Huntington’s disease (HD) is an inherited neurodegenerative disease involving motor, cognitive, and psychiatric/behavioral symptoms that will eventually affect work role functioning. Symptoms progressively worsen until full care is needed. The onset of motor symptoms and subsequent formal clinical diagnosis typically occur during the fourth or fifth decade of life, the age range when many individuals are at the peak of their professional careers. HD has a long presymptomatic period. Although most HD gene carriers are not clinically diagnosed until they experience motor signs, changes in cognition
1 and mental health
2 have been detected up to 15 years prior to formal diagnosis.
3,4 These cognitive and psychiatric symptoms can have a greater impact on function and quality of life than that of the motor symptoms.
5 Thus, the changes that occur in premanifest HD (preHD) may be crucial to a person’s ability to maintain day to day functions, including work functions and occupational status.
Numerous empirical studies have documented the value of employment in terms of financial reward, self-esteem, social support, personal satisfaction, community connectedness, and overall physical and mental health.
6 In contrast, extended work disability is associated with negative outcomes, including financial hardship, loss of self-esteem, social isolation, and increased mental health problems.
7 Work disability is associated with increased costs, such as health service provision; sick leave; and indirect costs due to the loss of work productivity, wage replacement, retirement, and disability pensions. The reduction or loss of the ability to work as a result of a neurological illness, including HD, has negative impacts on mental health, the family budget, and family dynamics.
8 It is therefore important that employment be maintained for as long as possible in individuals with preHD, who may eventually develop HD with progressive disablement. While studies have considered the potential for employer discrimination as a result of genetic legacy,
9–11 overall there has been a paucity of research that has considered the importance of employment in terms of preHD and, indeed, other neurodegenerative diseases.
Changes in work function may be one of the most reliable initial indicators of functional changes or decline in preHD.
12,13 Data from a small qualitative study of seven individuals with preHD and their family members suggest that work function may be compromised in preHD.
14 Beglinger and colleagues reported that occupational decline was common in those with preHD, with 65.1% reporting some loss of ability to engage in their typical work, as measured by the Unified Huntington’s Disease Rating Scale (UHDRS) Total Functional Capacity (TFC) scale.
12 However, individuals with preHD have reported that they can continue to be productive in their work environment when workplace accommodations can be made.
15 Identifying factors that may facilitate or hinder engagement in work-related functions would therefore enhance the ability to develop work accommodations that would enable preHD individuals to continue to maintain employment for as long as they wish and are able.
The aim of this study was to explore the predictors of work impairment and disability in a cohort of employed, preHD individuals. Given the lack of research in this area, the findings may inform the development of strategies or interventions to help preHD individuals maintain employment.
Discussion
This exploratory cross-sectional study investigated factors associated with workplace impairment and disability in a cohort of employed preHD individuals. In general, the study participants were cognitively healthy, had minimal motor symptoms, and were functioning well in terms of their mental and physical health, with no evidence of clinical depression, anxiety, or irritability. The proportion of participants reporting having missed work due to preHD was low (2.4%). However, around one in eight participants reported experiencing impairment while working, work-related activity impairment, and loss of overall work productivity due to their preHD. Several predictors of this workplace disability were identified. We found that good mental health was a consistent significant factor of all four outcomes. CAG repeat length and self-reported physical health were significantly associated with three outcomes: presenteeism, activity impairment, and work productivity loss. Increased anxiety and motor symptoms were also significantly associated with the Presenteeism and Work Productivity Loss subscales.
Based on the strength of the odds ratios and 95% confidence intervals, the results suggest that the predictors identified were not overly strong predictors of workplace disability (odds ratios are all between 0.84–1.18; 95% confidence intervals range from 0.79–1.32). However, these predictors were, importantly, statistically significant in a clinically healthy preHD sample; are clinically relevant; and have implications in the workplace. Based on the results, the strongest predictor of workplace disability outcomes was CAG repeat length, where nearly one in five individuals (14%−18%) with more CAG repeats had more odds of experiencing workplace disability in three domains of work productivity (impairment while working, activity impairment, and overall work impairment). CAG repeat length is inversely correlated with age of onset, and it may be that the preHD participants in this study reporting more workplace impairment were those nearest to clinical onset. Indeed, we found that having more motor symptoms was significantly associated with around 1 in 14 people having greater odds of impairment while working and reporting overall work impairment. This is consistent with the literature, as it is known that the motor disorder of HD is a major source of functional disability
29 and that disability is correlated with motor score.
30 This study group had an average of three symptoms, which suggests that even a small number of motor impairments can cause disability.
The results also suggest that work related impairment in this group can be predicted by a number of potentially modifiable factors. Self-report measures of physical health were significantly associated with three domains of work productivity, where around one in 16 people with better physical health scores had less odds of experiencing impairment while working, experiencing activity impairment, and reporting overall work impairment.
Self-report measures of mental health were significantly associated with all four domains of work productivity, with better mental health scores associated with 12% less odds to miss work time, 10% less odds to experience impairment while working, 10% less odds to experience activity impairment, and 10% less odds to report overall work impairment. One in ten people with preHD with higher levels of anxiety symptoms reported greater odds of impairment while working and overall work impairment. The domains of mental health measured included factors as vitality/energy, social engagement, accomplishments or limitations of emotional roles, and mental health, particularly depression and anxiety symptoms. Indeed, depression and anxiety are common, frequently coexist, and are leading causes of disability worldwide. They are important known causes of absence from work and permanent disability.
