A longitudinal study of joint pain in older people

I.P. Donald1 and C. Foy2

1 Elderly Care Unit and 2 Research and Development Support Unit, Gloucestershire Hospitals NHS Trust, Gloucester, UK.

Correspondence to: I. P. Donald, Elderly Care, Gloucestershire Royal NHS Trust, Great Western Road, Gloucester GL1 3NN, UK. E-mail: ecare{at}blueyonder.co.uk


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background. Joint pain is extremely common in older people, but its natural history has been little described in the UK literature.

Methods. A UK general practice population was followed for 1 yr in 1998. There were 4804 subjects aged 75 yr and over who accepted the offer of health screening. Assessments by postal questionnaire using the Elderly At Risk Rating Scale, which includes one question specifically covering joint pain.

Results. Some degree of joint pain was reported by 83%. This was related to age and female gender. The presence of pain was strongly related to mobility, energy and sadness. Over 1 yr, 18% acquired or had increased frequency of pain, while 14% had reduced frequency of pain. Resolution was associated with preserved indoor mobility, and functional recovery. There was little relationship between joint pain and adverse outcomes.

Conclusions. Joint pain is very common in older people, fluctuates in frequency over time, and is strongly linked to psychological factors as well as disability. A positive approach to active management of joint pain is justified, and will be rewarded by improved quality of life for older people.

KEY WORDS: Joint pain, Prevalence, Older people, Natural history


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Arthritis and associated joint pains are probably the most common cause for disability and handicap in older people, yet their prevalence has been little studied. It might be presumed that joint pains are an inevitable association with ageing and a permanent feature of life in old age. We are not aware of any longitudinal studies in older people in the UK which have reported specifically on joint pains.

There are very few published epidemiological studies of joint pain in the UK: a postal survey of households in Calderdale, Yorkshire was carried out in 1986 [1] but this study aimed to focus on people under the age of 75. The prevalence of chronic pain was studied in a very large population study in the Grampian region of Scotland, which included 346 subjects aged 75 and over [2], and in the North of England, including 138 subjects over 75 [3]. The largest UK study is from Glossop [4], which included more than 1100 subjects aged over 75 yr, and found 63% of women and 49% of men reporting joint pain at one site at least. In a French survey of 741 subjects [5], joint pain was found in 36% of men and 43% of women aged more than 75 yr, while a prevalence of 66% in men and women was shown in 1389 subjects aged over 75 yr in the Iowa 65+ Rural Health Study [6]. The Goteborg longitudinal study of ageing has examined joint pains in two cohorts totalling 2403 subjects, of whom 1042 were re-interviewed after 4 yr [7]. The results presented here relate to a controlled study of 4804 subjects assessed by postal questionnaire in 1998 and reassessed 1 yr later. The study recruited subjects on the basis of the Over 75 Health Check which general practitioners (GPs) in the UK are expected to offer each year to patients aged 75 or over.


    Methods
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Subjects were recruited as part of a randomized controlled trial (RCT) evaluating the benefit of targeted nurse visits (IP Donald, C Foy, C Jagger, manuscript in revision) Following an invitation letter to all practices in West Gloucestershire, 17 practices with enthusiasm and expertise in Over 75 screening were identified. Twelve of these practices were enrolled in the study. These practices represented a range of locations but with a predominance of rural towns, reflecting the population of Gloucestershire: six were in rural towns, four of the six being the sole practice for the locality; three were suburban practices, and three urban practices. All the practices have less than 5% of ethnic minorities on their lists. Townsend scores are a measure of deprivation based upon four items extracted from OPCS surveys; here Townsend scores were derived from the postal code of each patient on the practice register. The Townsend scores were all in a narrow band: five of the practices had slightly negative Townsend deprivation scores (range –1.99 to –0.16) and seven slightly positive scores (range 0.11–0.88).

