Does the EQ-5D usual activities dimension measure what it intends to measure? The relative importance of work, study, housework, family or leisure activities

Nowadays, the Euroqol 5-dimensional questionnaire, usually termed as EQ-5D, is the most widely used generic preference-based health-related quality of life measure [1‐3]. Although EQ-5D has been developed to produce a preference-based index for economic evaluations, it has been widely used across different settings, such as individual health status for use in clinical settings, observational studies, population health surveys [3]. The EQ-5D descriptive system initially comprised of six dimensions that included two dimensions asking respondents to report problems with: (i) ‘Main activity’ i.e., able to perform main activity (e.g., work, study, housework); and (ii) ‘Social relationships’ i.e., able to pursue family and leisure activities, as well as the other four dimensions of the current version of EQ-5D (mobility, self-care, pain/discomfort, and anxiety/depression) [4]. However, the initial experimentation with this six-dimensional version resulted in the merging of ‘Social relationships’ with ‘Main activity’ dimension that became the current ‘UA’ dimension, which leads to the present five-dimensional questionnaire. This change was accompanied by an explicit description of the UA dimension as work, study, and housework alongside family and leisure activities [4]. There was a broad agreement amongst the EuroQol group that the UA dimension would cover the described daily activities, where ‘usual’ was perceived as referring to some frequency or regularity of performance of the activities [5].

Nevertheless, practitioners have raised concerns about the UA dimension due to either respondents’ perceived ambiguity when interpreting the UA dimension or respondents’ counter-intuitive responses [5]. Selai [5] summarized possible sources of ambiguity, including semantics (usual/unusual may refer to regularity/frequency or to normal versus abnormal); vague quantifiers (relative frequency conveys different meaning depending on race, education, and age); and the double or multi-barrelled nature of the question (e.g., how to answer if you cannot work but do not have any problems doing leisure activities like reading or playing chess). Furthermore, in adaption to long-lasting chronic illness, one’s usual activities that were initially affected by the disease become less regular and replaced by new daily or frequent activities through activity adjustment [6]. This might make the UA dimension especially prone to adaption that would potentially affect the responses of individuals with chronic conditions.

In general, the UA dimension is thought to measure both activities and social participation [7, 8]. However, there is mixed evidence from the literature. For example, research among stroke patients suggested that the UA dimension was measuring social functioning [5, 9], while a study among patients with diabetes indicated that the UA dimension measure limitation with work but not social activities [10]. Lin et al. [11] also showed that UA dimension correlated strongly with subscales on the Patient-Reported Outcome Measurement Information System (PROMIS), such as physical function, fatigue, and satisfaction with social roles. It has also been suggested that interpersonal relationships might be important as a bolt-on dimension [12, 13].

Moreover, evidence showed that the UA dimension is associated with both physical and mental aspects of health, but more strongly with the former. For instance, using data comprising seven disease groups and a non-diagnosed healthy group, Gamst-Klaussen et al. revealed stronger correlations between UA dimension and the other EQ-5D dimensions that tap physical health (i.e., mobility, self-care and pain/discomfort) than with anxiety/depression [14]. A similar result was found in a study among individuals with COPD [11]. A study that described the most commonly reported EQ-5D health states using SF-36 in the general Swedish population showed that moderate problems on EQ-5D UA dimension most strongly affected the SF-36 role limitations scales due to physical health problems [15]. A comparison of SF-12 and EQ-5D administered in the US general population also demonstrated that the UA dimension had a stronger relationship with the SF-12 physical health component than the SF-12 mental health component [16].

Summary statistics of the variables were presented in Tables 1 and 2. Almost 65% of individuals reported no problems in doing their UA activities, while those with no problems in family, housework, leisure, and work/study activities was 66.7, 49.3, 30.7, and 26.4%, respectively. The mean age of respondents was 51.46 (SD = 15.41) years, and ranged 18–93 years. Data were fairly gender-balanced (52% female). Most respondents had a diploma or university degree (68%), the majority lived with a partner or spouse (64%), and the distributions of chronic diseases were fairly balanced in the sample.

