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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 63:629-634 (2008)
© 2008 The Gerontological Society of America

Racial Disparities in Receipt of Hip and Knee Joint Replacements Are Not Explained by Need: The Health and Retirement Study 1998–2004

Nicholas Steel, Allan Clark, Iain A. Lang, Robert B. Wallace and David Melzer

1 University of East Anglia, Norwich, United Kingdom.
2 Peninsula Medical School, Exeter, United Kingdom.
3 University of Iowa, Iowa City.

Address correspondence to Nicholas Steel, MBChB, MSc, School of Medicine, Health Policy and Practice, University of East Anglia, Earlham Road, Norwich, Norfolk, NR4 7TJ, United Kingdom. E-mail: n.steel{at}uea.ac.uk


   Abstract
Top
 Abstract
Methods
 Results
 Discussion
 References
 
Background. Hip and knee joint replacement rates vary by demographic group. This article describes the epidemiology of need for joint replacement, and of subsequent receipt of a joint replacement by those in need.

Methods. Data from the Health and Retirement Study were used to assess need for hip or knee joint replacement in a total of 14,807 adults aged 60 years or older in 1998, 2000, and 2002 and receipt of needed surgery 2 years later. "Need" classification was based on difficulty walking, joint pain, stiffness, or swelling and receipt of treatment for arthritis, without contraindications to surgery.

Results. Need in 2002 was greater in participants who were older than 74 years (vs 60–64: adjusted odds ratio 2.06; 95% confidence interval, 1.68–2.53), women (vs men: 1.81; 1.53–2.14), less educated (vs college educated: 1.27; 1.06–1.52), in the poorest third (vs richest: 2.20; 1.78–2.72), or obese (vs nonobese: 2.39; 2.02–2.81). One hundred sixty-eight participants in need received a joint replacement, with lower receipt in black or African American participants (vs white: 0.47; 0.26–0.83) or less educated (vs college educated: 0.65; 0.44–0.96). These differences were not explained by current employment, access to medical care, family responsibilities, disability, living alone, comorbidity, or exclusion of those younger than Medicare eligibility age.

Conclusions. After taking variations in need into consideration, being black or African American or lacking a college education appears to be a barrier to receiving surgery, whereas age, sex, relative poverty, and obesity do not. These disparities maintain disproportionately high levels of pain and disability in disadvantaged groups.

Key Words: Health care quality • Osteoarthritis • Arthroplasty • Health disparities • African Americans • Educational status

ARTHRITIS is a major cause of disability in North America and is responsible for considerable costs in health care and to society (1,2). The pain and disability caused by osteoarthritis can be cost-effectively treated with surgical replacement of the hip or knee joint (3–5). A hip or knee joint is replaced in 1% of the Medicare population annually, making arthroplasty the commonest noncoronary surgical intervention (6). Previous studies of access to joint replacement have shown that rates vary by race, sex, and education (7–9). However, need for surgery also varies with race, sex, and education (10–13), so variations in receipt can only be meaningfully interpreted when they take into consideration information about prior need for surgery.

Cross-sectional data on both need for and receipt of joint replacement in the English Longitudinal Study of Ageing showed variations in rates of hip or knee replacements by wealth, sex, and area of residence, but the sample did not have enough nonwhite participants to examine the effect of race (14). A Canadian regional study prospectively examined both need and receipt, but also had very few nonwhite participants (15). A recent study in the Department of Veterans Affairs system examined arthroplasty rates in those in need, but data on race were missing (16). No studies have prospectively examined both need and subsequent receipt of hip and knee joint replacements in a large, nationally representative, and racially diverse population.

We aimed to describe the epidemiology of need for hip and knee joint replacements in the Health and Retirement Study (HRS) in 1998–2002, and for those deemed in need, the epidemiology of receipt of a joint replacement over the subsequent 2 years. We aimed to examine the predictors of receiving a knee or hip joint replacement in those previously classified as being in need.


