| [Download PDF]
|Year : 2001 | Volume
| Issue : 10 | Page : 39--51
The impact of perceived tinnitus severity on health-related quality of life with aspects of gender
Soly I Erlandsson1, Kajsa-Mia Holgers2,
1 Department of Education and Humanities, University of Trollhättan/Uddevalla, Sweden
2 Department of Audiology, Sahlgrenska University Hospital, Göteborg University, Sweden
Soly I Erlandsson
Institution of Education and Humanities, University of Trollhättan/Uddevalla (HTU), Box 1240, S-462 28 Vänersborg
The Nottingham Health Profile (NHP) has been used to investigate the health profiles in different medical conditions. It has, however, never been applied to tinnitus sufferers. The present study aimed at investigating relationships between the perceived severity of tinnitus, audiometric data, age, gender and non-disease specific health-related quality of life measured with the NHP divided into two sections; NHP I (topics related to health status) and NHP II (health induced problems in daily life). These parameters were statistically analysed to identify predictive factors to the perceived severity of tinnitus, described by the Tinnitus Severity Questionnaire (TSQ). A total of 186 consecutive tinnitus patients (57 females and 129 males) attending an audiological specialist clinic in Sweden were included in the study. The stepwise regression model used explained 37.8 per cent of the variance in the perceived severity of tinnitus, and the significant predictors were: «DQ»Emotions«DQ», «DQ»Sleep«DQ», and «DQ»Pain«DQ», three of the six dimensions of the NHP I. Differences between gender were found in NHP II and age-related differences emerged in NHP I when male and female patients were compared to normal controls.
|How to cite this article:|
Erlandsson SI, Holgers KM. The impact of perceived tinnitus severity on health-related quality of life with aspects of gender.Noise Health 2001;3:39-51
|How to cite this URL:|
Erlandsson SI, Holgers KM. The impact of perceived tinnitus severity on health-related quality of life with aspects of gender. Noise Health [serial online] 2001 [cited 2022 Jun 24 ];3:39-51
Available from: https://www.noiseandhealth.org/text.asp?2001/3/10/39/31758
The severity of tinnitus, measured by psychological scales, has been found to correlate to a number of health problems, among them distress symptoms such as headache, dizziness and insomnia (Erlandsson et al., 1992; Dineen et al., 1997). Audiological factors also seem to be of some importance for the perceived severity of tinnitus, particularly the negative impact on hearing capacity (Hallam et al., 1988; Kuk et al., 1990; Hiller & Goebel, 1992; Holgers & Barrenas, 1996). Emotional factors are likely to influence the way the brain processes the information from the ear, as the auditory system has many connections with the limbic system which is involved in emotions (Jastreboff & Hazell, 1993). In comparison with normative samples, tinnitus complainers have shown higher mean levels of anxiety (Erlandsson et al., 1991; Halford & Anderson, 1991) and more negative mood states and depressive tendencies (Kirsch et al., 1989; Erlandsson et al., 1991). Tinnitus sufferers who were members of self-help groups reported problems such as irritation, annoyance, concentration and sleep difficulties, depression and despair (Tyler et al., 1983). Subsequently, there is strong evidence for presuming that quality of life is reduced in patients suffering from severe distress in relation to their tinnitus symptoms.
Measurements of health-related quality of life are increasingly being carried out as a supplement to medical examinations and as a reflection of carer satisfaction in different patient groups. Measures of health related quality of life could be subdivided into two types: generic and disease-specific. Generic questionnaires are nondisease specific, facilitating comparison of health status data among a large variety of specified diagnoses. An instrument of this character is the Nottingham Health Profile (NHP), which has been proven to be a reliable and valid instrument offering a satisfactory number of normative comparison data (Hunt et al., 1984; Hunt & Wiklund, 1987). The measurement of health status by the use of the NHP has been performed in samples of patients with a diversity of medical conditions; migraine (Jenkinson, 1990; O´Brien et al., 1993; Essinkbot et al., 1995), herpes zoster infection (Mauskopf et al., 1994), epilepsy (Jacoby, 1994), myocardial infarction and stroke (Wiklund, 1988; Wiklund et al., 1989; Visser et al., 1995), dizziness (Grimby & Rosenhall, 1995), and mental ill health (Gater et al., 1995). O'Brien et al. (1993) showed that the NHP was able to distinguish between patients with different levels of cardiac functioning. In the study by Mauskopf et al. (1994), the discriminant validity of the NHP was demonstrated by its ability to distinguish between different levels of pain severity in zoster patients. Jenkinson (1990) demonstrated that elevated NHP scores of migraine sufferers were gained for emotional reactions, sleep, social isolation and energy. These dimensions also had significant associations with the General Health Questionnaire.
