Previous research established links between pain and cognitive function on one hand and pain and anxiety on the other, and there is some evidence linking osteoarthritis to lower educational attainment. However, the inter-play of these factors and the role of key social factors (social deprivation) at the early disease stages are not understood. Using data from waves 4, 5, 6 and 7 of the Survey of Health, Ageing and Retirement in Europe (SHARE) (n = 1,240), we tested how social deprivation, education and anxiety, before diagnosis, affects the relationship between cognitive function, pain and independence (activities of daily living) in a subsample of respondents reporting a diagnosis of osteoarthritis at wave 6, with cross-lagged panel models. We show that social deprivation, before osteoarthritis diagnosis, predicts functional impairment in daily living after diagnosis, with this effect partly mediated by impaired cognitive function, and that education before diagnosis is protective against impairments in daily living after diagnosis via better cognitive function and lower anxiety at wave 5. Therefore, improving cognitive function and managing anxiety may mitigate the negative impact of social deprivation and low educational attainment on independent living and help to promote independence in patients with osteoarthritis.
Research Article
Pathways To Pain And Disability: The Impact of Early Social Deprivation And Educational Attainment In Newly Diagnosed Osteoarthritis Patients
https://doi.org/10.21203/rs.3.rs-247989/v2
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The relationship between cognitive function and pain is well established, with good cognitive function protective against pain and pain associated with cognitive impairment (1–4). Furthermore, poorer educational attainment has been shown to genetically correlate with osteoarthritis (5), and links between anxiety, heightened pain and impaired activities of daily living in osteoarthritis have been identified (6–10). However, the role of social deprivation, defined as social isolation and lack of social support (11), and the early inter-play of social, affective and cognitive factors, before a diagnosis of osteoarthritis, on subsequent patient outcomes, such as pain, independence and cognitive decline, is not understood. As affective and cognitive factors are influenced by the experience of pain (1–4), it is necessary to assess these factors prior to disease associated with pain (osteoarthritis) in order to show their unconfounded effects on subsequent pain and impairments. This would allow us to identify factors that could be the target of early interventions to reduce the costly disability caused by osteoarthritis (12). We analysed data over four consecutive waves from the Survey of Health, Ageing and Retirement in Europe (SHARE), a large longitudinal survey covering 28 European countries (13), which allowed us to follow the trajectory and development of osteoarthritis over time (i.e. before, during and after diagnosis). We assessed the role of social deprivation, anxiety and cognitive function before a diagnosis of osteoarthritis on independence, pain and cognitive function after the onset of osteoarthritis in a carefully selected sample of newly diagnosed osteoarthritis patients.
Social deprivation impacts pain (14–17), as well as cognitive decline (18, 19). However, the mechanisms underlying the link between social deprivation and impairments in activities of daily living are not well understood. It has been shown, that social engagement inhibits atrophy in cognitive abilities and promotes independence in old age (20–23), whereas lacking social support makes us more susceptible to disease (24, 25). Here, we tested for the first time how social deprivation, assessed before osteoarthritis diagnosis, impacts cognitive function, pain and independence in daily living following diagnosis. We aimed to disentangle the links between social deprivation, cognitive function, educational attainment and anxiety, before diagnosis, and how these impact pain and independence following diagnosis.
Study population
Data were taken from waves 4 (2011/2012) (26, 27), 5 (2013) (28, 29), 6 (2015) (30, 31) and 7 (2019) (32, 33) of the SHARE study, a multidisciplinary, cross-national, and longitudinal research project focusing on community dwelling adults aged 50 or older (13). Detailed information about the entire SHARE project is available at www.share-project.org. SHARE respondents were included in our subsample if: (a) they had participated in wave 4 and did not report a diagnosis of dementia, Alzheimer’s, senility or Parkinson’s at waves 4 and 5 (i.e., before the diagnosis of osteoarthritis, see next inclusion criterion); (b) they reported a diagnosis of osteoarthritis at wave 6; (d) they did not report a diagnosis of osteoarthritis at wave 5; (e) they participated in wave 7; and (f) continued to report a diagnosis of osteoarthritis at wave 7 (Fig. 1). Of the 1,240 participants included in our analysis, twelve had missing data on all measurements of pain and cognitive function, which were accounted for using a full information maximum likelihood (FIML) estimation. Osteoarthritis diagnosis was assessed at all waves with the following question: “Has a doctor ever told you that you had/Do you currently have: Osteoarthritis? (With this we mean that a doctor has told you that you have this condition, and that you are either currently being treated for or bothered by this condition.)”(29). At the time of diagnosis, 509 (41.05%), 263 (21.21%), 443 (35.73%), 416 (33.55%), 59 (4.76%) participants reported to have back pain, hip pain, knee pain, pain in other joints, pain all over, respectively, whereas for 286 (23.06%) participants we miss information about which joints were painful.