The Spearman correlation coefficient between the UA dimension and the main predictors were quite high: with work/study (rho, ρ = 0.63), housework (ρ = 0.66), family (ρ = 0.57) and leisure activities (ρ = 0.63). The Spearman’s correlation coefficient tends to yield a better correlation estimate than a Pearson product-moment correlation applied to ordinal variables, especially when the distribution of the ordinal variables is skewed.

The regression results were presented in Table 3. All main predictors, including work/study, housework, family, and leisure activities were significant (p < 0.001) determinants of UA dimension. For instance, results from the LRM revealed that the odds of having problems in UA was 12 (= e^2.5) times higher for those who are unable to do the housework tasks than those who are able to do the housework tasks very quickly. Similarly, OLS results showed that being unable to do most or none of the housework tasks without help leads to 0.85 higher problems in doing UA as compared to those who can do housework tasks very quickly. In the OLS, being ‘slightly limited’ to do leisure activities reduced UA by 0.6-percentage point as compared to ‘not limited at all’ but was not statistically significant; however, the LRM significantly picked up the difference. Among control variables, having a chronic condition significantly determined UA. Both LRM and OLS models generally produced similar results in the sense that in both models the regression results showed the same directions. Both models also produced similar ranks with regard to the importance of activities that describe the UA dimension (as detailed in the next paragraph). Results from the cancer sample with a more precise definition of leisure variable demonstrated similar results (Online Appendix Table A1), and so does the proxy variable for work/study (Online Appendix Table A2).

Figure 1 and Table 4 summarize the relative importance of each predictor for UA dimension of EQ-5D. The overall goodness-of-fit was over 49 and 63% in LRM and OLS, respectively. Housework, leisure, work/study, and family activities significantly contributed to the total explained variation in the UA dimension, in that order. For instance, the respective marginal contribution of housework, leisure, work/study, and family activities to UA dimension (as a share of goodness-of-fit) was 28.0, 26.2, 20.8, and 14.7% in the LRM. Similar results observed in the OLS regression model: housework contributed the highest (28.7%) followed by leisure (24.1%). Family activities contributed the least (17.9%).

Figure 2 and Online Appendix Table A4 summarized the relative importance of the main predictors of UA dimension across the healthy group and disease groups. The relative importance rankings were quite similar across different groups. Housework was the most important variable except in the arthritis group, where leisure contributed most. Family activities consistently ranked least except in the healthy group where work/study and family activities switched importance rankings. In addition, the depression group differs in two ways: first, control variables were most strongly associated with the UA dimension; and second, it had the lowest goodness-of-fit (i.e., R² = 38%). It is also worth mentioning that the marginal contribution of work/study exceeds that of leisure in the depression group alone.

This study investigated whether the EQ-5D usual activities dimension reflects measures of variables related to work/study, housework, family, and leisure activities as described in the questionnaire. The findings suggest that respondents consider these wide ranges of activities when reporting on how their health affects their UA, and hence the UA dimension measures what it intends to measure. Inquiry into relative importance revealed that housework explains most of the overall variance, followed by leisure, while family activities ranked last.

This sequence of importance ranking was consistent across the majority of disease groups as well as the healthy group, with housework at the top. This finding suggests that problems with housework are more salient and possibly more difficult to adapt too. That is, change in some activities might be less obvious to the individual (e.g., leisure activities change from playing squash to playing chess), but it is difficult to adapt to an inability to do basic housework activities like preparing food or cleaning the house. Another reason for the dominant role of housework might be that the term “usual” is commonly understood as “daily” by respondents [25], which could make other non-daily regular activities (e.g., problems playing golf once a week or meeting family once a month) less likely to be reported when considering one’s usual activities.

Compared to family activities, housework activities contributed twice as much of the overall variation. The possible explanation for the lower contribution of family activities could be an overlap with housework and leisure activities. In the description of the EQ-5D UA dimension, there is no clear definition as what a ‘family activity’ means. Thus, respondents may attribute some of the activities related to family as housework or leisure activities. In fact, it is difficult to draw a line of demarcation between family activities and housework or leisure activities. For instance, cooking can be both housework and family activities as well as leisure activities. Moreover, people may understand family activities as social phenomena instead of usual activities that are more physical, such as housework, which would be in line with the original EQ-6D that described family and leisure activities under the social relationship dimension [4].

