31st May 2013, Volume 126 Number 1375

Kayla Guitar, Ellen Giles, Bill Raymond, David Welch

In New Zealand, access to cochlear implantation for adults is limited.1 Adults must go on a waiting list with no advised date of surgery. Many remain on that waiting list for over a year, whilst knowing that an operation would likely provide them with many benefits: the mean time on the waiting list is around four years.

Position on the waiting list is subject to change because if new people are admitted to the list, they may be placed higher than existing applicants: position is based primarily on need as assessed by hearing disability. Waiting for medical intervention has been shown to increase stress2 and reduce quality of life.2

Thus, people on the cochlear implant waiting list are in a position that may be considered stressful. In addition to the stress of waiting, the effects of acquired profound hearing loss are also likely to be stressful.

Social isolation,3 tinnitus,4 grief,5 and embarrassment6 can all be consequences of hearing loss and may all result in stress. Further to this, a reduction in social support due to deterioration of interpersonal relationships may also diminish one’s capacity to cope with stress.7

Stress will lead to negative emotions and physiological arousal (Figure 1). This arousal, mediated by individual factors such as stress reactivity and recovery, and the effects of stress-related health behaviours, will lead to increased risk of physical and mental illness.

The development of a particular illness is affected by genetic predispositions, vulnerabilities, and previous illnesses or injury. Stress increases the risk of developing illnesses and can aggravate current illnesses:8 it has been linked to diabetes, asthma, arthritis, and depression, among others.9

That stress affects people with hearing loss is supported by findings of reduced health-related quality of life,10 increased depression,11 increased anxiety,11 and poorer physical health10 in this group.

After cochlear implantation, an alleviation of stress may be expected. Cochlear implants (CIs) have been associated with better health-related quality of life 12 and reduced symptoms of mental illness.13However, no published findings indicate whether the improvement seen with mental health extends to physical health.

The aim of this study was to investigate the health (physical and mental) of CI recipients and compare it to that of those on the CI waiting list.

Figure 1. The development of psychophysiological illnesses
Solid lines indicate the processes through which illnesses develop due to stress and the dotted lines show how outcomes may feed back into this process and contribute to the burden of stress. Adapted from Cohen, Kessler and Gordon.8

guitar1

Method

Participants—Two groups were compared: those on the Northern Cochlear Implant Trust (NCIT) waiting list for cochlear implantation and those who have received CIs through the NCIT or who are receiving follow-up care through the NCIT. A questionnaire was sent to all these individuals with approval from the Ethics committee of the University of Auckland (Ref no. 2010/199).
Candidacy for a CI depends upon having a bilateral severe to profound sensorineural hearing loss for their better ear and where hearing aids provide limited or no useful benefit. There is no maximum age for referral, and patients with additional needs are not excluded. Adults have normally acquired hearing loss post-lingually. In addition, the adults must be fit and well enough to undergo an operation. Of the 64 people on the waiting list, 44 (69%) responded.
The cochlear implant group consisted of adults who had received their implants at least 12-months ago, and were currently using, a cochlear implant through the NCIT, as well as those who had been implanted and funded by another provider (Accident Compensation Corporation (ACC) or private). Questionnaires were sent to 199 people for this group, and 119 (60%) responded.
Instruments—A questionnaire was created to investigate the presence and frequency of potentially stress-related, physical illnesses (Table 2): participants were asked to indicate how many days they suffered from symptoms of each condition in the previous year, thus creating variables that ranged from zero to 365; whether medication was used for each condition in the past year was also indicated. The 21-item Depression, Anxiety, and Stress Scale (DASS-21) 14 was used to assess mental health.
This questionnaire which has three scales: Anxiety, Depression, and Stress, and can also be used, as we have, to provide a total mental-health score.
Questions about demographics, general health perception (Question 1 from the Short Form health questionnaire (SF-36) 15), frequency of physician visits and sick days, and self-rated dissatisfaction with hearing (10-point scale; Figure 5) were also included. Furthermore, the following factors which may be associated with the relationship between stress and health were investigated: smoking,16 binge alcohol consumption,17 cohabitation,18 employment,19 and body mass index (BMI).20
The two groups were compared in terms of overall health measures. In principle, overall measures should better reflect the impact of stress than specific conditions because the latter would be more influenced by individual predispositions and vulnerabilities: by considering overall effects, the impact of stress should be revealed.
Overall health measures were: percentage of each group experiencing any potentially stress-related health condition (Prevalence), the number of days affected during the previous year (Persistence: N.B. to prevent an artefactual inflation due to Prevalence, Persistence was calculated as the mean days affected for those with any health condition—i.e. the total days affected divided by the number of conditions), and the percentage of those affected who took prescription medication (Medication).
Prevalence gives a measure of the overall health of each group, while Persistence and Medication Use provide evidence of the impact of the conditions.
Data analysis—Questionnaire data were analysed using Analysis of Covariance (ANCOVA) to allow comparison of the waiting list and CI groups while controlling for potentially confounding variables.
To explore the data further, where significant overall effects were observed, analyses were conducted at the level of the specific health conditions assessed. These were conducted using either t-tests (continuous outcomes) or Chi-squared tests (discrete outcomes). Since these analyses were exploratory and there was low statistical power due to the relatively low numbers experiencing each of the individual conditions, no attempt to correct type-I error rates for multiple testing was made.
Least-squares linear regression models for the two stressors (time on the waiting list and dissatisfaction with hearing) were established overall and for the waiting list and cochlear implant groups separately.
Four outcome measures were used: Prevalence (sum of conditions experienced), Persistence (average days affected), Medications, and DASS-total score. Stressors were included as predictors in separate models; all of these controlled for age, sex, living situation, and employment status.

