Introduction
Axial Spondyloarthritis (AxSpA) is a chronic inflammatory rheumatic disease affecting primarily the axial skeleton and sacroiliac joints. AxSpA is a painful and potentially disabling condition, typically diagnosed in early adulthood and its usual characteristics are pain, stiffness due to inflammation and impaired physical function [
1]. Non-specific low back pain is the most common spinal disorder and is defined as low back pain not related to a known specific pathology such as a tumour, infection, osteoporosis, fracture or inflammatory disorder. Low back pain is defined as chronic when the pain persists for more than 3 months and it represents between 11–12 % of all low back pain cases [
2]. Chronic low back pain also leads to pain and impaired physical function. These axial diseases have very different mechanisms (inflammatory versus mechanical) but both may have a severe impact on patients’ health related quality of life (HRQoL) in terms of physical, mental and social well-being though these have not been directly compared [
3‐
13]. There are differences in treatment options between these diseases: on top of non-inflammatory anti-steroidal drugs and physiotherapy, biologic treatments such as anti-tumor necrosis factors have been proven to be successful in reducing AxSpA symptoms and in improving HRQoL [
14], whereas for low back pain, analgesics and active physiotherapy are recommended.
The dispositional and global expectations individuals hold about success or failure are described by the constructs of optimism and pessimism. Dispositional optimism is defined as a stable, trait-like personality characteristic consisting of a general positive mood or attitude about the future with a tendency to expect favorable outcomes in life situations [
15]. In opposition to dispositional optimism, dispositional pessimism is the tendency to generally expect negative outcomes in the future [
15].
In different medical settings, optimistic people have been shown to have higher QoL compared to people with low optimism levels or pessimistic people [
15‐
17]. This has been investigated in particular in people with cancer, epilepsy, haemodialysis and in patients having undergone aortic-coronary bypass [
18‐
21]. In chronic rheumatic diseases, the few studies available also indicate optimism seems positively correlated to HRQoL [
22‐
24]. However, none of these studies was focused on axial diseases.
Exploring the relationship between optimism and HRQoL in AxSpA and chronic low back pain could have interesting practical implications. Indeed, as research has linked optimism to lower pain sensitivity and better adjustment to chronic pain [
25], it could provide important insights for clinicians regarding treatment decisions in particular in AxSpA where pharmacological treatment with biologic agents is decided mainly based on the patients’ subjective perception of their own disease [
26]. Moreover, low back pain is a complex multifactorial process influenced by somatic, psychological and environmental factors, and falls within the biopsychosocial model of disability and health [
27,
28]. Therefore, investigating levels of optimism among chronic low back pain patients can bring insights for targeting treatment such as coping enhancement techniques. Given the differences between AxSpA and low back pain, in terms of physiopathology, prognosis and treatment options, it could be expected that optimism levels might be different, and that the links between optimism and HRQoL might be different [
25].
Thus, the objectives of the present study were to explore the levels of HRQoL and optimism in AxSpA and low back pain, and the relationship between optimism and HRQoL in these two populations.
Discussion
This study shows AxSpA and low back pain patients had a decreased HRQoL, interestingly very similar in both diseases. Levels of optimism were lower than in the general population [
38] and were similar in both diseases, in the moderate range. Furthermore, there was a positive relation between optimism and mental HRQoL, but not physical HRQoL.
The present study has strengths and limitations. The issues for external validity include that the sample size was relatively small and all patients came from Paris, France; however representativity was increased by recruitment from both tertiary care and private practices and the patient characteristics are in keeping with usual data for these populations. Furthermore optimism levels have been shown to be consistent across countries [
40]. Sample sizes were different for both diseases and rather low for low back pain; this is due to the sampling method (convenience sample); thus low back pain results should be interpreted with caution. Moreover, there is a lack of data on optimism levels in the general population, and on cutoff values to interpret the LOT-R even though the LOT-R is a widely used questionnaire to assess optimism [
18‐
21,
32]. Pessimism was not assessed in this study.