31Our results support previous literature in healthy populations, where depression and anxiety symptoms have been reported to increase the risk of early retirement.
32 The strongest association with retirement due to ill health has been found to be self-reported health status, and significant associations were found between depression, anxiety, and early retirement.
33 In terms of comparison with workplace disability in other neurodegenerative disorders, no other such disorder has the same scope of predictive genetic testing clinically available as HD, and assessing workplace disability preclinically is therefore challenging, with scarce published literature. Findings are consistent with the very limited HD literature, suggesting that work function may be compromised in the early stages of HD.
12,14 Our findings also support previous studies in Parkinson’s disease (PD), and a cross-sectional study in patients found that anxiety and older age were significant contributing factors for unavailability in the workforce.
34 Mental health in early PD has also been found to have a greater influence on the likelihood of individuals leaving the workforce than motor symptoms, with those with greater baseline depression, anxiety, and overall psychiatric distress more likely to stop working in a prospective study.
35Limitations and Future Research
The rates of the missing values for the four WPAI-SHP outcomes were all below 20%, which fall in the range reported for the majority of published psychological studies.
36 Since different missing data handling strategies have their own advantages and disadvantages and are based on different assumptions, and the missing data rates in general are acceptable,
37 we decided not to impute the missing data. Therefore, we adopted an available-case analysis approach, which we appreciate may bias the results and weaken the generalizability of the findings.
36 Additionally, due to the low number of events for each work disability subscale (and unbalanced outcome variables), some analyses lacked adequate power, including insufficient power to include interaction terms in the regression model. We were therefore unable to determine whether there were interaction effects and, if so, how they would affect the estimated associations. We were also limited in our choice of variables to those collected by the Enroll-HD study and might have missed important factors like job stress, job demands, and type of occupation that are significant predictors of work disability in other populations.
38This study relies on self-report data, which may be affected by the participant’s capacity for self-insight, often limited in the latter stages of preHD.
39 Future studies could collect collateral information from family members regarding functional changes in preHD, and also from employers (although this is often a sensitive area due to privacy and discrimination concerns). It would also be interesting to investigate the causal relationship between significant predictors and outcomes. The inclusion of the estimated time to onset (based on the CAG-Age Product score) would also be informative. A self-report work function measure specific for persons with preHD has been created—the HD Work Function measure
40—which distinguishes differences in work function between people with preHD and comparison participants, but so far has not been used widely in the field and is not included in the Enroll-HD protocol. This could be cross validated with the WPAI-SHP in future studies.
By using a pre-HD sample, we found that increased motor and anxiety scores were significantly associated with work disability. This suggests that motor and anxiety symptoms could be targeted areas for interventions in this group of individuals. However, since this is a single-group cross-sectional study, we were unable to determine whether the two symptoms were specifically relevant to pre-HD individuals compared with non-HD individuals. Future research involving both pre-HD and non-HD groups would help to establish this evidence. Future research should also investigate factors related to workplace disability in a cohort of symptomatic HD individuals. This would increase understanding of whether similar or different targeted strategies are needed to maintain employment given that these individuals are at a different stage of HD. Despite limitations, this study is an exploratory analysis that includes a large number of international participants. Results form the basis for future studies with more adequate sample sizes and power.
Implications for Individuals, Practitioners, Employers, and Policy Makers
This study identifies a number of key predictors of work disability-related outcomes due to preHD. Several of these key predictors are modifiable and are potentially responsive to interventions. For example, there exist effective pharmacological and nonpharmacological treatments for mental health disorders, particularly for depression and anxiety. Promotion of social support and engagement is now a target for workplace health interventions. Physical functioning, accomplishments, limitations of physical roles, extent of bodily pain, and general health can be boosted via lifestyle interventions, and asymptomatic preHD participants should thus focus on keeping physically healthy, ideally collaboratively with their healthcare providers.
Supporting people’s mental health and physical health, and the effective prevention and treatment of depression and anxiety, can be strategically targeted to help maintain preHD individuals in their work roles. Raising awareness via education and developing evidence-based effective health promotion strategies for this community will be key in any approach designed to delay workplace disability. Similar health promotion approaches are already being undertaken in other populations with the intention of delaying decline in the early or prodromal stages of neurodegenerative diseases, such as Alzheimer’s disease. This study emphasizes the importance of ongoing good physical and mental health in all workplaces, including implementing regular health checks as well as “work friendly” environments, which are strategies that support health, regardless of gene status.
Although HD is not considered a “common” disorder, HD is perhaps the most amenable of the dementias to early intervention, due to its genetic predictability and known biomarkers, allowing study in a definite preclinical, predementia phase. Thus, preHD can be used as a model to inform early-intervention strategies for more prevalent neurodegenerative disorders. Study results highlight issues that are becoming increasingly more topical, given that genetic testing has been extended to include testing for multifactorial diseases. Findings can be used to inform issues in other dementias that are becoming better determined and detected preclinically (e.g., Alzheimer’s disease, frontotemporal dementia).