The HUI-3 is a seventeen-item questionnaire measuring QoL and health states. HUI-3 can be applied in a wide variety of subjects, diseases, interventions and therapies. The following three different types of outcome measures can be derived: attribute levels, single- and multi-attribute scores. Attribute levels represent health states and are as follows: vision, hearing, speech, emotion, pain, ambulation, dexterity and cognition. Levels range from one (no disability) to seven (severe disability). Single-and multi attribute scores are derived from these attribute levels and range from 0 (dead) to 1 (perfect health). Single-attribute scores represent Health Related Quality of Life (HRQoL) per attribute level, while multi-attribute scores provide a general HRQoL value.

The amount of hours a day and days a week the CI is used.

The amount of hours a day and days a week the CI is used.

The amount of hours a day and days a week the CI is used.

The amount of hours a day and days a week the CI is used.

The amount of hours a day and days a week the CI is used.

The amount of hours a day and days a week the CI is used.

The NCIQ assesses the health-related states on psychological, physical and social domain in CI users based on 60-items formulated as statements. Those items are divided into six subdomains: basic sound perception, advanced sound perception, speech production, self-esteem, activity and social interaction. For every statement, except the last five statements, never (1 point), sometimes (2 point), often (3 points), mostly (4 points) and always (5 points) are possible response alternatives. The last five items represent the ability to perform a stated task. The following response alternatives are possible: no (1 point), poorly (2 points), moderate (3 points), adequate (4 points) and good (5 points). When the item is not applicable for the participants, the item can be marked as 'not applicable'. For every subdomain, the percentage can be calculated. A lower score indicates a poorer quality of life.

The AIADH is a 30- item self-reported questionnaire to assess self-reported disability in everyday hearing. The response scale for each item is a four-point Likert scale measuring how often the respondent is able to hear effectively in a specific situation (0 = almost always, 1 = frequently, 2 = occasionally, or 3 =almost never). Higher scores denote higher impairment.

The General Self-Efficacy Scale (GSE) was created to assess a general sense of perceived self-efficacy with the aim in mind to predict coping with daily hassles as well as adaptation after experiencing all kinds of stressful life events. The responses to the 10 items are made on a four-point scale, resulting in a final composite score with a range from 10 to 40. A higher score on the GSE indicates more self-efficacy.

The iMTA Medical Consumption Questionnaire (iMCQ) is a generic instrument for measuring medical costs. It includes 18 questions related to frequently occurring contacts with health care providers. The costs for each type of health care provider (i.e. primary, secondary, psychosocial, occupational, and complementary care) will be calculated as the sum of the amount of each resource used, multiplied by its associated unit costs. Costs for overall health care use as well as costs for health care use without hearing related contacts will be calculated, similar to Nachtegaal J, et al. Int J Audiol. 2010. Tariffs will be used as reported by the Belgian National Institute for Health and Disability Insurance (RIZIV-INAMI).

The Hospital Anxiety and Depression Scale (HADS) assesses anxiety and depressive symptoms and consists of fourteen statements respondents need to answer based on the degree to which the statement is true. Four response alternatives are given per statement, each corresponding with a score ranging from zero to three. The questionnaire is divided into two subscales; anxiety and depression, each comprising seven questions. Scores are calculated per subscale and range from 0 to 21. A score of zero to seven is considered normal, whereas scores of eleven or higher indicate presence of a mood disorder and scores ranging from eight to ten suggest a mood disorder could be present (borderline).

Need for recovery after work will be measured using the need for recovery scale, an six-item scale assessing the short-term effects of fatigue caused by work activities. It is a subscale of the Dutch questionnaire on the experience and assessment of work (VBBA, Vragenlijst Beleving en Beoordeling van de Arbeid). Four response alternatives are possible for each item: always (3 points), often (2 points), sometimes (1 point) and never (0 points). The total score on this subscale is between 0 and 18. A higher score indicates a higher need for recovery after work.

The Quickscan will be conducted in participants who are on sick leave. Based on 18 items with a six-point Likert scale from zero to five the need for guidance to improve the socio-professional reintegration can be identified. A higher score indicated a higher need for guidance.

The RBANS-H is a comprehensive cognitive test battery. The oral instructions and auditory stimuli of the RBANS are supported by written explanations and visual stimuli in the RBANS-H, which makes the RBANS-H usable for assessing patients with hearing loss. Five cognitive domains, i.e. immediate memory, visuospatial/ constructional, language, attention and delayed memory will be assessed with the RBANS-H using twelve subtests. The raw score for each subtest will be converted to norm scores using age-specific index score tables. Those index scores will be added up to obtain the total scale score of cognition which is convertible to an age-corrected standard score with a mean of 100 and a standard deviation of 15.

The Corsi Block-Tapping task will be used to evaluate the visuospatial short-term memory. During this test, nine blocks are presented on a computer screen where a sequence of blocks will light up. The participant has to designate the correct blocks in the correct order. Two different sequences of each block will be presented starting with two items for each sequence. When the participant can reproduce one of the two sequence correctly, one item will be added to the sequence. When the participant is not able to repeat either sequence the test ends. The amount of blocks in the last correct sequence will be the corsi span score. A higher score indicates a better visuospatial short-term memory.

The pure tone audiometry will be performed in a soundproof booth using insert-earphones, a bone conductor and a two-channel AC-40 audiometer (Interacoustics, Assens, Denmark). The modified Hughson-Westlake technique will be used to investigate the air conduction (AC) ear specific thresholds at 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 3000 Hz, 40000 Hz, 6000 Hz and 8000 Hz and bone conduction (BC) ear specific thresholds at 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 3000 Hz and 40000 Hz when the AC thresholds between 250 and 4000 Hz exceed normality levels (20 decibel hearing level (dBHL)). Afterwards, an unaided and best aided free field measurement will be conducted with the loudspeaker at 0° azimuth and a distance of 1 meter from the participant.

To investigate speech comprehension in quiet the Dutch NVA lists from the Dutch Society for Audiology (Nederlandse Vereniging voor Audiologen) will be executed. The list that consists of ten monosyllabic words composed of a consonant-vowel-consonant and one training word will be presented at 65 dBHL. Both a free field unaided and best aided measurement will be executed where the participant will be placed at 0° azimuth at 1 meter distance of the loudspeaker.

To evaluate the speech comprehension in noise an adaptive procedure by the Leuven Intelligibility Sentences Test will be executed in free field in two test conditions (unaided and best aided). One list of this SPIN-test contains 10 sentences. The same test set-up as the speech perception in quiet test will be used. For every test condition- the speech reception threshold (SRT) will be calculated as the average speech level of the last five sentences and the imaginary 11th sentence.