Hearing difficulties, ear-related diagnoses and sickness absence or disability pension - a systematic literature review

Hearing difficulties is a major public health concern [1‐5], estimated to be the ninth leading burden of disease worldwide in the year 2030 [4]. Partial or complete hearing loss as well as other ear-related diagnoses such as vertigo or tinnitus can have consequences for work capacity. Sick leave or permanent marginalization from the labour market in terms of disability pension due to these diagnoses are, however, not much discussed or studied, although interventions regarding this are warranted and need to be based on scientific knowledge [6].

Known causes of hearing difficulties include various factors such as age, noise exposure, heredity, infections, health, and socio-economic factors [7, 8]. Hearing difficulties as well as other ear-related diagnoses such as tinnitus, may lead to increased levels of stress, partly through the limited possibilities to be involved in ordinary conversions and the constant strain to hear [9]. This could potentially affect the risk of sickness absence and/or disability pension. Vertigo, balance related difficulties are also an important health problem that might lead to sick leave and exclusion from the labor market [10].

There are several indications of gender differences in the occurrence of hearing difficulties [9] as well as in sickness absence [11], why, gender stratified data regarding these aspects would be of interest.

Sickness absence has a large impact on society, employers, work sites, as well as on the individual and his or her family [6, 12]. As most individuals with a disease or an injury can work, sickness absence is seldom a good measure of morbidity on a population level [6], however, it is a good measure of the social consequences of morbidity in terms of work incapacity [6, 13]. In order to take adequate measures to prevent marginalisation among people with hearing difficulties, knowledge regarding the magnitude of such sickness absence and disability pension, is needed. Therefore, the aim of this study was to establish the current knowledgebase on hearing difficulties and other ear-related diagnoses and sickness absence and/or disability pension though conducting a systematic literature review of such studies.

The systematic literature review was conducted in accordance to the PRISMA guidelines [14], in the following five steps; searches for studies, assessment of relevance of identified publications, data extraction, categorization of studies and synthesis of results from included studies. The following inclusion criteria were applied: Studies presenting empirical data on hearing difficulties or other ear-related diagnoses as well as on sick leave or disability pension published in scientific peer-reviewed journals. Both self-reported difficulties as well as ear-related diagnoses were included, to provide a wide inclusion and try to capture disorders and difficulties, which if diagnosed, would fall in the chapter of “Diseases of the ear and mastoid process” according to the “International Statistical Classification of Diseases and Related Health Problems, Tenth Revision” (ICD-10) [15].

Studies were sought for in the following three ways, no language or time restrictions were imposed:

The searches were conducted independently by two persons (E. Friberg and K. Gustafsson). All identified publications were assessed for relevance according to the above inclusion criteria. Titles and abstracts were read independently by at least two authors. In case of uncertainty or disagreement, the full article was read and, if needed discussed until consensus was reached. All relevant studies were included, irrespective of their scientific quality. Information regarding study design, population, measures, data collection, analyses performed, and relevant results (where applicable, the most adjusted result was extracted) were extracted from the included studies. Thereafter, the studies were categorized with regard to study design, type of study group (i.e. population, employees, or patients), and outcome. Finally, results from the included studies were compiled.

When excluding double hits from different databases, a total of 2663 publications were identified, of which 18 were assessed as relevant (Figure 1), that is, they disclosed data on hearing difficulties or other ear-related diagnoses and on sick leave [10, 16‐28] and/or disability pension [17, 18, 29‐32] (Table 1). The included studies were conducted in eight different countries (Sweden, USA, UK, Germany, Netherland, France, Norway and Poland, Table 1). All included studies were published in English and only three were published before the year 2000 (Figure 2). The majority (56%) of the studies had a cohort design, five (28%) had a cross-sectional design, and three were intervention studies (Table 2).