   METHODS
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 Abstract
 Methods
Results
 Discussion
 References
 
This study presents data from HRS on the prevalence of need for hip or knee joint replacement for the U.S. population 60 years old or older, and on the proportion of those in need who report having received joint surgery up to 2 years later. HRS is a longitudinal interview survey that collects data at 2-year intervals on more than 10,000 Americans older than 60 years (17). HRS is based on a stratified multistage area probability sample of U.S. households and includes oversamples designed to increase the numbers of Black and Hispanic participants (18).

All figures and analyses are based on the weighted sample, which adjusts for the overrepresentation of subpopulations within the HRS sample, so that the results are nationally representative. Included participants were 60 years old or older at the time of the surveys and reported no major contraindications to surgery. Contraindications to surgery were treatment for cancer, a chronic lung disease such as chronic bronchitis or emphysema (excluding asthma), stroke, or a heart attack or myocardial infarction in the past 2 years.

Participants in the 1998, 2000, and 2002 waves of HRS were classified as being in potential need of a hip or knee replacement if they reported disabling symptoms despite medical therapy. Participants were classified as in need if they responded ‘yes’ to all five of the following questions:

  1. Because of a health problem do you have any difficulty with walking several blocks?
  2. Do you sometimes have pain, stiffness, or swelling in your joints?
  3. Does your arthritis sometimes limit your usual activities?
  4. Have you had or has a doctor told you that you had arthritis or rheumatism?
  5. Are you currently taking any medication or other treatments for your arthritis or rheumatism?

These criteria are broadly consistent with the conclusions of the National Institutes of Health (NIH) consensus development panels that total hip replacement is an option for nearly all patients with diseases of the hip that cause chronic discomfort and significant functional impairment, and that candidates for elective total knee replacement should have moderate-to-severe persistent pain that is not adequately relieved by an extended course of nonsurgical management, and clinically significant functional limitation. The knee panel also recommended radiographic evidence of joint damage, which was not one of our criteria (19,20). Our definition of need is a clinically orientated population index that allows comparisons across diverse populations. It measures similar domains of self-rated pain and functional activity to those measured by other scoring systems for hip and knee disability (21–23).

For the analysis of receipt we formed a combined sample that was constructed from all those who were classified as being in need in 1998, plus all those newly in need in 2000 and 2002. Those in need were assessed to determine whether they had subsequently received a joint replacement in 2000, 2002, or 2004. Receipt was defined as reporting surgery or joint replacement of the hip or knee joint, because of arthritis, in the 2 years subsequent to classification as in need. Participants may have received more than one replacement joint. Replacements due to fracture were excluded as they are often emergency operations and have different etiology from elective replacements.

Data Analysis
Need for, and receipt of, arthroplasty were estimated in separate logistic regression models. The basic model included age, sex, and race as covariates, and the full model added obesity, education, and wealth. For the analysis of receipt only, an additional third regression model was fitted to explore the effect of the following factors: whether currently working, poor access to general medical care (had seen a doctor once or less in previous 2 years), family obligations (care for grandchild for >100 hours in previous 2 years), greater disability (difficulty walking 1 block), being married or cohabiting (vs being single, widowed, or divorced), and comorbidity (other than major diseases previously considered).

Participants described their race as primarily "White or Caucasian," "Black or African American," or "Other." Obesity was defined as a body mass index (BMI) of ≥30. BMI is weight (in kilograms) divided by height (in meters) squared. Participants were split into two groups by education level, depending on whether they had attended any college. Wealth was defined as total net household assets at the time of the interview. All analyses were carried out using survey tools in Stata SE 9.1 (StataCorp, College Station, TX).