Ethics approval and consent to participate
The SHARE data collection procedures are subject to continuous ethics review by responsible ethics committees (University of Mannheim and Max Planck Society, Germany) as well as national ethics committees in participating countries. The reviews refer to all aspects of the project, from study design to informed consent. The reviews confirm the project agrees with international ethical standards, such as the Respect Code of Practice for Socio-Economic Research and the 'Declaration of Helsinki'.
For the purpose of the present study, appropriate permission was obtained for use of the SHARE data after successful application. The applicant is required to agree that use of the SHARE data will be purely for scientific purposes, provide appropriate information regarding their scientific alignment and agree to the SHARE Conditions of Use [http://www.share-project.org/data-access/share-conditions-of-use.html?L=]. Following successful application, the data can be accessed for free upon registration. The secondary analysis performed here required no ethical approval from an ethics committee or an institutional review board.
Variables
Cognitive function
Cognitive function was assessed at all waves and was based on multiple items: (1) immediate recall (participants were presented a list of 10 words and asked to repeat the words immediately; range = 0‐10), (2) delayed recall (participants were asked for the list of 10 words after a delay; range = 0‐10), (3) subtraction (participants were asked to mentally solve a subtraction task; range = 0‐5), and (4) verbal fluency (participants were asked to produce as many animal names as possible within a given period of time; range = 0-100). A joint scale was created based on all items with a total score range of 0 to 125 (Cronbach’s alpha = 0.80, for wave 5 and Cronbach’s alpha = 0.76, for wave 6). The higher the score, the higher the participant’s cognitive function (34). These cognitive measures are validated and are widely used in many large longitudinal surveys (34, 35). Our calculated Cronbach’s alphas demonstrated good internal consistency reliability of the cognition scale. We decided not to use a standardised score of cognitive function due to the risks associated with their use in the analysis of longitudinal data (36, 37).
Pain
A pain score was constructed from two questions asked at all waves of the survey. Participants were asked whether they had been troubled by pain (yes/no). Those who replied positively were then asked to rate how bad their pain was most of the time (either mild, moderate or severe). The two variables were added to create a single score ranging from 1 (not troubled by pain) to 4 (troubled by severe pain), representing whether respondents were troubled by pain and how severe it was. This verbal rating scale used in the SHARE and other large longitudinal studies has been used widely in the pain literature (38). Comparative and clinical trial studies (39-42) have assessed the validity and reliability of this pain measure. Measurements using this verbal rating scale (0-4) are highly correlated with measurements using visual analogue or a numeric rating scale, and has similar precision for discriminating between treatments in OA patients (41, 42).
Anxiety
In SHARE wave 5, five items were used to measure severity of anxiety that were taken from the Beck Anxiety Inventory (43). The respondents were asked about anxiety symptoms (“I had fear of the worst happening”, “I was nervous”, and “I had a fear of dying”, “I felt my hands trembling”, “I felt faint”) they experienced in the last 7 days and answer on a four point Likert scale (“never”, “hardly ever”, “some of the time”, “most of the time”). We created a single anxiety scale by adding the scores of all five items to obtain an overall score, with higher scores indicating higher anxiety (Cronbach’s alpha = 0.69). These items have extensively been used in large longitudinal studies like the Health and Retirement Study and have been shown to distinguish symptoms of anxiety from depression and to be valid for use in older populations (44). Our calculated Cronbach’s alpha of .69 demonstrated good internal consistency reliability of the anxiety scale.
Social deprivation index
A social deprivation index was provided in wave 5 of SHARE that was generated and validated by Michał et al. for the purpose of the SHARE study (45). Briefly, this index was constructed using a battery of 15 questions related to participation in everyday life, social activities and the quality of the neighbourhood following Chakravarty and D'Ambrosio (46) and Levitas, Pantazis (11). In order to combine different social deprivation items into a single index, Michał et al. computed the weight of each item based on a regression of the chosen items on the reported values of life satisfaction (45). The most important elements of the index, i.e. those with the highest weight are: feeling left out of things, not feeling part of the neighbourhood, having no helpful people in the local area and waiting too long to see a doctor (45).
