1. What is the prevalence of anxiety, panic fear and depression in adults with asthma, irrespective of their consultation history?

2. Is this prevalence significantly higher than that found in a general population survey of health and illness in the same General Practices and with UK normative data?

3. Are anxiety scores rather than depression scores elevated, compared with the general population, to support the suggestion of a specific relationship between asthma and anxiety?

4. Does the comparison of anxiety and panic fear levels with those in clinic-based samples suggest a selection bias of hospital attendance in previous research?

Throughout this paper levels of anxiety, panic fear and depression are reported as assessed using generally agreed cut-off points on established measures (HADS and ASC) and not as clinically diagnosed psychological disorders.

HADS anxiety and depression scores were compared with Crawford's community sample of 1792 UK adults 22. In Crawfords study HADS data were collected from 1792 members of the general adult population (females = 978, males = 810). Participants were recruited from a wide variety of sources including commercial and public service organizations, community centres and recreational clubs. The mean age of the sample was 41.5 years (SD = 15.9, range = 18–91). Each potential participant received an introductory letter, a HADS form and a form for recording demographic variables. The refusal rate was approximately 18%.

HADS depression scores were also compared with those of patients from the same General Practices, a subset of the Sheffield Health and Illness Survey (SHAIPS) 23. SHAIPS was a postal survey of a representative sample of the population of Sheffield looking at health status and use of health services and included the HADS depression scale. It was carried out two years after the survey reported here. The sampling frame used was the local population health register which contains, amongst other data, the GP with whom the person is registered. Stratification was used to ensure that the sample was representative of the Sheffield population in terms of age, sex and electoral ward. It is likely that some individuals responded to both surveys but the number doing so is unknown.

Data analysis was undertaken using SPSS software (version 10). The chi² test was used to compare proportions of clinically significant scores for HADS and ASC measures between men and women, chi² for trend for differences by age group, and Spearman's rank correlation was used to determine any relationship between continuous age and HADS/ASC score. Analysis of variance was used to compare HADS anxiety and depression scores with data from the UK and the general population of Sheffield. t-tests were used for comparison of means. Ideally, multiple regression analysis would have been used to determine whether there were differences in HADS depression by age and sex between the study population and the general population of Sheffield. However, as we did not have access to the SHAIPs raw data we undertook individual t-tests on each age, sex combination.

The investigators who collected and analysed the data reported to, and were advised by, a data monitoring group independent of the researchers.

461 completed questionnaires were received giving a crude response rate of 53%. After accounting for 89 questionnaires returned either undelivered or marked indicating that the recipient did not have asthma the adjusted response rate was 59%.

We had a higher proportion of responses from women – 38.3% of respondents were male and 61.7% female. This approximately reflects the sex distribution of the Sheffield population and a higher prevalence of asthma in women in Sheffield 23.

The mean age of respondents was 42.4 (S.D = 13.4) years, the median was 41 years and the range was 18–66 years. The % of respondents in each age group approximately reflects the age distribution of the Sheffield population except for a slightly lower response rate in the younger age group 24.

The proportion of patients with a HADS anxiety score of 10 or more was 31.6%. HADS anxiety score increased with age for both scores 8+ (chi² = 10.602, p = 0.031) and 10+ (chi² = 21.218, p < 0.001). There was no significant difference between men and women with respect to these proportions. However, there was a significant difference in mean HADS anxiety scores by sex (Mann-Whitney U = -2.916, p = 0.004). Women had a mean score of 8.2 (S.D = 4.5) compared with a mean score of 6.9 (S.D. = 4.3) for men. The proportion of people with asthma with anxiety at a level of possible clinical disorder (HADS anxiety score 8–10) is no different from the general population. However, the proportion with probable clinical disorder (scoring 11+), is double that in the general population. The cut off of 11+ is used here for direct comparison with UK normative data²². Mean HADS anxiety scores were also significantly higher for the asthma sample, compared with UK norms (Table 1).

The prevalence of asthma-specific anxiety from the ASC Panic Fear score was 15.7% (62/395). Women were significantly more likely than men to experience panic fear associated with asthma: 19.2% (46/239) compared with 10.6% (16/151, Mann-Whitney U = -2.498, p < 0.05). The mean panic-fear ASC score (S.D.) was 17.9 (8.5) overall and 16.7 (8.3) for men compared with 18.7 (8.7) for women. The range was 9 – 44. The mean score for women was significantly higher than that for men (Mann-Whitney U = -2.498, p = 0.012). There was a significant correlation between increase in ASC score and increased in age (r = 0.114, p < 0.05).