For the RCT, practices were randomized by sealed envelopes to either an intervention group or a control group. Nurses within the intervention targeted their preventive visits at those subjects whose initial questionnaire indicated moderate or severe physical disability, and also at those with low self-rated health. The control nurses continued to offer health checks to all those aged 75 or over. The available options for treatment intervention were no different in the two sets of practices.

All practices had a certain amount of nursing time dedicated to preventive work with the over-75s, and this varied from 10 to 25 h per week per practice, reflecting the size of their over-75 population. All patients aged 75 yr or over on 1 May 1998 in 12 practices were identified, and sent the postal version of the Elderly At Risk Rating Scale (EARRS) [8]. This consists of 20 domains, each with five hierarchical, categorical responses, which cover activity and mobility, personal activities of daily living, mental health, and support at home. It was designed to satisfy the requirements of the Over 75 Health Check as defined by the 1990 GP contract. The score is the summation of all 20 responses and ranges from 20 to 100; quartiles for this age of population are typically around 30, 35 and 40.

The sample size was intended to be 3000 in each group, which, ignoring cluster effects, would enable the study to detect functional decline reduced from 19% to 16% or less. If the intra-class correlation was assumed to be 0.01, the study would be able to detect a functional decline of 12% with a power of 85%, assuming a response rate of 80% each year. The RCT showed no difference in overall outcomes between the groups, but a trend (P = 0.06) towards reduced rates of functional decline in the intervention practices for subjects with initial disability.

EARRS was originally designed for nurse interview, and required minor modifications as well as reprinting with larger fonts to be used as a postal questionnaire. Questionnaires were posted to 30 patients attending an elderly care day hospital, and responses were compared with a nurse interview. Weighted kappa scores ranged from 0.58 to 0.91 with a mean of 0.75, indicating good overall agreement.

A subgroup of 457 disabled subjects (EARRS score >35 at baseline) within the intervention arm of this study received postal assessments every 4 months. The whole cohort received a final postal assessment at 1 yr.

Item on joint pain
The data presented are based principally on the responses to a single item within EARRS on joint pain. Cases were identified by the response to the question: Regarding joint pains, do you (i) have no trouble at all? (ii) have only occasional pains? (iii) have pains some of the time? (iv) have pains a lot of the time? (v) have pains virtually all of the time? The case definition for this study is therefore related to those pains that older people perceived as being related to their joints, and was a subjective global assessment of their current perception of pain. Diaries were not used. No specific instruction was included within the question as to whether to include or exclude back pain. Weighted kappa for this question was 0.84 for two interviewers, 0.80 for test–retest reliability and 0.77 for agreement between self-assessment and nurse interview.

Analysis
To simplify the presentation of data, the categories of ‘No trouble’ and ‘Only occasional pain’ have been condensed to ‘No pain’; the category ‘Some of the time’ has been termed ‘Episodic’; and the categories ‘a lot of the time’ and ‘All of the time’ have been condensed to ‘Constant pain’. Functional change using the EARRS was defined as a change of 6 or more points, and has been derived from relating repeatability measures [8]. An increase of at least 6 points equates to acquiring at least two new problems in activities of daily living. Statistical analysis was carried out in SPSS release 11.5. First-stage analysis adjusting for the effect of age and gender was used to analyse in turn the relationship of each question within EARRS to the frequency of pain; the factors which showed a significant relationship were then entered into a multiple linear regression. The acquisition and resolution of pain over 1 yr was analysed by logistic regression adjusted for age and gender, with forward conditional entry of all baseline responses other than pain. In this case, the responses to questions were entered as the presence or absence of problems to enable the use of odds ratios (ORs).

Consent was obtained from GPs, but was not explicitly sought from individuals. Completion of the questionnaire by the patients was taken as implied consent to participate in the questionnaire study. Consent for the RCT was separately obtained. The study was approved by the Gloucestershire Research Ethics Committee on the understanding that the questionnaires remained the property of the general practices, and computerized data did not contain any personal identifiers, using only gender and year of birth.