Instrumental activities of daily living (IADL)
A modified version of IADL (47) was used in SHARE (48). IADL included seven activities in wave 5: “using a map to get around in a strange place”, “preparing a hot meal”, “shopping for groceries”, “making telephone calls”, “taking medications”, “doing work around the house or garden” and “managing money” with a total score ranging from 0 to 7. Two more items were added in waves 6 and 7: “leaving the house independently and accessing transportation services”, and “doing personal laundry”, resulting in nine items in total (score: 0-9). A higher index score indicates more difficulty with these activities and lower mobility of the respondent (Cronbach’s alpha = 0.71, 0.80 and 0.86, for waves 5, 6 and 7, respectively). Our calculated Cronbach’s alphas demonstrated good internal consistency reliability of the anxiety scale.
Additional variables
Other variables included age (>50 y.o.), gender, education measured with the International Standard Classification of Education (ISCED‐97) (49), body mass index (BMI), smoking status (Currently smoking, Ex-smoker, Never smoked, and No response), alcohol consumption (How many drinks in 3 months), physical inactivity (Never moderate or vigorous activity and Other), number of chronic diseases (0-9), and marital status (Married and living together, Divorced, Widowed, and Other).
Statistical analysis
Modelling was performed using R version 4.0.1. For path analysis the ‘lavaan’ package was used (50). The missing mechanism of the SHARE data is assumed to be missing at random and the level of dropout in this subsample is small (17.1%), thus, missing data were handled using FIML. We conducted sensitivity analyses using multiple imputations (m = 40). No significant differences between the two methods for handling missing data were found (see Supplementary File 1).
Crossed-lagged path analysis was run using the pain and cognitive function measurements at waves 5 and 6 and IADL at waves 5, 6 and 7. The path model was constructed such that pain levels, cognitive function, and IADL each predicted each at the following wave. The path model was adjusted for age, sex, education level, number of chronic diseases, BMI and alcohol consumption at baseline. Confounding variables were chosen due to their clinical relevance to chronic pain and cognitive function based on findings from other studies (2). Correlational analysis between the study variables was done to determine which variables were entered in the final model (See Supplementary Table 7, Supplementary File 1 for correlational analyses).
Model fit was assessed using the Comparative Fit Index (CFI), the Tucker Lewis Index (TLI), the Root Mean Square Error of Approximation (RMSEA) and the Standardised Root Mean Square Residual (SRMR). To determine acceptable fit we used the cut-off criteria proposed by (51), who recommended that an RMSEA lower than .06 and CFI and TLI greater than .95.
Descriptives
Descriptive statistics for the sample are reported in Table 1. All fit indices suggested the model fits these data well (RMSEA = 0.038, 95% CI 0.028-0.048, SRMR = 0.021, CFI = 0.987, TLI = 0.960) (See Supplementary Table 1, Supplementary File 1).
Table 1. Descriptive statistics (n = 1,240)
|
Characteristics |
W4 |
W5 |
W6 |
W7 |
|
Age |
66.65 (9.17) |
68.65 (9.17) |
70.65 (9.17) |
72.65 (9.17) |
|
BMI |
27.69 (5.10) |
27.34 (6.17) |
27.04 (6.94) |
26.92 (7.03) |
|
No. of chronic diseases |
2.05 (1.54) |
1.88 (1.50) |
3.03 (1.63) |
3.12 (1.69) |
|
Social deprivation index1 |
- |
0.18 (0.14) |
- |
- |
|
Cognition total score |
34.46 (10.56) |
34.86 (11.17) |
35.05 (10.72) |
* |
|
Level of pain |
** |
2.27 (1.11) |
2.60 (1.05) |
* |
|
Anxiety1 |
- |
7.87 (2.82) |
- |
- |
|
IADL |
0.27 (0.74) |
0.32 (0.82) |
0.58 (1.32) |
0.76 (1.63) |
|
Female Gender, n (%) |
72.25 |
72.26 |
72.26 |
72.26 |
|
Education, n (%): |
|
|
|
|
|
Low – ISCED code 0,1 and 2 |
41.00 |
40.24 |
40.16 |
40.08 |
|
Medium – ISCED code 3 and 4 |
37.75 |
37.63 |
37.71 |
37.50 |
|
High – ISCED code 5 and 6 |
21.15 |
21.55 |
21.55 |
21.62 |
|
Other |
0.60 |
0.57 |
0.57 |
0.56 |
|
Marital status, n (%) |
|
|
|
|
|
Married and living together |
64.25 |
50.00 |
45.07 |
* |
|
Divorced or widowed |
28.50 |
45.00 |
49.29 |
* |
|
Other |
7.18 |
5.00 |
11.27 |
* |
|
Physical activity, n (%) |
|
|
|
|
|
Other |
90.28 |
88.47 |
87.02 |
* |
|
Never vigorous or moderate |
9.72 |
11.45 |
12.98 |
|
|
Alcohol consumption, n (%) |
|
|
|
|
|
Not at all in the last 3 months |
74.23 |
71.01 |
82.18 |
* |
|
Less than once a month |
14.30 |
15.02 |
7.98 |
* |
|
Once or twice a month |
6.85 |
7.80 |
5.00 |
* |
|
More than once or twice a month |
4.59 |
3.60 |
4.84 |
* |
|
Smoking status, n (%) |
|
|
|
|
|
Currently smoking |
15.61 |
12.93 |
* |
* |
|
Never smoked daily |
62.12 |
72.00 |
* |
* |
|
No, I have stopped |
22.27 |
15.07 |
* |
* |
|
Affective/emotional disorder2, n (%) |
- |
6.13 |
8.31 |
8.23 |
|
At risk of severe deprivation1, n (%) |
- |
14.20 |
- |
- |
*It is not reported here due to more than 50 % missing values in this variable.
