- Top of page
- MATERIALS AND METHODS
- AUTHOR CONTRIBUTIONS
Arthritis is a major public health problem, with estimated costs due to health care and lost productivity between 1–2% of the gross domestic product (1). At the individual level, people with arthritis incur higher health-related costs (2) and have worse quality of life than the general population (3). Monitoring the population's prevalence of arthritis is an important part of developing strategies to reduce the impact of this condition because it identifies population groups that may benefit from interventions.
In clinical practice, the diagnosis of arthritis is based on a combination of clinical assessment (history and physical examination) and radiographic and laboratory data (4–6). Given that detailed clinical investigations are costly and time consuming, alternative methods of identifying arthritis cases in population health surveys are still evolving. Prior to the mid 1990s, the identification of arthritis cases in population-based surveys was generally through self-report of one of the conditions classified as arthritis in the International Classification of Diseases, Ninth Revision (ICD-9) (7–10). However, this definition was found to be unreliable. In a survey of 472 rheumatology outpatients that assessed the concordance between ICD-9 based self-reported rheumatic conditions and diagnosis by physician, nearly one-third of respondents were unable to report their condition correctly (11).
As a result, guidelines by the US Centers for Disease Control and Prevention (CDC) recommended that the case definition of arthritis change from self-reported arthritis to self-report of having been diagnosed with arthritis by a health professional (12–14). Concurrently, the CDC introduced a question about the presence of chronic joint symptoms of pain, aching, and stiffness on most days for at least a month to try to capture those people with arthritis who had not consulted a health care professional. Those who had either self-reported doctor-diagnosed arthritis or chronic joint symptoms were classified as cases of arthritis. The approach of combining self-reported doctor-diagnosed arthritis and chronic joint symptoms, however, produced estimates of arthritis prevalence that have varied substantially over time (30% in 1996, 24% in 1997, and 33% in 2001) (15). Consequently, the CDC Arthritis Program issued an amended recommendation that self-reported doctor-diagnosed arthritis and chronic joint symptoms should not be combined into a single indicator, but that chronic joint symptoms should be used as an indicator of possible arthritis (16).
The prevalence of chronic joint symptoms has been estimated at 10% of the adult population (15, 16). However, the health service implications of identifying individuals with chronic joint symptoms are poorly understood because information on the impact of this condition on health, activity limitations, and health-related quality of life (HRQOL) is limited. It has also been reported that a substantial proportion of people who have chronic joint symptoms do not have arthritis on clinical examination (17, 18). These findings have given rise to concerns that people with transient joint symptoms (defined as the experience of joint pain, aching, stiffness, or swelling but not on most days for the past month), resulting from joint injury, for example, may be misclassified as cases of possible arthritis (19). Therefore, a better understanding of the prevalence and impact of both chronic and transient joint symptoms is warranted.
The aims of this study were to estimate the prevalence and co-occurrence of self-reported doctor-diagnosed arthritis, chronic joint symptoms, and transient joint symptoms, and to compare demographic and socioeconomic characteristics, activity limitations, and the HRQOL of individuals with joint problems (self-reported doctor-diagnosed arthritis or chronic or transient joint symptoms) with those who have no self-reported doctor-diagnosed arthritis and no joint symptoms.