    Results
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Prevalence of joint pain in older people
The response rate to the postal questionnaire was 77%, providing 4804 patients, with a mean age of 80.7 yr in 1998; the proportion of females was 58%. All respondents completed the question on joint pain, and the prevalence of joint pain is shown in Table 1. The percentage reporting any degree of pain was 83%. The prevalence of constant pain was 26%, and was higher in women ({chi}2 = 80, P<0.001) and in the over-85s ({chi}2 = 21, P<0.001): 20% of men under 85 and 24% of men over 85; 28 and 34% of women respectively. Frequency of pain increased across 5-yr age bands in women ({chi}2 for trend 5.8 with 1 degree of freedom, P<0.001), and in men ({chi}2 for trend 17.0, P = 0.016).


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TABLE 1. Number of subjects (%) with each frequency of joint pain by age group in 1998

 
Relationships between joint pain and other factors
The frequency of joint pain was significantly associated with 17 of the other 19 questions within EARRS, after adjusting for age and gender using partial correlation coefficients. This confirms that joint pain was associated with disability and dependency across a wide range of problems. One in five older people with constant pain was housebound, compared with only 6% of those without pain. Pain was also associated with a threefold increased likelihood of dependency for activities of daily living. Constant joint pain was associated with a fourfold increase in recurrent falling. Seventy-six per cent of those with constant pain reported limited energy, compared with only 26% of those free of pain.

Of course, much of this relationship is confounded by the increased prevalence of disability in older women, who also were more likely to have pain. In multiple logistic regression, adjusting for age and gender, comparison was made between those with no pain or episodic pain, and between those with no pain or constant pain. The strongest factors were need for foot care, self-rated energy, sadness, and problems with housing, while indoor mobility, falling, number of drugs and carer frequency were also consistently related (Table 2).


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TABLE 2. Multiple logistic regression of associations between pain and baseline disability factors

 
Fluctuations in joint pain
Replies to a second questionnaire 1 yr later were received from 3850 subjects (80% of initial responders): 240 (5%) died, 65 (1.4%) moved into care, 554 (11.5%) did not respond but were still alive and living in the locality, and 95 (2%) had moved away (Fig. 1). Although joint destruction from arthritis will be permanent once developed, the severity and frequency of joint pain may be intermittent. Fourteen per cent of subjects reported less joint pain, and 18% reported more pain at interview 1 yr later. Constant pain was present both years in 18%, pain was absent both years in 38%, and 12% had episodic pain both years. There were no differences in these percentage changes between the intervention and control practices.



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FIG. 1. Flow diagram of patients in the study.

 
In the subgroup of 457 subjects with at least moderate baseline disability assessed every 4 months, 68% of subjects reported the same frequency of pain, 17% reported improved pain, and 15% more frequent pain after 4 months. These are similar figures to the 1-yr transition probabilities above. Of these subjects, 425 returned each of the four questionnaires over the year. The distribution of pain at each assessment is shown in Table 3, and was broadly constant through the year. Interestingly, 65% of those with no pain initially continued free of pain at each assessment; corresponding figures for episodic pain and constant pain were 33 and 9%. Constant pain was experienced at least once in the four assessments by 35% of this subgroup.


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TABLE 3. Distribution of pain frequency in 425 subjects assessed every 4 months for 1 yr (percentages)

 
Acquisition of joint pain
Of the 2303 subjects with no joint pain initially, 1917 replied to the questionnaire 1 yr later. Of these, 76% still had no pain, while 19% had acquired episodic pain, and 5% had constant pain. Logistic regression analysis has been used to see which factors influenced the probability of acquisition of joint pain, whether episodic or constant. Rates of acquisition were similar in men and women, and were unrelated to age. Acquisition was more frequent in those with higher baseline disability: baseline EARRS was 29.5 for those who did not acquire pain and 33.0 for those who did so. Independent factors related to acquiring pain were initial incontinence (OR = 2.7, 95% CI 1.5–4.8), sadness (OR = 1.7, 95% CI 1.1–2.8) and dependency for washing (OR = 1.9, 95% CI 1.3–2.6).

