Risk factors for arthritis: a new addition?

Arthritis is widely recognised as a common and often debilitating disease.¹ In developed countries, it is the single most common cause of disability.² The term ‘arthritis’ includes more than 100 different diseases and conditions, the most common of which are osteoarthritis and rheumatoid arthritis (RA).³

Arthritis is a growing public health problem in Ireland because of its high prevalence and its associated high socioeconomic costs. Studies have shown that people with arthritis experience a lower quality of life compared to those without arthritis.³ Targeting specific at-risk populations offers the potential to reduce the incidence of arthritis onset and to slow the progression of already established disease. 

Ireland – the arthritis picture

More than one in five Irish people suffer with some form of arthritis.³ This equates to approximately 915,000 people living with arthritis in Ireland.³ Eighteen per cent of these are under 55 years of age. Although treatments are continuing to improve, no cure for arthritis currently exists. Every year, approximately 400,000 people attend their doctor with symptoms related to arthritis.⁴ Almost one-third of women and one-quarter of men will complain of arthritis or joint pain to their GP, accounting for the largest category of GP visits.⁴ Approximately 60% of people with arthritis will be treated within primary care.⁴

However, a proportion will require referral onto specialist tertiary centres. The most common cause of work-related ill health in Ireland is musculoskeletal disorders, of which arthritis sufferers make up a large proportion. It is estimated that arthritis costs the state €1.6 billion in terms of lost working hours annually.³

Risk factors for arthritis

In order to reduce the incidence of arthritis in Ireland, identifying risk factors is key. Targeting these could have huge cost-saving benefits. Risk factors vary according to the type of arthritis. Osteoarthritis is traditionally ‘wear and tear’ arthritis and risk factor modification is crucial. 

Non-modifiable risk factors include age, gender and genetics.⁵ The risk of developing most types of arthritis is increased with age. Women suffer from arthritis more commonly than men. There are genetic factors associated with increased risk of certain types of arthritis, eg. RA, systemic lupus erythematosus (SLE) and ankylosing spondylitis (AS).⁵

However, there are many modifiable risk factors that health professionals can target to reduce the risk of arthritis. Obesity can contribute to the onset and progression of knee osteoarthritis. A previous joint injury or infection can contribute to the development of arthritis. There are links between occupation and osteoarthritis, eg. occupations involving repetitive knee bending and squatting.⁵ Sedentary lifestyle has also been shown to increase the risk of osteoarthritis.

Prevalence in socially disadvantaged areas

A potential new risk factor was recently identified in research carried out in Australia. Results of an Australian study accepted for publication in the Arthritis Care and Research journal have revealed some thought-provoking questions about location of residence as a risk factor for arthritis.¹

The study was carried out by researchers from the University of Melbourne, Deakin University and Queensland University of Technology. Data were extrapolated from the HABITAT (How Areas in Brisbane Influence Health and Activity) cohort, a multi-level longitudinal study of physical activity among adults aged between 40 and 65 living in Brisbane.¹ Over 10,000 males and females from 200 neighbourhoods of varying socioeconomic status were surveyed by questionnaire in 2007. The neighbourhoods were defined by the Australian Bureau of Statistics as 200 dwellings in a suburb that were relatively homogeneous in terms of their socioeconomic characteristics.

In this study, the overall rate of reported arthritis was 23%.¹ The rate was highest for females, those aged 60-65 years of age (the oldest age group surveyed), those least educated, those permanently unable to work and in low-income families. Perhaps the most interesting finding, however, was that the rate of arthritis reported was highest for people living in the most disadvantaged neighbourhoods. Independent of age, sex, education, occupation and household income, people living in socially disadvantaged areas were 42% more likely than those living in affluent areas to self-report arthritis as a chronic health condition.¹

This study is the first to examine the association between socially disadvantaged areas and arthritis using multilevel analysis. It provides new, important information showing that one’s place of residence may be an independent risk factor for developing arthritis.

The authors hypothesise many possible explanations for this finding. Perhaps increased medical check-ups are more common in more affluent areas, enabling identification of potential health problems before onset.¹

Perhaps areas with more social capital have better access to health promotion resources.⁶ The authors acknowledge that previous studies have demonstrated higher rates of obesity, physical inactivity and more physically demanding occupations in lower socioeconomic areas.⁷ These lifestyles are less protective of arthritis. 

There are some limitations to this study, which the authors acknowledge.¹ The population sample in the HABITAT study was a convenience sample and not specifically chosen in relation to the incidence of arthritis. There was a high non-response rate (31.5%), with the highest incidence of non-responders coming from more disadvantaged neighbourhoods, on a background knowledge that studies have shown that people living in a disadvantaged area are less likely to respond to surveys. The study was also unable to capture what percentage of respondents had osteoarthritis or rheumatoid arthritis. 

However, the study does highlight very interesting new information which is relevant to all health professionals. When considering risk factors for arthritis, this study suggests we should now be giving due consideration to a person’s place of residence. It is the first study to demonstrate that arthritis incidence may be increased in areas of lower socioeconomic status, regardless of individual household income, education and occupation.¹ Further research is required to either validate or dispute these findings, and to determine if they are applicable to an Irish population.

Research is also required to determine the reasons behind the increased incidence. However, this information could potentially have important implications in Irish arthritis policy-making, health promotion and treatment. 

Conclusion

Medical and social costs associated with arthritis are high in Ireland.³ Health professionals need to concentrate on reducing modifiable risk factors through effective health promotion campaigns to decrease the arthritis rates in Ireland. This Australian study showed that people living in socially disadvantaged areas were 42% more likely than those living in affluent areas to self-report arthritis as a chronic health condition.¹

This was independent of age, sex, education, occupation and household income. It may be useful to investigate if there is indeed an increased incidence of arthritis in socially disadvantaged areas compared to affluent areas in Ireland. It may be beneficial for health professionals to increase their attention towards patients from socially disadvantaged districts for future arthritis health promotion strategies. Although the results of this study are yet to be replicated for an Irish population, they are certainly food for thought.

References

1. Brennan SL, Turrell G. Neighborhood disadvantage, individual-level socioeconomic position, and self-reported chronic arthritis: a cross-sectional multilevel study. Arthritis Care Res 2012; doi: 10.1002/acr.21590
2. Pendleton A, Arden N, Dougados M et al. EULAR recommendations for the management of knee osteoarthritis: report of a task force of the standing committee for international clinical studies including therapeutic trials (ESCISIT). Ann Rheum Dis 2000; 59: 936-944
3. Arthritis Facts. [Internet]. Available from: http://www.arthritisireland.ie/go/about_arthritis/arthritis_facts
4. Hunter N. Arthritis in Ireland – the painful truth. [Internet]. 2005. Available from: http://www.irishhealth.com/article.html?id=7666
5. Division of adult and community health, national center for chronic disease prevention and health promotion. [Internet]. 2010 Aug 1 [updated 2011 Nov 1]. Available from: http://www.cdc.gov/arthritis/basics/risk_factors.htm
6. Stafford M, Marmot M. Neighbourhood deprivation and health: does it affect us all equally? Int J Epidemiol 2003; 32(3): 357-366
7. King T, Kavanagh AM, Jolley D et al. Weight and place: a multilevel cross-sectional survey of area-level social disadvantage and overweight/obesity in Australia. Int J Obes 2006; 30(2): 281-7