- Top of page
- MATERIALS AND METHODS
- AUTHOR CONTRIBUTIONS
Using the 2004 population-based South Australian Health Omnibus Survey, we determined both the prevalence and impact of self-reported doctor-diagnosed arthritis, chronic joint symptoms, and transient joint symptoms in the general population. The prevalence of joint problems was high, with 50% of participants reporting either joint symptoms or self-reported doctor-diagnosed arthritis. Of the respondents, 11% had chronic joint symptoms, 13% had transient joint symptoms, and approximately one-quarter (26%) reported having a prior diagnosis of arthritis. Chronic joint conditions (chronic joint symptoms and self-reported doctor-diagnosed arthritis) accounted for 74% of all joint problems. Increased likelihood of transient joint symptoms was associated with being 45–54 years old and having a BMI in the obese range. The presence of chronic joint symptoms was associated with being 45–64 years old and having a BMI in the obese range. The frequency of self-reported doctor-diagnosed arthritis greatly increased with age and was higher among women and those who had a BMI in the overweight or obese range. Although on average transient joint symptoms were not associated with poor HRQOL, people with transient joint symptoms were more limited in bending, kneeling, or stooping than those who had no joint problems. People who had either chronic joint symptoms or arthritis were more likely to have activity limitations and worse HRQOL than people with no joint problems or people with transient joint symptoms. The self-reported doctor-diagnosed arthritis group experienced the most activity limitations and the poorest HRQOL. These findings address an important gap in previous research by providing information on the population groups with various types of joint problems and the consequences of each on daily function and HRQOL.
Our prevalence estimates of 13% for transient joint symptoms, 11% for chronic joint symptoms, and 26% for self-reported doctor-diagnosed arthritis among Australian adults interviewed face-to-face are similar to the results from the US Behavioral Risk Factors Surveillance System. Using a similar set of screening questions in a telephone interview, this survey estimated that 12%, 10%, and 23% of US adults have transient joint symptoms, chronic joint symptoms, and self-reported doctor-diagnosed arthritis, respectively (30). Although the characteristics of people with joint pain have been previously assessed in several studies (31–33), only a few studies simultaneously examined the distribution of chronic joint symptoms and self-reported doctor-diagnosed arthritis across population groups (16, 30, 34), with conflicting results. Virtually all such studies were conducted in the US, with consistent reports that increased prevalence of self-reported doctor-diagnosed arthritis was associated with older age, female sex, and low socioeconomic status. However, findings about the characteristics of people with chronic joint symptoms are less consistent. In some investigations, people with chronic joint symptoms did not differ from those who had no joint problems on age, sex, or educational attainment (30, 34), whereas in other investigations, higher frequency of chronic joint symptoms was associated with being <65 years of age and male (16). In our study, chronic joint symptoms were most frequent among people ages 45–64 years old, after controlling for sex, area of residence, education, occupation, income, and BMI. Direct comparisons of the chronic joint symptoms group with those who had transient joint symptoms and self-reported doctordiagnosed arthritis also showed that people with chronic joint symptoms had less education and higher BMI than people with transient joint symptoms, and were generally younger and had higher incomes than those who had self-reported doctor-diagnosed arthritis.
However, it is important to note that our study is based on a probability sample of Australian households, with data collected in face-to-face interviews. One of the previous US-based studies (34) was conducted with a probability sample of 851 Chicago-area residents ages ≥45 years. Other studies were based on probability samples of the US general population ages ≥18 years (16, 30) with data collected in telephone interviews. Because different sampling and data collection methods systematically exclude certain population groups (for example, the homeless, and people without a telephone), differences in the findings between our study and past studies may reflect the study designs rather than real differences in the distribution of chronic joint symptoms between population groups in Australia and the US.
Previous studies have identified high BMI as a risk factor for arthritis and chronic joint pain (30, 33, 35). The results of our study extend previous findings by showing that having a BMI in the obese range is associated with increased likelihood of transient joint symptoms, even after controlling for the effects of age, sex, and socioeconomic status. In addition, people with a BMI in the obese range may be more likely to have chronic joint symptoms rather than transient joint symptoms. Although the cross-sectional design of this study does not allow conclusions about the causal relationship between BMI and joint problems, longitudinal evidence suggests that people with excess weight are at a higher risk for arthritis later in life (36, 37).