Resolution of joint pain
Of 1268 subjects with episodic pain and 1273 subjects with constant pain, 962 and 971 respectively were assessed 1 yr later. Of those with episodic pain, 26% lost their pain and 24.5% developed constant pain. Of those with constant pain initially, 72% still described constant pain and 21% episodic pain; 7% had lost their pain. Logistic regression analysis was used to see which factors influenced the probability of improvement in joint pain, and this was unrelated to age or baseline disability, but was more common in men (OR = 1.3, 95% CI 1.0–1.3). The only other independent predictor found was good initial indoor mobility (OR = 1.4, 95% CI 1.1–1.8), which predicted greater likelihood of resolution of pain. Changes in energy over the year showed a significant drop in those who acquired pain by comparison with those who remained without pain (Mann–Whitney U-test, P<0.0001); similarly, there was a significant increase in energy in those who lost their pain by comparison with those who remained with their pain (Mann–Whitney, P<0.0001).

Relationship between joint pains and adverse outcomes
Functional decline (an increase of 6 or more points on EARRS) over 1 yr was seen in 18% of people over 75 yr, and functional gain in 7%. There was no relationship between initial joint pain and the probability of either functional decline or recovery. However, there was a strong relation between functional decline and acquiring joint pain: 31% of those who acquired joint pain also experienced functional decline over the year, compared with 13% decline in those who did not acquire new joint pain ({chi}2 = 76, P = 0.001). There was a similar strong relationship between functional recovery (an improvement of 6 points) and resolution of joint pain: 17% of those who lost their pain also had functional gain, compared with 6% of those whose pain had persisted ({chi}2 = 32, P = 0.001).

Crude 1 yr mortality rates were 5.4, 10.1 and 9.9% for no pain, episodic pain and constant pain respectively in men; the equivalent figures for women were 3.4, 5.4 and 4.3%. Using logistic regression, entering age and baseline mobility, joint pain was no longer related to mortality. There was no relationship between admission rates to care homes with the presence of joint pain.


    Discussion
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Joint pain was experienced by the majority of people over 75 yr. The definition of self-perceived joint pain was inevitably subjective, and does not relate to any specific diagnosis or pathology. The importance of studying joint pain has been emphasized recently in the context of knee pain [9], as this forms the first step in health-care needs assessment and the development of management strategies. Subjects with joint pain are far more numerous than those with significant radiological abnormality. For instance, in one American study of a general population of 6880 people [10], arthritis on X-ray was found in 3.7%, of whom half suffered pain; however, knee pain was reported by 15% of the population, and only 15% of these had an abnormal X-ray indicating arthritis. This demonstrates the difficulty of matching pain and a radiological diagnosis of arthritis in older people. Nevertheless, joint pain is easily understood by the public, and provided consistent responses in test–retest interviews. A weakness of this study is the lack of clarity as to whether subjects included back pain in their response to the question on joint pain. However, in examining changes within the same individuals over 1 yr, it can be assumed that individuals will have used the same definition each year.

Comparison with previous studies
The prevalence of joint pain in older people in this study was 83%. These figures compare with a prevalence of 62% for chronic pain in the same age group in Scotland [2], 71% for any complaint of pain in over-75s in France [5], 66% for joint pain in the over-75s in Iowa [6], and only 43% in Sweden [7]. Constant limb joint pain in those studies was 28% [2] and 19% [6] respectively, which compares with 26% in this study.

Joint pain has been shown to be more prevalent in women than men, as found in other studies [1–7]. The increasing prevalence of joint pain with age has been shown previously up to the age of 75 [1–3], while the Glossop study [4], the French study [5] and the Swedish study [7] showed no further increase of pain over the age of 75. In Iowa, there was a small drop in the prevalence of joint pain in the over-85s [6]. In this study, there was a linear increase in pain with age, which was more marked for women. Nevertheless, it is perhaps reassuring that pain, and certainly constant pain, is by no means ubiquitous amongst older people, as at least 20% were free of pain.

