Work participation, mobility and foot symptoms in people with systemic lupus erythematosus: findings of a UK national survey

Employment is a key measure of self-worth, as it grants independence and social esteem. Non-participation in work is associated with poorer health, higher rates of consultation in primary care and higher rates of indebtedness and mortality [1]. Musculoskeletal disorders are one of the two biggest causes of long-term work absenteeism in the developed world [2]. Inflammatory rheumatic disorders in particular have been shown to be associated with high levels of work disability such that 20–70% of people with rheumatoid arthritis have become work disabled within 5–10 years of symptom onset [3].

Baker and Pope systematically reviewed the published studies of work disability specifically in people with systemic lupus erythematosus (SLE) in 2009 [4] reporting rates of work non-participation in 32.5%. However, the reviewers commented on a heterogeneous literature, measuring work non-participation in a wide range of different ways, and highlighted a need for more high-quality research in this area in order to adequately determine the prevalence and causes of work non-participation in people with SLE.

A recent study by Cherry et al [5] has demonstrated that lower limb and foot problems are highly prevalent among people with SLE. Previous work has also shown that these symptoms are associated with substantial morbidity and functional impairment [5‐9]; sixt-one% of people reported that foot pain adversely affected their lives [5]. However, to our knowledge, no research to date has specifically investigated the prevalence of, and relationship between, lower limb or foot related complications, poor mobility and work non-participation in people with SLE.

Therefore, this study seeks to explore the prevalence of self-reported work non-participation through SLE and foot symptoms in a sample of people living with SLE. The main aim and focus of the analyses was to explore potential associations between poor foot health and work non-participation.

One hundred and eighty-two people with SLE completed the questionnaire. Seventy-one of those 182 (39%) respondents were excluded as they were in neither a paid/ voluntary job nor long-term sick/retired due to SLE or foot problems. Statistical comparison of this group (n = 71) with the remaining 111 respondents for age in categories (in work most frequent age category = 4 (older); not in work most frequent age category 3; p < 0.001), duration of disease (in work mean duration 13 ± 9 (1–36) years; not in work mean duration 16 ± 10 (18–81) years; p = 0.596), and BMI (in work mean BMI 27 ± 5 (16–44); not in work mean BMI 28 ± 8 (18–42); p = 0.679), suggested that clinically the excluded participants were not significantly different but that they were older. This was not unexpected, given that these respondents are most likely retired due to age, not for a health reason.

Having excluded the 71, the remaining 111 respondents were eligible for further analyses of working status. Seventy-nine (71%) respondents reported that they were currently in paid or voluntary employment as compared with 32 (29%) respondents who reported work non-participation due to SLE and foot symptoms.

Comparison between those currently working and those currently reporting work non-participation showed no differences for ethnicity (p = 0.515) or BMI (p = 0.817) in univariate analyses, as shown in Table 1. Those who reported work non-participation were more likely to have a longer disease duration (p = 0.008) and there was a statistically significant effect of age between the groups (p = 0.048). When adjusted for age using multivariable logistic regression, duration of disease no longer remained a statistically significant factor (p = 0.132).

A comparison of people currently working with those reporting work non-participation is shown in Table 2. All foot symptoms were more frequently reported amongst those reporting work non-participation than those currently employed. After adjustment for age, those not in work were statistically significantly more likely to report previous foot ulceration (OR 3.47, 95% CI: 1.24–9.76, p = 0.018) difficulty walking (OR 3.15, 95% CI: 1.16–8.56, p = 0.024) and swelling of the foot/ankle (OR 2.91, 95% CI: 1.03–8.13, p = 0.041).

Overall, people those reporting work non-participation had higher mean MFPDI scores (18.13, 95% CI: 14.85–21.41) than those currently employed (10.16, 95% CI: 8.11–12.21) indicating more severe foot problems. Moreover, the same was found for each of the three MFPDI constructs (1. mobility, 2. pain, 3. personal appearance). After adjustment for age using a multivariate logistic regression model (Table 2) the MFPDI scores remained statistically significantly different across all constructs.

This study found that 29% of people with SLE eligible to work report work non-participation because of SLE and lower limb or foot problems. Moreover, comparison to those who are currently working with those who are not shows a greater number of a range of foot problems and significantly higher MFPDI scores. The only demographic factor associated with work non-participation within this dataset was age. However, work non-participation was associated with: ever having foot ulceration; swelling of the foot/ankle; and poor mobility/difficulty walking, even after adjustment for age.

Our finding that work non-participation affects at least 29% of those eligible to work is consistent with the results from other studies of people with SLE [4, 12‐14]. Demographic risk factors for work non-participation that have been identified by other researchers include age, ethnicity, lower educational attainment, lower social class, and disease-specific risk factors include disease duration, activity, pain, fatigue, depression, cognitive function, neuropsychiatric manifestations and damage [15]. To our knowledge however, no other study has explored the impact of foot symptoms on work participation and in particular, it would appear that poor mobility may have an important effect on work participation. As with other studies, our data are cross-sectional so that we are unable to draw conclusions about causation. However, it is of interest that high MFPDI scores and foot ulceration or swelling of the foot/ankle were significantly associated with risk of work non-participation and we suggest that future research about work participation in people with SLE should consider poor mobility and foot symptoms as well as other factors in prospective studies.

It is of interest that the MFPDI scores amongst those participating in work still suggest that foot symptoms are prevalent even when people are sustaining their work. This of course has important implications clinically, particularly if it can be demonstrated that baseline scores predict future work non-participation, which may allow for targeted personalised care planning. It suggests that foot health should receive greater emphasis within the clinic and that rheumatology clinicians should regularly ask about foot symptoms and examine the foot or involve podiatrists in the support of people with SLE.

It should be borne in mind that there were a number of limitations to this study. In particular, the numbers of participants eligible to work who reported work non-participation was relatively small and the study may have consequently been relatively under-powered. In light of that, it is in fact striking that statistically significant associations were identified for those reporting work non-participation. Moreover, because of the relative rarity of SLE as a condition, this is a large cohort when compared to the available literature on SLE and work participation. Another difficulty inherent in the design of this study was that no information is available as to the number of non-responders or their clinical characteristics or work participation. Consequently, we are unable to conjecture about the size or nature of any responder bias. It is possible that people with SLE who perceived themselves as having particular problems with their foot health were more motivated to participate than those unaffected by such symptoms. This study was designed to collect a minimum of personal information to reduce the burden upon respondents; however this does mean that there is limited information regarding disease severity or clinical manifestations that do not affect the feet. In contrast, a particular strength of this study is the clarity over the case definition of work participation that has been used. Baker and Pope [4] found this to be a very heterogeneous literature with wide variation in the types of case definition that had been used and it is important that research going forwards is consistent in choosing measureable and reliable measures of work participation.

To our knowledge this is the first study to examine the impact of foot symptoms on work amongst people with SLE. Twenty-nine% of people with SLE eligible to work reported work non-participation because of SLE and lower limb or foot problems. Our results suggest that foot health and poor mobility may be important contributors to a persons’ ability to remain in work although further prospective research is recommended. This work has important implications clinically, particularly if it can be demonstrated that baseline scores predict future work non-participation, which may allow for targeted personalised care planning. It suggests that foot health should receive greater emphasis and that clinicians should examine and discuss the impact of poor foot health or involve podiatrists in the support of people with SLE.