Results

No significant differences in age (t[158]=.511, p=0.610), sex (Chi-squared [1, N=162]=1.207,p=0.179), living situation (Chi-squared [1, N=158]=.775, p=0.252), or employment status (Chi-squared [1, N=155]=1.444, p=0.154) were found between the two groups (Table 1).

Table 1. Demographic characteristics of participants by group
Variables

Waiting list
Cochlear implant
Age
Mean
60.2
(SD= 17.9)
58.6
(SD=17.3)
Sex
Male

Female
17
(39%)
27
(61%)
57
(48%)
61
(52%)
Living situation
Alone

With others
9
(21%)
34
(79%)
32
(28%)
83
(72%)
Employment (full or part-time)
Employed

Other
17
(40%)
25
(60%)
58
(51%)
55
(49%)

Those with cochlear implants had had their implant, on average, for 5.73 years (SD=4.93, Range: 375–6653 days) and they had, on average, spent approximately 9 months (mean=0.68 years, SD=0.67, Range: 8-1218 days) on the waiting list prior to their cochlear implant surgery. Those on the waiting list had been on the list, on average, for 18 months (mean=1.47 years, SD=1.18, Range: 45-1960 days).

Health—11% (n=4) of those on the waiting list and 6% (n=7) of those with cochlear implants were smokers (Chi-squared [6, n=158]=4.552, p=0.602). In regards to binge alcohol consumption, 27% of those on the waiting list and 28% of those with cochlear implants reported consuming five units of alcohol or more, on at least one day a week (Chi-squared [8, n=157]=8.307, p=0.404).

Of those on the waiting list, 55% were considered overweight or obese according to their BMI compared to 62% with cochlear implants (Chi-squared [2, N=146]=1.295, p=0.523).

Those on the waiting list visited their doctor an average of 6.2 (SD=4.8) times a year, whereas those using cochlear implants did so 4.3 (SD=3.7) times a year (t(151)=2.616, p=0.010). However, no significant differences between the two groups were found in days off work because of illness or bedridden days (both p>0.4).

General health—People on the waiting list were less likely to rate their health as very good or excellent and more likely to rate their health as poor, fair or good than people with cochlear implants (Chi-squared [4, N=157]=9.609, p= 0.048; Figure 2).

