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Edmonton Obesity Scoring System

Scoring system predicts risk of death for bariatric patients

Scoring system improves on current methods by observing risk factors
Researchers claim BMI is insufficient as it does not directly consider obesity-related comorbidities

Researchers from the University of Alberta claim that their risk assessment scoring system, the Edmonton obesity staging system (EOSS), improves on current methods in helping to predict the risk of death in overweight and obese people. The study has been published in the Canadian Medical Association Journal.

According to the researchers, anthropometric-based classification schemes for excess adiposity (such as BMI) do not include direct assessment of obesity-related comorbidity and functional status, and cannot distinguish between lean and fat tissue. Therefore, BMI has limited clinical utility. 

The EOSS, originally proposed by Dr Arya Sharma from the University of Alberta, ranks overweight and obese people on a five-point scale according to their underlying health status and the presence or absence of underlying health conditions. It is a clinical staging system that ranks people with excess adiposity on a five-point ordinal scale, while incorporating obesity-related comorbidities and functional status into the assessment.

The scoring system is as follows:

  1. No apparent risk factors (e.g., blood pressure, serum lipid and fasting glucose levels within normal range), physical symptoms, psychopathology, functional limitations and/or impairment of well-being related to obesity.
  2. Presence of obesity-related subclinical risk factors (e.g., borderline hypertension, impaired fasting glucose levels, elevated levels of liver enzymes), mild physical symptoms (e.g. dyspnea on moderate exertion, occasional aches and pains, fatigue), mild psychopathology, mild functional limitations and/or mild impairment of well-being.
  3. Presence of established obesity-related chronic disease (e.g., hypertension, type 2 diabetes, sleep apnea, osteoarthritis), moderate limitations in activities of daily living and/or well-being.
  4. Established end-organ damage such as myocardial infarction, heart failure, stroke, significant psychopathology, significant functional limitations and/or impairment of well-being.
  5. Severe (potentially end-stage) disabilities from obesity-related chronic diseases, severe disabling psychopathology, severe functional limitations and/or severe impairment of well-being
EOSS has previously been used to predict death using data from a population-representative survey of 8,143 people in the 1988-1994 and 1999-2004 US National Health and Human Nutrition Examination Surveys (NHANES).

In this latest study, researchers undertook a rigorous examination of EOSS and assessed its ability in predicting mortality independent of anthropometric indices in a large, nationally representative US sample.

The investigators analysed data from NHANES III (1988–1994) and the NHANES 1999–2004, with mortality follow-up through to the end of 2006. Adults (aged over 20) with overweight or obesity who had been randomised to the morning session at the mobile examination centre were scored according to the Edmonton obesity staging system.

They examined the relationship between staging system scores and mortality, and Cox proportional hazards models were adjusted for the presence of the metabolic syndrome or hyper-triglyceridemic waist (waist circumference ≥90cm and a triglyceride level ≥ 2mmol/L for men; and ≥85cm and ≥1.5mmol/L for women).

More than 75% of the cohort with overweight or obesity were given scores of 1 or 2. Scores of 4 could not be reliably assigned because specific data elements were lacking. The survival curves clearly diverged when stratified by scores of 0–3, but not when stratified by obesity class alone.

Within the data from the NHANES 1988–1994, scores of 2 (hazard ratio [HR] 1.57; 95% confidence interval [CI] 1.16 to 2.13) and 3 (HR 2.69; 95% CI 1.98 to 3.67) were associated with increased mortality compared with scores of 0 or 1, even after adjustment for body mass index and the metabolic syndrome. The researchers found similar results after adjusting for hypertriglyceridemic waist, as well as in a cohort eligible for bariatric surgery. 

The study found that within a nationally representative cohort, higher EOSS scores were a strong predictor of increasing mortality in both the overall population and in a cohort of people eligible for bariatric surgery, independent of BMI and the presence of metabolic syndrome or hypertriglyceridemic waist. Moreover, even within strata of BMI categories, there was clear separation of survival curves (Figure 2), the authors noted.


Figure 2: Comparison of staging system and anthropometric classification scheme for predicting all-cause mortality among people with overweight and obesity.


Despite the results from the study, the authors do acknowledge that the study does have some limitations. For example,  comorbidities were arbitrarily assigned to be equivalent in terms of their burden of illness although it is not yet clear whether certain comorbidities should receive a higher weighting. Moreover, the researchers made no distinction between types of diabetes (of Americans with diabetes, 90%–95% have type 2 diabetes). However, both subtypes would require management in an overweight or obese cohort and were thus judged appropriate for inclusion. 


Nevertheless, the investigators concluded that the EOSS is a strong predictor of increasing mortality independent of BMI, metabolic syndrome and hypertriglyceridemic waist. It independently predicted increased mortality even after adjustment for contemporary methods of classifying adiposity. 

The authors proposed that this system should  be considered adjunctive to current anthropometric classification systems in assessing obesity-related risk, determining prognosis and guiding potential bariatric surgery treatment options.

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