   RESULTS
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 Abstract
 Methods
 Results
Discussion
 References
 
Epidemiology of Need
The characteristics of the sample and the distribution of need in the three waves—1998, 2000, and 2002—are given in Table 1 and Figure 1. Need was distributed similarly in all three waves, and was greater in participants who were older, female, black, poorer, or obese or who did not attend college. After adjustment for other factors in the full logistic regression model, need remained greater in those older than 74 years compared to those 60–64 years old (odds ratio [OR] 2.06; 95% confidence interval [CI], 1.68–2.53), in women compared to men (OR 1.81; 95% CI, 1.53–2.14), those who did not attend college compared to those who did (OR 1.27; 95% CI, 1.06–1.52), the poorest one third compared to the richest (OR 2.20; 95% CI, 1.78–2.72), and those with BMI of ≥30 (OR 2.39; 95% CI, 2.02–2.81) in 2002 (Table 2).


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  		Table 1. Sample Sizes and Distribution of Need for Hip or Knee Joint Replacement in 1998, 2000, and 2002.

 

Figure 01
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  		Figure 1. Need for hip or knee joint replacement in Health and Retirement Study (HRS) 1998–2002

 

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  		Table 2. Weighted Odds Ratios (OR) for Need of Hip or Knee Replacement in 1998, 2000, and 2002: Multivariate Logistic Regression.

 
The excess need in black participants was explained by obesity, education, and wealth in the full regression model in 2 of the 3 waves, 1998 and 2002. For example, in 2002 the OR for need in black compared to white participants dropped from 1.73 (95% CI, 1.43–2.09) in the basic model to 1.12 (95% CI, 0.91–1.38) in the full model. In 2000, the effect of race on need was only partially explained by the covariates, with the OR dropping from 2.20 (95% CI, 1.81–2.67) in the basic model to 1.44 (95% CI, 1.17–1.78) in the full model. There were no significant interactions between race and obesity or age.

Longitudinal Analysis of Receipt for Those in Need
The combined sample size from 1998, plus new participants in 2000 and 2002, was 14,807, of whom 1623 were classified as in need and 168 received a joint replacement within 2 years. The weighted basic logistic regression model of receipt in 2000, 2002, or 2004 for the combined sample showed significantly lower receipt for black participants compared to white (OR 0.46; 95% CI, 0.27–0.79), allowing for age and sex (Table 3, Figure 2). This lower receipt in blacks was not explained by the addition of any other factors to the model. When all factors were added in the additional third regression model, the OR for the effect of race was 0.34 (95% CI, 0.17–0.66).


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  		Table 3. Distribution of Receipt (in 2000, 2002, or 2004) of Hip or Knee Replacement for Those in Need (in the Combined 1998, 2000, and 2002 Sample), and Weighted Odds Ratio (OR) for Receipt: Multivariate Logistic Regression.

 

Figure 02
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  		Figure 2. Receipt of hip or knee joint replacement in Health and Retirement Study (HRS) 2000–2004, for those in prior need

 
Those without a college education were also less likely to have received surgery (OR 0.65; 95% CI, 0.44–0.96), with no change in the effect size in the third regression model (OR 0.65; 95% CI, 0.42–1.00). There was no significant interaction between race and college education. Receipt of a needed joint replacement did not vary with age, sex, wealth, obesity, or any other factors in the additional model.


   DISCUSSION
Top
 Abstract
 Methods
 Results
 Discussion
References
 
In this national study using longitudinal HRS data, we found significant disparities by race and education in receipt of needed hip or knee joint replacements. Participants describing themselves as black were only half as likely as white participants to have received a needed hip or knee joint replacement 2 years later. Those without a college education were one-third less likely to have received a needed joint replacement. These effects were not explained by age, sex, obesity, wealth, or other factors including current employment, access to general medical care, family responsibilities, disability differences, and comorbidity.