Figure 2. Self-rated general health perceptions of those on the waiting list for cochlear implantation compared to those with cochlear implants

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Prevalence of potentially stress-related health conditions—People on the waiting list reported experiencing an average of 5.8 (SD=3.01) different health conditions in the past 365 days whereas those with cochlear implants reported an average of 4.5 (SD=2.70) conditions, (F[1,161]=7.153,p=0.008).

This difference remained after correcting for age, sex, living situation and employment, (F[5,152]=5.525, p=0.020). The distribution of the number of conditions experienced in the past year is shown in Figure 3.

Within this, tinnitus (Chi-squared [1, N=160]=5.758, p=0.016); diabetes (Chi-squared [1, N=163]=7.705, p=0.006); CVD (Chi-squared [1, N=162]=4.324, p=0.038) and hypertension (Chi-squared [1, N=163]=5.272, p=0.022) were all significantly more common in those on the waiting list than in those with CIs (Table 2).

No conditions were significantly more common in the cochlear implant user group than in the waiting list group (all p>0.1).

Figure 3. Distribution of number of potentially stress-mediated conditions experienced by CI-users and people on the waiting list for a CI

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Persistence—When people on the waiting list were affected by a condition, they were affected for longer than those with cochlear implants (F(1, 152)=11.604, p=0.001).

The average number of days affected for those in the WL group was 164 days (SD=121 days) compared to 97 days (SD=103 days) for the cochlear implant group. This difference remained after correcting for age, sex, employment status and living situation, (F(1, 142)=11.970, p=0.001).

Additionally, digestive problems (t(69)=2.154, p=0.035), migraines (marginally) (t(24)=1.913,p=0.068); and tinnitus (t(65)=2.830, p=0.006) when experienced, occurred more frequently in the waiting list group than the cochlear implant group (Table 2).

There was no difference between the two groups for any of the other individual conditions (all p>0.1).

Medication—People on the waiting list, on average, took prescription medication for 3.1 (SD=2.4) conditions whereas those with cochlear implants took prescription medication for 1.8 (SD=1.9) conditions (F(1, 161)=12.602, p=0.001). This difference remained after correcting for age, sex, living situation and employment, (F(1, 146)=11.597, p=0.001).

People on the waiting list were more likely to take prescription medication for migraines (F(1,26)=4.984, p=0.034), ear infections (F(1, 19)=8.44, p=0.009), and sleep disturbances (F(1, 42)=9.990, p=0.003) than those in the cochlear implant group (Table 2).

Table 2. Specific health conditions
Health condition
Number Responding
Prevalence (%)
Persistence (Days)
Medication (%)
Waiting List
CI Users
Waiting List
CI Users
Waiting List
CI Users
Waiting List
CI Users
Tinnitus
42
118
60*
38
308*
199
12
2
Hypertension
44
119
48*
29
280
237
94
90
Digestive symptoms
44
118
48
48
135*
62
71
63
Cold
44
119
48
49
6
9
30
23
Back Pain
43
119
42
42
140
108
65
43
Joint Pain
44
119
39
35
214
158
50
40
Neck Pain
44
119
34
28
142
72
54
31
Arthritis
44
119
25
17
349
309
50
53
Sleep problems
44
119
25
29
236
174
55*
12
Migraine
44
119
25
14
72**
19
64*
24
Ear infection
44
119
23
13
45
11
100*
46
Diabetes
44
119
21*
6
320
243
89
50
Influenza
44
119
21
19
5
10
50
39
Asthma
44
118
18
9
105
40
100
91
Chest infection
44
119
18
9
74
23
71
82
Cardiovascular Disease
43
119
16*
6
365
268
100
100
Heart palpitations
44
119
14
8
105
32
50
33
Skin problems
44
119
9
6
219
218
100
86
Thyroid disorder
44
119
7
2
365
365
100
100
Irritable Bowel Syndrome
44
119
7
9
365
139
50
55
Cancer
44
119
7
2
¾
¾
¾
¾
Stroke
44
119
2
1
¾
¾
¾
¾
Ulcer
44
119
0
3
¾
365
¾
100
Colitis
44
119
0
1
¾
0
¾
100
Other
44
119
25
21
¾
¾
¾
¾
Note: Prevalence (Percentage of group with any potentially stress-related health condition), Persistence (mean number of days experiencing potentially stress-related health conditions), and Medication (Percentage of group using medication to treat potentially stress-related health conditions).
Asterisks indicate where the waiting list group had poorer health markers than the CI group.
*p<0.05; **p<0.01

