guo S, Chen D, Zhang Y, Cao K, Xia Y, Yang D. Association of weight-adjusted waist index with all-cause and cardiovascular mortality in individuals with osteoarthritis. BMC Musculoskelet Disord. 2025;26(1):390. doi:10.1186/s12891-025-08638-4
2. Park Y, Kim NH, Kwon TY, Kim SG. A novel adiposity index as an integrated predictor of cardiometabolic disease morbidity and mortality. Sci Rep. 2018;8(1):16753. doi:10.1038/s41598-018-35073-4