An example of a disease-specific instrument is the 'Tinnitus Severity Questionnaire" (TSQ), a ten-item questionnaire, developed and evaluated by Coles et al. (1992). The TSQ was used in a clinical consecutive sample, reported by Erlandsson et al. (1992). Comparisons between the TSQ and a factor analytical solution (Tinnitus Handicap/Support Scale) of items regarding patients view on their tinnitus-related problems, perceived social support and perceived negative attitudes of others (relatives, friends) towards the subjects having tinnitus showed positive significant correlations with a number of items of the TSQ. These were quality of life, concentration difficulties, discomfort in quiet surroundings, ability to suppress tinnitus, anxiety/worry, tension/irritability and depressive reactions.
The NHP has recently been introduced to measure general health in tinnitus patients and has been suggested to be a useful tool when investigating the risk of developing incapacitating tinnitus (Holgers et al 2000). The questionnaire has also been used in an investigation of health-related quality of life on a group with profound hearing-impairment in Sweden (Grimby and Ringdahl, 2000). Subjects with impaired hearing in comparison with a normal hearing population reported, in general, lower health-related quality of life as measured by the NHP. Significant differences were obtained in three of the six dimensions of the NHP: lack of energy, emotional reactions and social isolation. Women with impaired hearing showed an overall tendency to score worse than the men in the study, a finding also in accordance with data obtained by normative controls.
The purpose of the present study was to investigate the impact of perceived tinnitus severity on health-related quality of life of a sample of consecutive patients attending a specialist audiological clinic in Sweden. In addition, our intention was to examine genderbased differences or similarities of health-related quality of life between tinnitus patients and a normative Swedish population sample.
Consecutive patients (N=186) consulting the specialist audiological clinic for tinnitus during a period of six months participated in the study. The gender distribution was 57 females (30.4%) and 129 males (69.6%). Of the female and the male subjects, 38% and 15% respectively were older than 65 years of age, which is the normal age for work retirement in Sweden. Standard audiometric assessments, i.e. mean hearing level for the left and the right ear; Pure Tone Average (PTA, 0.5, 1, 2 kHz) and PTA in the higher frequencies ( 3, 4, 6 kHz) differentiated between gender are shown in [Figure 1]. Tinnitus, which was the cause to their appointment, was more troublesome for the patient than the hearing loss.
Health-related quality of life was assessed with the Swedish version of the NHP (Wiklund, 1988). Two parts of health-related questions are included in the NHP, where part I, here called the NHP I, comprises six different dimensions: lack of energy (5 items), pain (8 items), emotional reactions (5 items), sleep (6 items), social isolation (6 items) and mobility problems (8 items). All together 38 yes/no questions are included in the NHP I. The second part of the NHP, here referred to as the NHP II, comprises seven yes/no statements referring to healthrelated problems in daily life. The higher the value, the more impaired health-related quality of life. The items of NHP I were weighted by McKenna et al. (1981), the designers of the instrument, using Thurstone´s method of paired comparisons (Thurstone, 1927). A number of patient and non-patient populations, in the age range of 19-80 years, participated in the normative studies. Only a few missing data on separate items exist in the matrix of the present study.
The severity of tinnitus was assessed with the Tinnitus Severity Questionnaire (TSQ) that includes 10 items, each yielding scores from 0 = not affected to 4 = always affected (Coles et al., 1992). The maximum score is 40. Example of an item in the TSQ is: "How often does tinnitus impair your concentration, for example when reading?".