Mental health—The proportion of each group meeting the DASS-21 diagnostic criterion for anxiety (Chi-squared [1, 158]=5.699, p=0.016), depression (Chi-squared [1, 158]=3.874, p=0.042), and stress (Chi-squared [1, 158]=5.347, p=0.023) was higher in those on the waiting list than in those using cochlear implants (Figure 4).

Total psychological distress, indicated by the total score on the DASS-21, was also increased in the waiting list group (Mean=22.9, SD =18.6) when compared to those with cochlear implants (Mean=15.4, SD=15.5), F (1, 156)=6.560, p=0.011. This difference remained after correcting for age, sex, living situation and employment, (F [1, 144]=5.678, p=0.018).

Figure 4. Percentage of each group meeting DASS-21 criteria for depression, anxiety, and stress

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Dissatisfaction with hearing—As would be expected, people on the waiting list had greater dissatisfaction with their hearing (Mann-Whitney U= 142.5, p<.001) than those on the waiting list (Figure 5).

Figure 5. Distribution of rated dissatisfaction with hearing for people on the waiting list and people with cochlear implants. A rating of 10 represents great dissatisfaction, and 1 represents complete satisfaction.

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Stressors prediction of health measures—Linear regression models controlling for age, sex, living situation and employment were run to examine the association between the potential stressors (Dissatisfaction with hearing and Time spent on the waiting list) and the four measures of health (Prevalence, Persistence, Medication, and DASS).

Dissatisfaction with hearing was associated with poorer health according to all four measures overall, but only with Persistence and Mental Illness in the CI group, and only (marginally) with Mental Illness in the Waiting List group (Table 3).

Time on the waiting list predicted greater Persistence and use of Medication overall, but was not related to Prevalence or Mental Illness, and was not associated with any of the health measures within the two groups separately (Table 3).

Table 3. Standardised linear regression coefficients (Beta) for the relationship between Stressors (Dissatisfaction with hearing and Time on waiting list) and Stress-related health measures. Models were run overall and for the CI and waiting-list groups separately. All models controlled for age, sex, living situation, and employment.
Variables
Dissatisfaction with Hearing
Time on Waiting List
Stress-related Health Measures
Overall
Cochlear Implant Group
Waiting List Group
Overall
Cochlear Implant Group
Waiting List Group
Prevalence
0.189*
0.047
0.071
0.075
0.050
-0.066
Persistence
0.288**
0.209*
-0.039
0.200*
0.125
0.052
Medication
0.217**
0.040
0.044
0.198*
0.063
0.122
Mental Illness
0.291**
0.296**
0.380~
0.063
0.019
-0.196
~p<0.1; *p<0.05; **p<0.01

Discussion

We showed that potentially stress-related health conditions had greater prevalence, illness persistence, and use of medications for in people on the waiting list. These findings are consistent with previous findings of an association between stress and illness.9

There was no a priori reason why waiting list candidates should have poorer health than CI users, and nor did controlling for potential confounding factors influence the effects; this implies that poorer health was attributable to the experience of living with acquired hearing loss and/or the experience of being on a waiting list for life-changing surgery.

Associations were stronger between dissatisfaction with hearing and the health measures, but time spent on the waiting list was also associated with health. This may imply that both are influential.

Prevalence, persistence, and medication—People on the waiting list had higher prevalence of stress-related conditions than those with a cochlear implant. The effects of stress on health vary between individuals, and may be mediated by predispositions such as genetics or previous illnesses.21

Thus, individuals who are undergoing similar stressors may develop different illnesses, and an overall indication of the total conditions experienced provides a stronger indication of psychophysiologically-mediated illness than any individual condition alone. Basing analyses on the total conditions also avoids potential statistical power issues associated with the rarer conditions.