In this study, AxSpA patients as well as low back pain patients suffered from poor HRQoL in terms of physical and mental well-being. Although there was no control group in this study, the use of SF12 (for which the results are calibrated in the general population) allows an assessment of HRQoL compared to the general population [
41].
These findings are in line with previous studies using the longer version of the SF-12, the SF-36 [
3‐
12,
42]. In 2 Spanish studies using the SF12, HRQoL results differed from the present findings; in AxSpA, patients had lower PCS and higher MCS [
43] and in low back pain, patients had lower PCS and MCS [
44]. The differences observed may be due to sampling differences. Indeed, regarding low back pain patients, there was no indication about disease duration and low back pain was self-assessed. This could explain why these patients suffer from a poorer HRQoL. Regarding AxSpA patients, they reported higher disease activity and lower functionality, which could explain the lower scores on the physical component of the SF-12.
The present study indicated HRQoL was similar in both diseases. This is an interesting finding, given the different physiopathological nature of these diseases. It indicates the physical impact of these diseases may be close, perhaps due to similar functional limitations because of the spinal involvement. Regarding mental health, we anticipated that low back pain patients would have a lower mental HRQoL than AxSpA patients due to the lack of treatments and the difficulty in reducing symptoms but this was not the case.
In this study, optimism could be considered for indicative purposes to be in the moderate range. Interestingly, optimism levels were similar in the 2 diseases studied and this may suggest that people suffering from either AxSpA or low back pain are rather less optimistic than a healthy population. Indeed, a study assessing optimism among 504 high school students reports a mean LOT-R of 16.5 whereas in this study, the mean LOT-R of the whole sample was 13.8 [
45]. Even though dispositional optimism is considered as a relatively stable feature of the personality over time and context, there are variations in optimism when people are prepared to face a threat and this indicates that for some people, optimism levels may vary [
46‐
48].
Optimism was related to mental HRQoL both in univariate and multivariate analyses in the present study. The link between moderate optimism and low quality of life might be explained by the role of coping strategies used by the patients. Indeed, it could be that less optimistic people use more dysfunctional coping strategies when confronting stressful events than optimistic people [
49‐
53].
The present findings were consistent with the previously published studies on optimism in the field of rheumatic diseases and chronic conditions [
22‐
24]. The largest study investigating the relationship between optimism and HRQoL in 1529 patients with chronic diseases found that optimism was positively linked with HRQoL [
23]. Similarly, Tsakogia and colleagues study [
22] investigated the influence of optimism on the HRQoL of patients with musculoskeletal problems and found that dispositional optimism was an independent factor affecting the mental composite score of the SF-12, and weakly (similarly to the present findings), the physical component of SF12. However, in comparison to these two studies, the mean LOT-R of our sample appeared lower.
In the present study, optimism had a very small effect on the physical HRQoL. These results indicate that optimism may not influence the interpretation of physical scores, widely used in the evaluation of AxSpA and low back pain.
The present study evidenced non-psychological drivers of PCS including global assessment for both AxSpA and low back pain patients, and BASFI for AxSpA patients only. These results confirm the validity of the study.
Applying the bio-psychosocial model to chronic diseases implies taking into account not only disease activity and severity, but also psychological aspects including optimism. We have shown optimism is a driver of psychological, but not physical, HRQoL in the 2 chronic diseases. However, further studies are needed to understand the pathway linking optimism to HRQoL and the potential factors playing a role in this relationship such as coping techniques.
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Authors’ contributions
All of the authors SK, AM, FB, SD, SF, CR, CH, FZ, SR, EP, BF; LG fulfil the following 4 criteria: Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; Drafting the work or revising it critically for important intellectual content; Final approval of the version to be published; Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The guarantors who accept full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish are for this paper, SK and LG. All authors read and approved the final manuscript.