** Pain intensity was not assessed in wave 4 of the SHARE. However, 75.56% participants reported being bothered by pain in back, knees, hips or other joint at wave 4.
1It was only measured at wave 5 of the SHARE
2It was not measured at wave 4 of the SHARE
Direct Effects
The significant relationships are highlighted in the path model in Figure 2 (for all outcomes of our analysis, See Supplementary Table 2, Supplementary File 1). The main finding was that social deprivation before diagnosis predicted higher pain levels and impaired cognitive function after diagnosis (wave 6). Increased pain and anxiety before diagnosis predicted more impairments in activities of daily living after diagnosis, whereas better cognitive function before diagnosis predicted less functional impairments in daily living after diagnosis. Better cognitive function at wave 6 predicted less impairments in activities of daily living at wave 7, whereas wave 5 anxiety predicted more limitations in activities of daily living at wave 7.
Indirect Effects
Looking at the indirect paths (Table 2), social deprivation, before diagnosis, predicted impairments in activities of daily living, following diagnosis, through its negative effect on cognition (wave 5 social deprivation -> wave 6 cognition -> wave 7 IADL), suggesting that one mechanism underlying the link between social deprivation and impairments in daily living is via cognitive ability. Furthermore, higher educational attainment predicted better cognition, before and after diagnosis (wave 4 education -> wave 5 cognition -> wave 6 cognition). Looking at the total indirect effects, social deprivation before diagnosis predicted impairments in daily living following diagnosis via poor cognitive function and pain at the time of diagnosis. Higher educational attainment, prior to diagnosis, was protective against impairments in daily living after diagnosis via better cognitive function and reduced pain as well as via better cognitive function and lower anxiety at the wave before diagnosis (wave 5).
Table 2. Indirect paths predicting pain at wave 6 and IADL at waves 6 and 7 and their total indirect effects
W, wave; A, anxiety; E, education; P, pain; CF, cognitive function; SD, social deprivation; IADL, independent activities of daily living. * = p < .05, ** = p < .01, *** = p < .001. n=1,240
We show, in a group of newly diagnosed osteoarthritis patients, that social deprivation before diagnosis predicted poorer cognitive function and higher pain levels after diagnosis. We also identified a link between social deprivation, prior to diagnosis, and more impairments in daily living following diagnosis that was mediated by impaired cognitive function at the time of diagnosis, suggesting cognitive function is a potential mechanism underlying the deprivation-functional impairment relationship. We demonstrated that education, before diagnosis, was protective against impairments in daily living following diagnosis via better cognitive function and lower anxiety, as well as via better cognitive function and reduced pain at the wave before diagnosis.
To our knowledge, no previous study has assessed the interplay of social, cognitive and affective factors before diagnosis of osteoarthritis and its impact on functional outcomes and pain severity following diagnosis. Previous longitudinal studies on the relationship between osteoarthritis pain, activities of daily living, deprivation and anxiety mostly included participants with longstanding osteoarthritis, making it hard to generalise their findings to those presenting with early disease (14, 52-55). For example, Hawker et al. (2011) constructed a path model to test the interrelationships between pain, depression, fatigue and disability over time, in participants with already established osteoarthritis (54). Harris et al. (2013) explored the impact of psychosocial risk factors (mainly perceived stress) on onset of osteoarthritis, but neither did they test the impact of these factors on functional outcome over time nor the pathways linking psychological, cognitive and social factors, and they used a women-only cohort (56). While many aspects of social context can be difficult or impossible to change, understanding the pathways linking such aspects to health outcomes at the early disease stages and including dimensions of psychological and cognitive influences not only provides a more transparent view of the relationship between social determinants and health outcomes, but also allows us to identify areas for health interventions.