There was considerable heterogeneity between the studies. Only four studies used population data, eight studies evaluated employed individuals, while six reported data on patients (Table 2). The hearing diagnoses/symptoms explored varied considerably between studies, including; sudden sensorineural hearing loss, otoaudiological diagnoses, unilateral vestibular loss, tinnitus, hearing impairment, Ménière’s disease, otitis media, vestibular vertigo, post-lingual hearing loss, vertigo, and ear and mastoid diagnoses. Data on hearing difficulties were in many of the studies self reported [10, 16, 19‐21, 28]. Outcome variables in the studies were different types of measures of sick leave and disability pension. Only four studies presented associations (i.e. rate ratios or odds ratios) between hearing difficulties and sick leave [20, 23] or disability pension [17, 18], respectively. Five studies presented data for patient groups [16, 19, 25‐27] without any control or comparison group. Several studies were based on very small samples, for example, only six studies included more than 1000 individuals [10, 17, 18, 29, 30, 32] and five studies included less than 100 individuals [19, 22, 24‐26] (Table 1). The mean number of participants was 3926. Only two studies presented data stratified by sex [17, 18] while six studies only included men [23, 25, 28‐31]. A majority of the studies presented data for all-cause sick leave instead of diagnoses-specific sick leave whereas half of the studies on disability pension assessed diagnoses-specific disability pension (Table 3).

The aim of this literature review was to summarize research results from published studies that present empirical data on hearing difficulties or other ear-related diagnoses and sick leave or disability pension. The most striking finding from this literature review is the low number of published studies about sickness absence or disability pension due to hearing difficulties/diagnoses, considering how prevalent such hearing difficulties are. Secondly, the vast incongruity of the results, which partly can be explained by the large amount of different exposures, outcomes and measures examined in the different studies. We could only identify 18 relevant studies to include in this review, in spite of using several different search methods. Moreover, there are remarkable few relevant studies published on associations (i.e. rate ratios or odds ratios), between hearing difficulties and sick leave [20, 23] or disability pension [17, 18], however, all the four studies with such data, reported positive associations. Only two studies reported data stratified by gender, both showing a higher risk of disability pension among women with sick-leave due to audiological [17] or vertigo [18] diagnoses compared to men. We found no studies that assessed hearing difficulties as an outcome, after, for example, sick-leave or disability pension. The extremely large variation of data on hearing difficulties and on sickness absence and disability pension means that, at this stage, it is not constructive to compare results from the different studies regarding risks for sick leave or disability pension.

The strengths of this study are the systematic approach in searching and assessing studies, including a large number of keywords and the employing of a wide search strategy in well-known literature databases. Another strength is that two researchers independently conducted the searches. The very wide search made it possible to identify studies about hearing difficulties or other ear-related diagnoses, sick leave, and disability pension from different scientific disciplines. However, we cannot rule out that we might have missed studies; some scientific journals are not included in the literature databases; for example, newly established scientific journals. Moreover, several studies only reported the information without this being the actual aim of the study in question, which increase the risk that we might have missed some studies. Furthermore, the risk of publication bias cannot be ignored, small studies showing no associations or inverse associations might not have been published at all. Nevertheless, the number of retrieved publications with this wide search strategy resulted in very few relevant studies which indicate that sick leave and disability pension with hearing difficulties or other ear-related diagnoses have not been widely studied in scientific contexts.

In areas where more studies have been conducted, usually only studies that have a minimum level of scientific quality are included in systematic reviews. It became evident that the number of conducted studies in this field did not allow for excluding studies of lower scientific quality. Instead, the aim was to use all available studies to gain knowledge, why all studies identified were included, irrespective of quality.

In conclusion, there are remarkably few studies published on associations between hearing difficulties or other ear-related diagnoses and sick leave and/or disability pension and there are very large variations between the studies regarding design, study groups, analyses, and outcome measures. Nevertheless, all studies that disclosed results on associations between hearing difficulties or other ear-related diagnoses and sick leave or disability pension reported positive associations. However, at this stage, these results cannot be considered to provide enough evidence for such associations. This finding warrants further attention and not only are more, but also better studies needed before any conclusions can be made. There is an overall lack of prospective studies with long follow-up investigating the risk of diagnosis specific sick leave and disability pension among individuals with hearing difficulties or other ear-related diagnoses. Also intervention studies targeting the workplaces more directly would be of great interest.