Health conditions were more persistent in those on the waiting list. On average, individuals on the waiting list, when affected by any condition, were affected for 164 days compared to 97 days for those with cochlear implants. The findings are consistent with earlier research showing stress to aggravate current conditions and delay recovery from illness.22.

The greater use of prescription medication in the waiting list group also indicates reduced health for this group. The differences in Persistence described above may have been greater had it not been for the medication used.

Smoking and binge alcohol consumption—The poorer health of those on the waiting list could be directly due to stress, or could be indirectly influenced by health-related behaviours common in people under stress, such as consumption of too much alcohol or smoking.23 However, no differences were seen between the two groups in relation to smoking and binge alcohol consumption.

There were few smokers and binge alcohol drinkers in both groups, which is consistent with previous findings of low levels of alcohol consumption and smoking in the hearing-impaired population 24, and this gave only limited statistical power to detect any differences which may have been present.

Tinnitus—The rate of tinnitus was 60% in the waiting list group and 38% in the cochlear implant group. This difference of about one third is comparable to previous reports of decreases in tinnitus rates after cochlear implantation 25.

Tinnitus holds a particular place in the relationship between stress, hearing loss and illness. Firstly, as for many of the conditions, tinnitus can be caused by stress 26, and can also lead to stress,27resulting in a cycle of increasing illness and stress. Secondly, tinnitus can be caused by hearing loss4 or by stress.26 Furthermore, cochlear implantation could reduce tinnitus via activation of the auditory pathways4 or by reducing stress26.

Thus, unlike other conditions, there were two mechanisms that may cause and reduce tinnitus. This may explain why tinnitus was the most commonly experienced condition in the waiting list group (stress plus hearing loss) and was also the condition with the greatest reduction following cochlear implantation (reduced stress plus auditory pathway activation).

Mental health—Symptoms of depression and anxiety28 have previously been shown to improve following cochlear implantation. The current study adds further support for the mental health benefits of cochlear implantation as symptoms of all three facets (stress, depression, and anxiety) of the DASS were lower in those with cochlear implants than in those on the waiting list.

Dissatisfaction with hearing—Overall, dissatisfaction with hearing predicted poorer physical and mental health. This is consistent with the idea that impaired hearing would have an impact on health via isolation and frustration leading to chronic stress and thus impaired immune function.

The effects were less clear within the groups, but this would be explained by the reduced statistical power and the relative homogeneity of hearing within groups: the people on the CI waiting list all hear very poorly, so it is difficult to detect gradual effects amongst them.

Amongst the CI-users, there was rather more variability in functional hearing, and those who were still dissatisfied with their hearing also tended to have more persistent health problems and poorer mental health.

Time on waiting list—Overall, time spent on the waiting list was associated with more persistent health problems and greater use of medication, consistent with the idea that the waiting is stressful in itself. When psychophysiological changes persist through time, their effects add up and the risk of illness increases.29 Increased waiting times for elective surgery have previously been associated with increased mental distress.30

Implications of findings—The implications of this research are important: cochlear implantation is reliant on available funding (e.g. government, donations) because the cost of implantation and support is very high and is thus rarely covered by an individual recipient.

In New Zealand, public support of adult cochlear implantation is limited due to funding restrictions (for the Northern Cochlear Implant Programme, this has increased to 30 in the last 2 years). However, the increased presence and prolongation of illness in those on the waiting list will also burden the public health system. Thus, the true cost of cochlear implantation should take into account the consequent reduction of health system use and improved productivity.

Strengths and limitations—The main strengths of this research were that there were good and similar response rates for the two groups, and that the conditions assessed were all potentially mediated by stress. As far as we know, this is the first time that such differences have been observed in a CI/waiting list population, and the information may be valuable to policy-makers

It must be acknowledged that it is possible that some other factor(s) could lead to the observed differences in health. The research relied on self-report of health conditions, and those on the waiting list may have reported illness more readily than those with CIs for some unknown reason.