This article presents the first national comparisons of need for hip or knee replacement surgery between groups of U.S. residents. Our findings confirmed for the United States previous findings from Canada and the United States that need is greater in older adults, women, and those with low educational attainment (8,11,13,24). In addition, the results showed for the first time that age, sex, and education each have an independent effect on need and that the greater need in black participants was largely explained by education, wealth, and obesity. The estimated U.S. need of 7%–8% is slightly greater than a previous estimate of need in England of 5%–6%, using similar methods (14). This is consistent with previous findings about the poorer health of U.S. residents, but could be explained by the slightly broader definition of need used in this study compared to the study in England (25).

The data on receipt of joint replacement confirms, with a longitudinal analysis of national data, previous findings that joint replacement rates in the United States are lower for blacks than for whites, and higher for women than for men (7,9,26). Importantly, the restriction of the analysis of receipt to those in need shows for the first time that the greater receipt in women, older people, and the more obese, is appropriate for their greater need but that the lower receipt by black participants occurs despite their level of need. The lower receipt by black participants is not explained by a wide range of biological and social factors.

This study has a number of strengths. The stratified multistage sampling used by HRS, and the large number of participants of different races, means that the findings are representative of the population of the United States. HRS includes a broad range of quality-controlled data, including detailed direct estimates of socioeconomic status, comorbidities, and both social and health information. This allows both need and subsequent receipt of hip or knee joint surgery to be estimated on the same sample, allowing for the effects of covariates.

Limitations of the study include the fact that the classification of need relies on self-reported pain, disability, and treated arthritis. Assessment of need for joint surgery was not the primary objective of HRS, which does not include a measure of pain and physical functioning directly attributable to the hip or knee joint. The definition of need would have been stronger if it included such a measure, preferably together with radiological and skilled clinical examination to assess the degree of pain and attribute symptoms to the hip or knee joint. However, there are no completely satisfactory clinical criteria for hip or knee replacement, and radiographic appearance correlates poorly with disease (27–30). The figures for prevalence of need in this article should be used solely to compare relative need in different groups of participants, and not to estimate absolute need for surgery at individual or population level.

The effects are not explained by eligibility for Medicare insurance coverage, as a sensitivity analysis excluding those 60–64 years old showed very similar effect sizes to the analysis including this group. Those with major comorbidities were excluded from the analysis, and other minor comorbidities were included in the regression model, so comorbidity is unlikely to be an explanation for the results. Many joint replacements occur in people not in ‘need’: some will have an acute onset, and others will be the result of fracture secondary to osteoporosis rather than osteoarthritis. Those not in "need" were excluded from the analysis of receipt.

Our clinical measure of need does not include cultural variations in willingness to consider surgery, which was found to be a strong predictor of future joint replacement in a Canadian cohort, where it explained the effect of education (15). African American and ethnic minority patients are less willing than are white patients to undergo joint replacement, and this may account for our findings (31–33). Differences in willingness are explained by different expectations of treatment and subsequent symptoms, and so may be influenced by education about arthritis (15,31).

There are other possible explanations for our findings. Arthritis-specific health beliefs vary little by race, but the important role of faith in African Americans' expectations of care may contribute to lower access to surgery (34,35). The views of referring practitioners on the characteristics of patients likely to benefit from hip replacement influence referral rates, and may act as a barrier (36). Further research is needed into the mechanism by which race and low education are associated with low rates of joint replacement for those in need, and specifically into whether educational interventions can alter willingness to consider surgery and rates of joint replacement.


   Acknowledgments
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 Abstract
 Methods
 Results
 Discussion
 References
 
The Health and Retirement Study is sponsored by the National Institute on Aging (grant U01AG009740) and conducted by the University of Michigan. N.S. was supported by a Primary Care Researcher Development Award from the UK National Coordinating Centre for Research Capacity Development.


   Footnotes
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 Methods
 Results
 Discussion
 References
 
Decision Editor: Luigi Ferrucci, MD, PhD

Received March 13, 2007

Accepted September 12, 2007


   References
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 Abstract
 Methods
 Results
 Discussion
 References
 

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