A substantial body of literature documents the high personal burden of arthritis, with adverse impacts on health and functioning (38–40). Chronic musculoskeletal pain is also associated with disturbed sleep (41) and depression (42). The high morbidity among people with chronic joint symptoms in our study further suggests that this population group may benefit from intervention programs directed at preventing additional disability. Our results also indicate the progressive increase in activity limitations and the decline in HRQOL among the joint conditions studied, beginning with transient joint symptoms, chronic joint symptoms, and self-reported doctor-diagnosed arthritis. This suggests that these groups may represent a severity continuum of underlying joint pathology. Our finding that the prevalences of both transient and chronic joint symptoms decrease with age, whereas the prevalence of self-reported doctor-diagnosed arthritis increases with age, provides some support for this hypothesis. However, longitudinal studies are needed to explore the possibility of conversion from transient to chronic joint symptoms and from chronic joint symptoms to arthritis.
The risk of activity limitations in chronic musculoskeletal conditions is well documented (8, 43, 44). Several studies have also linked functional impairment with increased BMI (45, 46), with evidence to suggest that a high BMI predates the development of activity limitations in people with joint pain (40). A recent meta-analysis of randomized controlled trials also reported a decrease in physical disability among overweight patients with knee osteoarthritis after a weight reduction program (47). Exercise and weight loss have therefore become an important part of arthritis treatment and management (48, 49). However, our study also shows that the presence of joint problems is a strong risk factor for activity impairment independent of BMI. This finding has important implications for arthritis management. Similarly, although weight loss and exercise programs for people with a range of chronic conditions can improve overall health status and reduce the risks of heart disease and diabetes mellitus, mobility limitations experienced by those with concurrent joint problems, including difficulties with walking, bending, and climbing stairs, need to be taken into consideration when designing and implementing these programs.
Information on arthritis prevalence, with detailed information on the specific limitations that people with this condition experience, highlights the extent and nature of the arthritis burden, and supports health service program planning and the design of interventions to prevent and reduce arthritis-related disability. However, a limitation of our study was the lack of clinical assessment to verify self-reported arthritis diagnosis and to determine the underlying pathology of joint symptoms. Previous studies have shown that the estimates of the prevalences of painful musculoskeletal conditions are greatly influenced by the method of case definition (42, 50). The validity of chronic joint symptoms as an indicator of possible arthritis has been examined in a limited number of studies (17, 18), with results suggesting that only ∼60% of people ages 45–64 years who meet the case definition for chronic joint symptoms have some form of arthritis on clinical examination. The accuracy of chronic joint symptoms as an indicator of arthritis was reported to increase with age, with 90% of individuals with chronic joint symptoms having clinically confirmed arthritis at ages ≥65 years. Although no comparable data are available for individuals ages <45 years, this suggests that using chronic joint symptoms as an indicator of arthritis overestimates its prevalence, especially among younger individuals.
Therefore, to better understand the implications of identifying individuals with chronic joint symptoms for health care services, future studies are needed to investigate the relevant clinical outcomes and sequela of chronic joint symptoms. Despite the uncertainty about pathology of chronic joint symptoms, the results of this study also suggest that this indicator identifies individuals with compromised health and well-being, therefore providing potentially valuable information for health care planners. A more detailed understanding of people's behavior and capacity to engage in exercise programs while living with chronic joint conditions will support the development of more focused primary and secondary prevention programs.
A limitation of this study was a relatively low response rate (66%), which could potentially jeopardize the external validity of the results. However, because the survey data were weighted by age, sex, and geographic area, the impact of nonresponse on generalizability is expected to be minimal.
The results of this study document the high prevalence and impact of joint conditions in the community. Although clinical investigations are required to confirm the validity of chronic joint symptoms as an indicator of possible arthritis, the chronic joint conditions studied here are substantial barriers to effective public health interventions aimed at reducing primary and secondary risk factors such as obesity and inactivity. With the aging population, increasing obesity rates, and declining physical activity, arthritis prevalence is likely to increase and impede individuals' ability to participate in the work force, fulfill career roles, and be active members of the community more generally.