The target group comprised 186 consecutive patients with tinnitus who were asked by letter to fill in two self-assessment scales (TSQ and NHP) mailed to their home address prior to the first appointment at the department of Audiology, Sahlgren's hospital. The patients were told to bring the completed questionnaire at the time of the group information meeting (their first tinnitus consultation) being held at the hospital. Of those who had been contacted 98 % returned the completed questionnaire.
Calculations, such as descriptives, group differences and multifactorial analyses were carried out by using Stat View, for the Mac Intosh computer. In order to identify possible predictors for the perceived severity of tinnitus a Stepwise Regression analysis was performed. The summed score of the ten items of the TSQ was used as the dependent variable and analysed in association with independent factors as health related quality of life (NHP I and II) and four hearing parameters (Pure Tone Average for low and high frequencies, left and right ear). Correlations were examined using the Spearman Rank Correlation.
The mean age of the female and the male subjects at the time of their tinnitus consultation was approximately 55 (SD: 18.2; age range: 21 - 86) and 49 (SD: 15.1, age range: 15 - 86) years respectively. The women were significantly older than the men were (p=0.015). Tinnitus severity assessed by the TSQ had a mean score of 21.3, indicating a moderately degree of tinnitus-related distress [Table 1]. There was no difference between the genders in tinnitus severity. Mean values of the females' and the males' scores were 21.0 (SD: 8.7) and 21.4 (SD: 8.1) respectively. As can be noted in [Table 1] the average values of the six dimensions of NHP I including the total sample were: Energy = 25.4; Pain = 11.1; Emotion = 24.0; Sleep = 27.2; Social isolation = 11.0; Mobility = 6.3.
The values, described in percentage of "yes-answers" of health-induced problems (NHP II) within the domains of occupation, ability to perform tasks around the home, personal relationships, sexual life, hobbies, social life, and holidays are presented in [Table 2]. It is clear that occupational life (Question 39) was perceived as significantly more problematic by the men than by the women in the study (p Hearing level and health-related quality of life
Correlations between hearing parameters (PTA left and right ear, at low and high frequencies), tinnitus severity (TSQ), the six sub-scales of the NHP I and the summed score of the NHP II were studied by the use of Spearman rank correlation analysis. The "Mobility" dimension of the NHP I had significant, positive correlations with two of the hearing parameters assessed; PTA low kHz, right ear: r = 0.23, p The NHP I, gender and age comparisons with normal control samples
[Table 1] demonstrates that there is a gender difference in four dimensions of the NHP I; Pain (p Predictive factors of the perceived severity of tinnitus
The summed score of the TSQ formed the dependent variable, "Tinnitus severity" in the stepwise regression analysis. Variables defined as independent were the six dimensions of the NHP I: "Energy", "Pain", "Emotion", "Sleep", "Social isolation", "Mobility", the NHP II (health-induced problems), and the four hearing parameters PTA (0.5,1,2 kHz) and PTA in the higher frequencies (3,4,6 kHz) for the left and the right ear. Three dimensions of the NHP I, "Emotion" (20.6 % explained variance), "Sleep" (11.2 %) and "Pain" (6.0 %) showed to be statistically significant predictors for tinnitus severity and explained 37.8 per cent of the variance. The independent variables: "Social isolation", "Energy", "Mobility" and NHP II did not give any significant contribution to the variance explained by this model, nor did the hearing parameters. Intercorrelations between the TSQ (dependent variable) and the three predictor variables showed rather high positive correlations between TSQ, "Emotion" (r= 0.51) and "Sleep" (r=0.48) and a somewhat less pronounced positive relationship between TSQ and "Pain" (r=0.29). All correlations were significant at the one per cent level.
Assessments, such as the NHP, can be used in different samples of tinnitus patients in order to obtain profiles of experienced health and quality of life in more general terms. In the present study, we found that in contrast to tinnitus severity, patterns of health-related quality of life were gender-related. Four dimensions of the NHP, pain, mobility, sleep, and energy, were perceived to be significantly more severe by the female subjects. It is interesting to note that emotional reactions are very similar in the male and the female sample. The findings that the work situation was experienced as significantly more problematic by the men and that the women regarded homework and holidays as areas of life that were more distressing seem to be in accordance with expectations of somewhat traditional gender roles.