On the other hand, there was no obvious incentive for such behaviour, in that physical health state does not influence ranking on the waiting list, and the research was conducted independently and with anonymous questionnaires.

The research was cross-sectional and it cannot be ascertained that the health of the people on the waiting list was not already poor when they joined it. However, entry to the waiting list is permitted only if applicants are considered healthy enough to sustain an operation, and since entry to the waiting list is based primarily on hearing disability, there is no reason to suppose that the health, on entry to the waiting list, of current list members would have been poorer than those who have already received CIs.

Where present, associations between health measures and dissatisfaction with hearing and time on the waiting list were of the order of 0.2. These are small, but it must be borne in mind that our regression models controlled for potential confounding variables, and that many extraneous factors would be involved in influencing health. The effects are thus worthy of consideration, and the presence, rather than the magnitude of associations is of interest.

Finally, while the conditions we considered were potentially stress mediated, we had no physiological markers of stress in the waiting list group other than their physical illnesses, and future research measuring physiological stress markers in both groups would be useful.

Conclusion

The findings of this research are important for two main reasons: they demonstrate the impact of long-term stress on both physical and mental health, and they imply that living with significant acquired hearing loss while waiting for a cochlear implant is detrimental to health.

Funding for adult cochlear implantation in New Zealand is limited, leading to lengthy waiting lists. Reduction of the waiting list time for cochlear implantation may contribute to the reduction of stress-associated medical conditions in those who have lost their hearing and thereby reduce the burden on the health system.

Abstract

Aim

To investigate whether people on a waiting list for cochlear implantation are more likely than those who have cochlear implants to suffer from illnesses which are potentially mediated by stress.

Method

A questionnaire, designed to assess the presence, persistence, and medication use associated with stress-related illnesses, was administered to two groups: those on a waiting list for cochlear implantation and adult users of cochlear implants.

Results

Those on the cochlear implant waiting list had significantly poorer health as indicated by: a greater number of conditions experienced in the past year, longer illness length when affected by a condition, medication use for a greater number of conditions, and poorer mental health.

Conclusion

There are lengthy waiting lists for adult cochlear implantation. The need to wait and the lack of a known date for surgery, in combination with having a profound hearing loss is likely to result in chronic stress. Chronic stress may increase the risk of physical and mental illness via physiological systems which mediate response to environmental threats. Cochlear implantation may alleviate chronic stress in people on the waiting list, and these findings support the hypothesis that this influences physical health.

Author Information

Kayla Guitar, Educational Audiologist, Ministry of Education, New Brunswick, Canada; Ellen Giles, CI Rehabilitationist, Northern Cochlear Implant Programme, University of Auckland, Auckland; Bill Raymond, CI Audiologist, Northern Cochlear Implant Programme, University of Auckland, Auckland; David Welch, Senior Lecturer, Audiology Section, School of Population Health, University of Auckland, Auckland

Correspondence

David Welch, Audiology Section, School of Population Health, University of Auckland, Private Bag 92019, Auckland, New Zealand. Fax: +64 (0)9 3737496

Correspondence Email

d.welch@auckland.ac.nz

Competing Interests

Nil.