The leisure variable is the second-most important for UA dimension that even exceeds the contribution of work/study. The reason why the relative importance of leisure activities generally exceeds that of work/study is most probably that leisure activities extend from the very informal and casual to highly organized and long-lasting activities, while work/study are specific and well defined for each individual.

In the healthy and disease groups, the relative importance ranking of the main predictors of UA dimension was consistent except in the arthritis group. In the arthritis group, leisure activity was most important, followed by work/study, housework, and family. This result can be explained by the nature of the disease and the way the leisure variable was described. That is, the leisure activities variable focuses on the ability to do vigorous activities such as participating in strenuous sports or lifting heavy objects, as well as moving a table or pushing a vacuum cleaner, which are activities that might be especially challenging to individuals with arthritis. In contrast, in the depression group, leisure, and work/study activities switched importance rankings. This result is likely because of the nature of the leisure variable; leisure is tapping health that is more physical. However, the items used to measure work/study include items that explicitly emphasize emotional problems (i.e., feeling depressed or anxious), which could increase the contribution of work/study in the depression group. For instance, a separate regression analysis (not reported here) with work/study activities as two separate variables (emotional health and physical health) revealed that only the latter significantly affect the UA dimension, suggesting that respondents mainly focus on their physical health when reporting problems on the UA. Furthermore, although depression affects motivation to do usual activities, both housework and leisure (as described in this study) are mostly measuring a physical concept. Lastly, for the healthy sample, housework and leisure activities continued to contribute the lion shares to the UA dimension, and work/study activities interestingly ranked last. However, this is not surprising, considering healthy people are usually less concerned about their work/study compared to people with chronic conditions.

It seems evident that the term usual is understood as activities that are performed with some regularity [25]. Thus, one area of ambiguity is the notion of how ‘regular’ is ‘usual’; i.e., the ambiguity in the interpretation of the term ‘usual’ lies in whether ‘usual’ mean ‘daily’ or ‘regular’ (e.g., visiting families every week-end). Another area of ambiguity is whether ‘usual’ covers ‘role’ or other activities, and whether the individual is fulfilled or not, particularly in reference to activities preceeding illness [25]. Furthermore, Rand-Henriksen et al. compared hypothetical and experience based EQ-5D valuations and argued that usual activities could be the least tangible dimension for the general public [26]. The issue of valuation of EQ-5D health states is beyond the scope of the current study; however, the ambiguity in the interpretation of the term ‘usual’ in the UA dimension could complicate the valuation exercise and warrant future studies.

This study has a number of limitations. One limitation is the measure of leisure variable from the SF-36 questionnaire. As discussed, these items measure mainly vigorous activities (e.g., participating in strenuous sports), and has some overlap with housework. Nevertheless, our findings are consistent with a more precise measure of leisure (obtained from the QLQ-C30 instrument). Another limitation could be the lack of a clear distinction between the described activities, such as housework, leisure, and family activities, which highlights the challenge using such a multi-barreled question to measure usual activities. Further, not all variation in UA dimension is accounted for by the explanatory variables used in this study. This indicates that additional activities other than those described here are important for variation in UA. However, the four major activities alone explained over 44 and 59% of the variation in LRM and OLS, respectively, which is quite large in this kind of social study. Lastly, respondents volunteered to participate in the MIC study, something which might lead to self-selection bias. Despite these limitations, this is the first study that has empirically attempted to test whether these activities, in fact, reflect the UA dimension of EQ-5D. Future studies should apply better measures of work/study, housework, family and leisure activities that can minimize conceptual overlap between these variables. Further studies would also be required to identify other important predictor(s) of the UA dimension, which can give insights into what respondents are considering when they report problems on this dimension.

In conclusion, the UA dimension fairly picks up the described activities, such as work/study, housework, family, and leisure activities. In explaining the variation in the UA dimension, housework is relatively most important, followed by leisure, while family is the least important. In a nutshell, the UA dimension of EQ-5D captures what it intends to measure.