Although the present study included consecutive clients only, the number of female subjects was approximately one third (30.4%) of the whole sample. Erlandsson (2000 a) observed in a review article on psychological profiles of tinnitus patients that in most instances, consecutive samples of tinnitus clinic patients included more men than women. We can only speculate around the reason for such a discrepancy. Women, in general, are more prone to express their emotional problems than men are, and seek more often help at psychiatric wards and ask for psychotherapy for their emotional disturbances. Also, professionals may regard women's complaints of tinnitus as related to depression and/or anxious mood. Therefore women more often than men are referred to a psychiatrist or a psychologist rather than to an audiological specialist by the general practitioner.
Perceived health-related quality of life was found to be worse for the tinnitus patients in comparison to matched control-groups. Judging these results, it is clear that tinnitus patients belong to a risk group for decreased well being in need of psychological support and therapeutic interventions. However, the small number of females with tinnitus in each age group necessitates further investigations in order to confirm the results of the present study.
Generally, the health status of the middle-aged women was rather similar to that of the youngest females. Younger males (25-34) with tinnitus reported less difficulties than middle-aged males did, and older men with tinnitus showed a significantly more negative profile in emotional reactions and sleep in comparison with controls. Somehow, the help-seeking middle- age male may feel that he is over the hill (midlife crisis) and that the demands on him are impossible to meet (Erlandsson, 2000 a). These findings call for a more comprehensive understanding of the patient's whole life situation, including general health and social factors in which tinnitus suffering only plays one part.
In the regression model, Emotion (composed of several items related to depression) was found to be the most important predictor variable, explaining 20.6 % of tinnitus severity. Emotional distress may give rise to cognitive distortions, like concentration difficulties in subjects complaining of tinnitus. Cognitive disturbances of individuals who are depressed are described and identified as problems in concentration, attention, sleep, learning and implicit memory (Eysenck and Mogg, 1992), the same complaints that tinnitus patients also tend to report. Sleep was the second most important significant predictor for tinnitus severity in the model. There is a large variation in the different studies regarding the percentage of subjects with tinnitus who report problems due to insomnia (McKenna, 2000). A complication is that insomnia is not very clearly defined in most investigations. In a study using a factoranalytical model, insomnia was judged as one of the significant strains related to tinnitus (Hallam et al., 1988). Different characteristics of personality problems have been linked to sleep disturbances, such as depression, anxiety, obsessive worry, and fear of losing control (Dineen Wagner et al., 1983).
Pain, the third significant predictor for tinnitus severity, appears to be more commonly experienced among the women than among the men. According to Erlandsson et al. (1992) frequency of headaches reported by tinnitus patients, is to some extent, age-related; younger subjects seem to experience significantly more prevalence of headaches than older subjects do. Depression has been mentioned as an affective correlate with headache (Cox & Thomas, 1981). Similarities in psychological profiles and level of depression between patients with chronic pain and patients with severe tinnitus were noted by Kirsch et al. (1989). In comparison with a sample of migraine sufferers including only women (Jenkinson 1990), the tinnitus patients (both women and men) in this study exhibit less severe NHP I profiles. This difference is particularly obvious in the domains of energy, pain, and social isolation. The notable discrepancy found between the two female samples (tinnitus & migraine) is in the dimensions of energy and mobility. Women with migraine perceived that they had less energy and women with tinnitus reported more mobility restrictions. The migraine sufferers were younger than the female tinnitus sufferers; approximately a difference of fifteen years in mean age.