The link between higher social deprivation and impaired activities of daily living and its mediation by lower cognitive function found in this study may be explained by the cognitive reserve theory. This theory suggests that continued stimulation of cognitive abilities, due to social engagement inhibits atrophy in these abilities and promotes independence in old age and is supported by previous research in humans (20-23). At the same time, both higher pain levels and impaired cognitive function might further reduce social participation and increase loneliness in seniors (57, 58), creating a vicious cycle.
It has been previously shown that low educational attainment is associated with higher pain levels and more functional disability (59) and there is a very strong relationship between risk of osteoarthritis and years of education seen in very large genetic studies (5, 60). Furthermore, education is an important determinant of cognitive function in old age (61). However, the pathways linking these factors in osteoarthritis are unknown. We found for the first time that education was protective against impairments in activities of daily living via both improved cognitive function and lower anxiety, as well as improved cognitive function and reduced pain levels. Bidirectional links between cognitive function and affect, as well as cognitive function and pain have been demonstrated previously (4, 62). However, we showed that these associations were influenced by previous educational attainment and that their interactions before diagnosis predicted activities vital to independence and self-care after diagnosis. Therefore, managing anxiety and potential problems with cognitive functioning early in the disease course has apparent clinical benefit in terms of independent living. Cognitive-based interventions, involving the education about pain processing and false beliefs about movement can result in substantial improvements in disability and performance (63-67), and should be considered as part of the arsenal of treatment options.
It is important to acknowledge the limitations of this study. The observed impairments in activities of daily living might be due to comorbid conditions, rather than osteoarthritis. However, we controlled for number of chronic conditions in our analyses and adjusted for previous IADL at each wave. Same-source bias can arise from use of perception-based measures (social deprivation index). However, perceived measures usually serve as good proxies of actual measures, as they are often highly correlated (68). As we did not have information about osteoarthritis severity, despite controlling on disease duration, respondents may have had different levels of osteoarthritis pathology. Although we used self-reported OA diagnosis, March and colleagues (69) have found that self-reported physician diagnosed general arthritis has good congruency with clinically derived diagnoses.
We show that social deprivation, before osteoarthritis diagnosis, predicts functional impairment in daily living, after diagnosis with this effect mediated by impaired cognitive function. We also show that, education before diagnosis was protective against impairments in daily living after diagnosis via better cognitive function and lower anxiety before diagnosis. Therefore, improving cognitive function and managing anxiety may mitigate the negative impact of social deprivation and low educational attainment on independent living and may help to promote independence in patients with osteoarthritis.
Acknowledgements
The SHARE data collection has been funded by the European Commission through FP5 (QLK6-CT-2001-00360), FP6 (SHARE-I3: RII-CT-2006-062193, COMPARE: CIT5-CT-2005-028857, SHARELIFE: CIT4-CT-2006-028812), FP7 (SHARE-PREP: GA N°211909, SHARE-LEAP: GA N°227822, SHARE M4: GA N°261982, DASISH: GA N°283646) and Horizon 2020 (SHARE-DEV3: GA N°676536, SHARE-COHESION: GA N°870628, SERISS: GA N°654221, SSHOC: GA N°823782) and by DG Employment, Social Affairs & Inclusion. Additional funding from the German Ministry of Education and Research, the Max Planck Society for the Advancement of Science, the U.S. National Institute on Aging (U01_AG09740-13S2, P01_AG005842, P01_AG08291, P30_AG12815, R21_AG025169, Y1-AG-4553-01, IAG_BSR06-11, OGHA_04-064, HHSN271201300071C) and from various national funding sources is gratefully acknowledged(see www.share-project.org).
Authors' contributions
AK is the primary author and analysed the data. AMV is the main supervisor. EF and TB are secondary supervisors. AMV and EF provided guidance throughout all stages of data analysis. All authors were major contributors in writing the manuscript.
Competing interests
The authors declare that they have no competing interests.
Availability of data and materials
This paper uses data from SHARE Waves 4, 5, 6 and 7 (DOIs: 10.6103/SHARE.w4.710, 10.6103/SHARE.w5.710, 10.6103/SHARE.w6.710, 10.6103/SHARE.w7.710), see Börsch-Supan, Brandt (13) for methodological details.
Supplementary Material
Supplementary File 1 of Pathways to pain and disability: the impact of early social deprivation and educational attainment in newly diagnosed osteoarthritis patients
Funding
This work was part of a PhD project funded the National Institute of Health Research via the NIHR Nottingham Biomedical Research Centre.
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No competing interests reported.