The results of this study clearly show that both the prevalence of anxiety and the level of anxiety experienced by people with asthma (as measured using the HADS) are higher than that of the general population. Almost one third of asthma sufferers experience anxiety at the level of probable clinical disorder, double that in the general population. The prevalence of anxiety is higher in women than in men with asthma and increases with age. A significant minority of people with asthma experience asthma specific anxiety as measured by the panic fear subscale of the Asthma Symptom Checklist. However, the fact that the prevalence of generalised anxiety and depression are high in this population indicates that anxiety experienced in asthma may be part of a broader picture of generalised psychological distress rather than indicating that panic has a specific role in asthma.

These results from a general population sample are important in that they support the evidence of panic reported previously for hospital attenders 1125, demonstrating that the findings are not only seen in hospital attenders but generally for people with asthma. Our findings are consistent with those reported previously. Rimington 13 found that 30% of patients with a diagnosis of asthma recruited through general practice had anxiety scores of 11 or more on the HADS suggestive of a clinical anxiety state, for inner city patients this rate was 40%. In the same study 10% of patients had HADS scores suggesting depression with mean scores (S.D) of 3.7 (2.7) and 6.0 (4.3) for suburban and inner city patients respectively compared with our findings of a mean HADS depression score of 4.72 (4.08). An Australian study 26 reported a prevalence of anxiety (scoring 8 or more on HADS) of 40% of patients with asthma. More-over the findings add weight to the evidence supporting increased levels of depression in asthma 14.

The results also corroborate the general findings of high levels of panic experienced by people with asthma reported in a recent review 1. Specific comparison of our results with other published studies is not straightforward as variations of the ASC panic fear subscale are used. The ASC mean scores reported in this paper are some-what higher than those reported for a comparable study 10 of asthma patients recruited from General Practice but the significantly higher levels in women compared with men is replicated.

That higher levels of anxiety and depression are associated with increasing age in the asthma population is interesting. In other chronic conditions psychological distress has been shown to decrease with age 27, as it does in the general population 28. The present findings may be explained by evidence that the level of depression experienced in asthma is related to the level of illness uncertainty 29. It may be that older people may feel more uncertain about managing their asthma. An alternative explanation may be that psychological distress increases with increasing duration of asthma as reported previously in men 30. However, the upper age limit in this study was 65 years so the older age group were somewhat younger than comparable studies 27.

In the present study, duration of illness was not recorded so that it is not possible to distinguish between association of asthma with age or duration of illness. It is also likely that a proportion of participants may have had Chronic Obstructive Pulmonary Disease which occurs from around 45+ years and has been shown to have a major impact on QOL and mood 31. This may explain the link between depression and age. In this study the GP diagnosis of asthma was not verified though the upper age limit was restricted to 65 as the likelihood of COPD increases significantly over 65 years.

A limitation of the study is that the sample was drawn from one UK city. Comparisons were made with data from the general population from the same GP practices indicating that the findings of psychological distress are related to the experience of asthma or chronic disease rather than being related to the specific location. However, a recent, comparable, community study reported a prevalence of 'possible' anxiety of 38% and 'probable' anxiety of 18.9% in people with asthma and prevalence levels of depression were no greater than controls 32. This was carried out in a relatively affluent rural, mainly Caucasian population, indicating that prevalence of psychological distress associated with asthma may vary with geographical and socioeconomic factors. An earlier study reported significant differences in the level of anxiety and depression experienced by people with asthma living in a suburban compared with an inner city location 13.

A further limitation is that no attempt was made to assess the prevalence of clinically diagnosed anxiety, depression or panic fear in the population.

A strength of this study is the relatively large sample size, however it is acknowledged that lack of information related to possible non-response bias is a weakness. Care was also taken to ensure that the socio-economic demographics of the practice populations reflected that of the city as a whole.

In our parallel study 33 into the management of anxiety in asthma, GPs had difficulties identifying clinically anxious patients. This indicates that anxiety related complications of asthma might not be recognised in general practice despite high prevalence levels. The screening tool used in this study could be used in both general practice and hospital clinics to identify patients with asthma experiencing levels of anxiety that may affect their ability to manage their asthma. Once such patients are identified, providing effective interventions to meet their psychological needs may pose a challenge to community services. Further research is needed into effectiveness of interventions to help people with asthma manage the associated psychological distress, particularly interventions which can be delivered by those staff already in contact with patients such as the asthma clinic nurse.