The model of regression used in the present study explained 37.8 % of tinnitus severity, implicating that there are aspects of the patients' situation, other than those being included that might contribute to the variance of tinnitus severity in a significant way [Figure 2]. None of the four hearing parameters contributed significantly to the variance explained in tinnitus severity. However, there is a possibility that perceived hearing handicap in different demanding social situations would contribute to tinnitus being experienced as distressful. Two of the NHP I dimensions; mobility and pain had rather small but significant correlations with some of the hearing parameters, all of them in the low frequency range of the hearing levels assessed. There also seemed to be an overall impact of hearing on health-induced problems, as moderately high significant correlations between hearing and the NHP II were found. The impact of ageing on hearing as well as on healthinduced restrictions in daily life must also be taken into consideration.
Critical arguments of the NHP
Jenkinson (1991) has raised critical arguments on theoretical and empirical grounds relating to the NHP and its version with weighted items.
The author claims that the weighting of items by Thurstone's method of paired comparisons may be inappropriate. There is a very small variance of values for each statement within every topic domain of the NHP I. For example, the emotional reaction scale has weight values ranging from 7.08 to 16.21, which is not a large variance. Jenkins (ibid) suggests that Likert scaling may be a more appropriate method of scoring a health status questionnaire. In the present study, the NHP has been evaluated according to weighted items as this method has been introduced in the Swedish version of the scale not being questioned in any way in the Swedish manual.
Since patterns of health in patients with tinnitus are both age- and gender-related one might argue that tinnitus severity alone cannot cause the patients' perceived health problems. Decreased health-related quality of life was more prevalent in a consecutive tinnitus patient group than in the general population. Younger and middle-aged female patients exhibited most signs of negative health status in terms of lack of energy, pain or social isolation, emotional reactions and sleep disturbances in comparison with young and middle-aged female controls. There is a genderdifference in the general population, in the incidence of mental illness in age-group 25-55 years of age, where the occurrence rate is higher in women (Hagnell, 1970). These figures of occurrence are in accordance with the findings in our study, i.e. that younger and middle-aged women with tinnitus experienced more healthrelated problems than older women did when compared with normal age-matched control groups.
Throughout, the scores for males with tinnitus compared with normal control samples were higher for two dimensions: sleep and emotion. Sleep is one dimension of quality of life, which seems to play an important role in the pathogenesis of psychiatric illnesses (Billiard et al., 1994). Insomnia has been identified in a number of psychiatric disorders: Schizophrenia, mood disorders, anxiety disorders, panic disorders, alcoholism, and dementia. Individuals with insomnia are at risk for developing a psychiatric illness, as sleep disturbances not only is a consequence of psychiatric ill health but rather play a crucial role in the pathogenesis of psychiatric disorders (ibid). The most common psychiatric disturbances for women are depression and anxiety disorders, for men alcohol addiction (Ostlin et al., 1996). Several population studies from Europe and the USA show that the lifetime risk for developing a major depressive disorder is 12 % for men and 25 % for women. Also the anxiety disorders are more prevalent among women then among men. The prevalence, during one year, for panic disorder, agoraphobia, social phobia and generalised anxiety disorder is approximately twice as common for women compared to men.
In speaking with patients who feel annoyed by tinnitus, it is of importance to focus on relevant age- and gender-related factors. The life situation and the gender roles of women are different from those of men, which affects the divergent ways in which women and men manage an illness, and how they are received by the professional care-givers (Erlandsson, 2000 b). The role of gender for the subjective experience of tinnitus remains somewhat untouched as a topic of research. A gender difference in the perceived quality of the tinnitus sound has previously been observed by Meikle and Griest (1987) and by Dineen and his colleagues (1997). Women, more often than men seem to report a greater variety of sounds. We are interested in further investigating how the complexity of tinnitus sounds are linked to emotional aspects, aetiology and health-related quality of life as complex tinnitus seem to have a positive correlation with perceived tinnitus severity (Hallberg & Erlandsson, 1993).