The impact of the joint pains can be gauged by the associations of pain with poor mobility, activities of daily living dependency, and falling. Three quarters of those with constant pain reported limited energy, and multiple regression showed an independent relation between constant joint pain and both low energy and sadness: chronic pain is strongly associated with psychological distress and fatigue [11, 12]. Resolution of pain was associated with improved energy and no doubt quality of life.

Relapsing and remitting nature
The relapsing and remitting nature of joint pain was demonstrated within the longitudinal nature of these studies. This clearly stands in distinction from radiographic changes, which are more likely to deteriorate steadily. Almost as many subjects experienced a reduction in their pain over a time period as experienced an increase in pain, but remission was more common in men than women. The Swedish study, examining changes over 4 yr, found acquisition of pain in 23% of women and 17% of men, with resolution in 40% of women and 59% of men. However, over 4 yr, survival effects will provide the major explanation of the pain outcomes observed. This understanding of the natural history of joint pain is important for general practitioners when making decisions about duration of drug treatment and referral for surgery. Sadness and dressing dependency were found to be predictors of acquiring joint pain; these may be early markers of functional decline which frequently accompanied new joint pain. Preserved indoor mobility at baseline predicted subsequent resolution of pain, and resolution was associated with greater likelihood of functional gain.

Joint pain and adverse outcomes
There was a weak relationship between joint pain and mortality, and once adjustment was made for disability this was lost. There was no relationship between joint pain and admission into care. A study from Rotherham [13] found the same result, and emphasized that hospital admission rates and mortality rates do not necessarily serve as an indicator of the level of morbidity caused by a condition: they found a relationship for respiratory disease with hospital admission and mortality, but not for arthritis. Disability, measured by many other elements within the EARRS questionnaire, is a far stronger predictor of adverse outcomes than joint pain [14]. Criteria for entry into care are probably driven more by functional disability than well-being influenced by pain.

Limitations and generalizability of findings
It was not possible to verify the accuracy of the practice registers, and therefore some patients were likely to have moved, thus reducing the apparent response rates. The major limitation of this study was as a consequence of collecting only a single question regarding joint pain frequency—no information was gathered on the severity of pain, the duration of pain or the site of pain, nor was a diary method used. It would be helpful to know if the correlations found here in relation to the frequency of pain held true also in relation to the severity of pain. Joint pains from different sites are likely to have a differential impact on disability and adverse outcomes.

The Townsend scores for the practices showed deprivation levels representative of England as a whole. Non-responders to the original questionnaire were slightly older (82.9 vs 80.6 yr, P = 0.001) and included 18.7% of men and 18.9% of women. Those who were alive but defaulted at 1 yr were of similar age but had been more disabled at baseline (EARRS mean score 38.7 for defaulters vs 34.8 for responders), and had higher prevalence of baseline constant pain (30 vs 25%). As acquisition of pain was related to higher baseline disability, the defaulters may have diminished the true figure for pain acquisition.

The association of constant pain with disability, falling and low energy, and the high remission rate of constant pain, should encourage prompt active management of joint pain, with the expectation of improving symptoms and quality of life for older people.


    Acknowledgments
 
We are grateful to the Edith Mackay bequest and the Gloucestershire Arthritis Trust for kindly and jointly supporting the 1998 study—the randomized trial of nurse intervention in general practice. Without their support, this study would not have been possible. For their support and cooperation, we are also indebted to all the general practitioners, and especially the nurses, within the practices which kindly participated in these two studies. We are grateful to Dr Peter Croft, Department of General Practice, Keele University, for his advice in preparing the manuscript, and to Dr Jake Abbas, Public Health, Cheltenham and Tewkesbury Primary Care Trust, for performing the Townsend analyses.

The authors have declared no conflicts of interest.


    References
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

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Submitted 7 May 2003; revised version accepted 4 June 2004.