References

  1. Gunn RG. Adult cochlear implants in New Zealand-a chronic funding issue. The New Zealand Medical Journal. 2010;123(1321):9–12.
  2. Mahon JL, Bourne RB, Rorabeck CH, et al. Health-related quality of life and mobility of patients awaiting elective total hip arthroplasty: a prospective study. CMAJ. 2002;167:1115–1121.
  3. Gildston H, Gildston P. Personality changes associated with surgically corrected hypoacusis. Audiology. 1972;11(5):354–367.
  4. Gabriel D, Veuillet E, Vesson JF, Collet L. Rehabilitation plasticity: influence of hearing aid fitting on frequency discrimination performance near the hearing loss cut-off. Hearing Research. 2006;213:49–57.
  5. McKenna L, O'Sullivan A. Psychological aspects of acquired hearing loss. In: Graham J, Baguley D, eds. Ballantyne's Deafness. 7th ed. West Sussex: Wiley-Blackwell; 2009.
  6. Stephens SDG. Evaluating the problems of the hearing impaired. Audiology. 1980;19:205–220.
  7. Uchino BN, Cacioppo JT, Kiecolt-Glaser JK. The relationship between social support and physiological processes: a review with emphasis on underlying mechanisms and implications for health. Psychological bulletin. 1996;119(3):488–531.
  8. Cohen S, Kessler RC, Gordon LU. Measuring stress: A guide for health and social scientists. New York: Oxford University Press; 1995.
  9. Taylor SE. Health Psychology-International Edition. 7th ed. New York: McGraw-Hill 2009.
  10. Hogan A, Taylor A, Doyle J, et al. The communication and health needs of older people with hearing loss: Are hearing aids enough? Australian & New Zealand Journal of Audiology. 2001;23(1):11–18.
  11. Tambs K. Moderate effects of hearing loss on mental health and subjective well-being: Results from the Nord-Trøndelag hearing loss study. Psychosomatic Medicine. 2004;66(5):776–782.
  12. Looi V, Mackenzie M, Bird P. Quality-of-life outcomes for adult cochlear implant recipients in New Zealand. N Z Med J. 2011;124(1340):21–34.
  13. Knutson JF, Murray KT, Husarek S, et al. Psychological change over 54 months of cochlear implant use. Ear and Hearing. Jun 1998;19(3):191–201.
  14. Lovibond PF, Lovibond SH. The structure of negative emotional states: Comparison of the depression anxiety stress scales (DASS) with the Beck Depression and Anxiety Inventories. Behaviour Research and Therapy. 1995;33(3):335–343.
  15. Ware Jr JE, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Medical Care. 1992;30(6):473–483.
  16. Alberg AJ. Cigarette smoking: Health effects and control strategies. Drugs of Today. 2008;44(12):895–904.
  17. Grønbæk M. The positive and negative health effects of alcohol- and the public health implications. Journal of Internal Medicine. 2009;265(4):407–420.
  18. Dean A, Kolody B, Wood P, Matt GE. The influence of living alone on depression in elderly persons. Journal of Aging and Health. 1992;4(1):3–18.
  19. Evans J, Repper J. Employment, social inclusion and mental health. Journal of Psychiatric and Mental Health Nursing. 2000;7(1):15–24.
  20. Colditz GA. Weight, weight gain, activity, and major illnesses: The nurses' health study. International Journal of Sports Medicine, Supplement. 1997;18(SUPPL. 3).
  21. Heim C, Ehlert U, Hellhammer DH. The potential role of hypocortisolism in the pathophysiology of stress-related bodily disorders. Psychoneuroendocrinology. 2000;25:1–35.
  22. Dhabhar FS. Enhancing versus suppressive effects of stress on immune function: Implications for immunoprotection and immunopathology. Neuroimmunomodulation. 2009;16(5):300–317.
  23. Ng DM, Jeffery RW. Relationships between perceived stress and health behaviors in a sample of working adults. Health Psychology. 2003;22(6):638–642.
  24. Zazove P, Niemann LC, Gorenflo DW, et al. The health status and health care utilization of deaf and hard-of-hearing persons. Archives of Family Medicine. 1993;2(7):745–752.
  25. Bovo R, Ciorba A, Martini A. Tinnitus and cochlear implants. Auris Nasus Larynx. 2010.
  26. Henry JL, Wilson PH. The psychological management of chronic tinnitus. Boston: Allyn Bacon; 2001.
  27. Tyler RS, Stouffer JL. A review of tinnitus loudness. Hearing Journal 1989;42:52–57.
  28. Mo B, Lindbæk M, Harris S. Cochlear implants and quality of life: A prospective study. Ear and Hearing. 2005;26(2):186–194.
  29. McEwen BS, Wingfield JC. The concept of allostasis in biology and biomedicine. Hormones and Behavior. 2003;43(1):2–15.
  30. Oudhoff JP, Timmermans DRM, Knol DL, et al. Waiting for elective general surgery: Impact on health related quality of life and psychosocial consequences. BMC Public Health. 2007;7.