For financial grants we are grateful to the Regional Health Authority in West Sweden, to the Swedish National Board of Health and Welfare and to The Swedish Council for Social Research.
|1||Billiard M., Partinen M., Roth T. & Shapiro C. (1994) Sleep and psychiatric disorders. J. Psychosom. Res. 38: Suppl 1.|
|2||Coles R.R.A., Lutman M.E., Axelsson A., & Hazell J.W.P. (1991) Tinnitus Severity Gradings: Cross-sectional studies. In Tinnitus 91, Proceedings of the Fourth International Tinnitus Seminar, Bordeaux, France, August 27-30. Aran J-M., & Dauman R. eds. Kugler Publications, Amsterdam/New York, p. 453-455.|
|3||Cox D., & Thomas D. (1981) Relationship between headache and depression. Headache. 21: 261-263.|
|4||Dineen R., Doyle J. & Bench J. (1997) Audiological and psychological characteristics of a group of tinnitus sufferers, prior to tinnitus management training. Br. J. Audiology. 31: 27-38.|
|5||Dineen Wagner K., Lorion R.P. & Shipley T.E. (1983) Insomnia and psychosocial crisis: Two studies of Erikson's developmental theory. J .Consult. & Clin. Psych. 51: 595603.|
|6||Erlandsson S.I., Rubinstein B., Axelsson A. & Carlsson S.G. (1991) Psychological dimensions in patients with disabling tinnitus and craniomandibular disorders. Br. J. Audiol. 25: 15-24.|
|7||Erlandsson S.I., Hallberg L.R-M. & Axelsson A. (1992) Psychological and audiological correlates of perceived tinnitus severity. Audiology. 31: 168-179.|
|8||Erlandsson, S.I. (2000 a) Psychological profiles of tinnitus patients. In Tinnitus Handbook, Tyler, R.S. ed., United States. Singular, Thompson Learning, p. 25-57.|
|9||Erlandsson,S.I. (2000 b) Tinnitus: ljud som barare av psykisk smarta (Tinnitus: sounds carrying psychological pain). In Delaktig eller utanfor. Psykologiska perspektiv pa halsa och handikapp. Carlsson, S.G., Hjelmquist, E., Lundberg, I. Eds., Umea, Sweden, Borea bokforlag, p. 105-125.|
|10||Essink-bot M-L., van Royen L., Krabbe P., Bronsel G.J. & Rutten F. (1993) The impact of migraine on health status. Headache. 35: 200-206.|
|11||Eysenck M.W. & Mogg K. (1992) Clinical anxiety, trait anxiety, and memory bias. In The handbook of emotion and memory: research and theory. Christianson S-A., ed. Lawrence Erlbaum Associates, Hillsdale, New Jersey, p. 429-446.|
|12||Gater R.A., Kind P. & Gudex C. (1995) Quality of life in liaison psychiatry. A comparison of patient and clinician assessment. Br. J. Psychiatry. 166: 515-520.|
|13||Grimby A. & Rosenhall U. (1995) Health-related quality of life and dizziness in old age. Gerontology. 41: 286-298.|
|14||Grimby A, Ringdahl A. (2000) Does having a job improve the quality of life among post-lingually deafened Swedish adults with severe-profound hearing impairment? Br J Audiol ;34(3):187-95.|
|15||Hagnell O. (1970) Incidence and duration of episodes of mental illness in a total population. Psych. Epidem. Hare E.H. & Wing J.K., eds. University Press, London.|
|16||Halford J.B.S. & Anderson S.D. (1991) Anxiety and depression in tinnitus sufferers. J. Psychosom. Res. 34: 1-8.|
|17||Hallam, R.S., Jakes S.C. & Hinchcliffe R. (1988) Cognitive variables in tinnitus annoyance. Br. J. Clin.Psychology. 27: 213-222.|
|18||Hallberg, LR.M. & Erlandsson, S.I. (1993) Tinnitus characteristics in tinnitus complainers and noncomplainers. Br J Audiology. 27: 19-27.|
|19||Harrop-Griffith J., Katon W., Dobie R., Sakai C. & Russo J. (1987) Chronic tinnitus: association with psychiatric diagnosis. J. Psychosom. Res. 31: 613-621.|
|20||Hiller W. & Goebel G. (1992) A psychometric study of complaints in chronic tinnitus. J. Psychosom. Res. 36: 337-348.|
|21||Holgers K.M. & Barrenas M.L. (1996) The correlation between speech recognition scores in noise in patients with no, mild or severe tinnitus. XXIII International Congress of Audiology, Bari, Italy, June 16-20.|
|22||Holgers K.M., Erlandsson, S.I. and Barrenas, M.L (2000) Predictive factors for the severity of Tinnitus. Audiology 39: 284-291.|
|23||Hunt S.M., McEwen J. & and McKenna S.P. (1984) Perceived health: age and sex norms in a community. J. Epidem. Comm. Health. 38: 156-160.|
|24||Hunt S.M. & Wiklund I. (1987) Cross-cultural variation in the weighting of health statements: a comparison of English and Swedish valuations. Health Policy. 8: 227-235.|
|25||Jacoby A. (1994) Felt versus enacted stigma: A concept revisited. Evidence from a study of people with epilepsy in remission. Soc. Sci. Med. 38: 269- 274.|
|26||Jakes S.C., Hallam R.S., Chambers C. & Hinchcliffe R. (1985) A factor analytical study of tinnitus complaint behaviour. Audiology. 24: 195-206.|
|27||Jastreboff P.J. & Hazell J.W.P. (1993) A neurophysiological approach to tinnitus: Clinical implications. Br. J. Aud. 27: 7-17.|
|28||Jenkinson C. (1990) Health status and mood state in a migraine sample. The International J. Soc. Psych. 36: 4248.|
|29||Jenkinson C. (1991) Why are we weighting? A critical examination of the use of item weights in a health status measure. S. Sci. Med. 32: 1413-1416.|
|30||Kirsch C.A. Blanchard E.B. & Parnes, S.M. (1989). Psychological characteristics of individuals high and low in their ability to cope with tinnitus. Psychosom. Med. 51: 209-217.|
|31||Kuk F.K., Tyler R.S., Russel D. & Jordan H. (1990) The psychometric properties of a Tinnitus Handicap Questionnaire. Ear. Hear. 11: 434-445.|
|32||Mauskopf J., Austin R. & Berzon R. (1994) The Nottingham Health Profile as a measure of quality of life in zoster patients: convergent and discriminant validity. Qual.Life Res. 3: 431-435.|
|33||Meikle M.B. & Griest S.E. (1987) Gender-based differences in characteristics of tinnitus. Hear J. 42: 68-78.|
|34||McKenna S.P., Hunt S.M. & McEwen J. (1981) Weighting the seriousness of perceived health problems using Thurstone's method of paired comparisons. I. J. Epidem. 10: 93-97.|
|35||McKenna L (200) Tinnitus and insomnia. In Tinnitus Handbook, Tyler, R.S. ed., United States. Singular, Thompson Learning, p. 59-82.|
|36||O'Brien B., Buxton M. & Patterson D. (1993) Relationships between functional status and health related quality of life after myocardial infarction. Med. Care. 31: 950-956.|
|37||Ostlin P., Danielsson M., Diderichsen F., Harenstam A. & Lindberg G. eds. (1996) KOn och ohalsa (Gender and ill health), Studentlitteratur, Stockholm.|
|38||Roth T., Kramer J. & Lutz T. (1976) The nature of insomnia: A descriptive summary of a sleep clinic population. Compare. Psychiatry. 17: 217-220.|
|39||Thurstone L.A. (1927) Law of comparative judgement. Psychol. Rev. 34: 237-286.|
|40||Tyler R.S. & Baker L.J. Difficulties experienced by tinnitus sufferers. J. Speech. Hear. Dis. 48: 150-154.|
|41||Wiklund I. (1988) Livskvalitet hos patienter med kardiovaskulara sjukdomar. Scandinavian J. Behav. Therapy. 17 (Suppl.): 87-98.|
|42||Wiklund I., Herlitz J. & Hjalmarson A. (1989) Quality of life five years after myocardial infarction. Eur. Heart J. 10: 464-472.|
|43||Visser M.C., Koudstaal P.J., Erdman R.A.M., Deckers JW et al. (1995) Measuring quality of life in patients with myocardial infarction or stroke: A feasibility study of four questionnaires in The Netherlands. J. Epidem. Comm. Health. 49: 513-517.|