Introduction [back to top]
Traditional measures of disease impact, such as prevalence and mortality rates, are important but are of limited use in understanding the extent of the effect a disease has on an individual. ‘Health-related quality of life’ (HRQoL) is a term often used to describe an individual’s perception of how a disease or condition affects their physical, psychological (emotional) and social wellbeing. This can be used to measure the impact of asthma on a person’s health and everyday functioning. Generic measures of quality of life are frequently used in health surveys to evaluate the overall impact of a person’s health status on their health and everyday functioning.
Among people with asthma, disease severity, the level of disease control and the impact of the disease on HRQoL are interrelated. People with severe asthma can be expected, on average, to have worse outcomes and, hence, worse HRQoL than people with less severe disease. During periods of poor asthma control, people with asthma report poorer HRQoL (Vollmer et al. 1999). A number of aspects of the physical impact of disease and its effect on social functioning or role performance can also be considered as markers of disease control. These include reduced activity days, restricted physical activity, reduced functioning ability and days lost from work or school.
This chapter presents information on HRQoL using data from the ABS NHS and state health surveys. Comparisons in HRQoL are made among people with and without asthma and the impact of asthma on overall, social, emotional and physical wellbeing are described.
8.1 Impact of asthma on self-assessed health [back to top]
The presence of asthma is associated with worse self-assessed health status (Table 8.1). In the ABS 2004–05 NHS, 42% of adults with asthma rated their health as ‘excellent’ or ‘very good’, compared with 58% of people without asthma. At the other end of the scale, 27% of people with asthma rated their health as ‘fair’ or ‘poor’ compared with only 15% of people without the condition.
Although the definitions of asthma varied, in all surveys listed in Table 8.1, the distribution of responses on self-assessed health status was shifted towards a more adverse health status among people with asthma.
This relationship also exists among children. Data from the Victorian Child Health Survey show that parents of 73% of children with asthma compared with 91% of children without asthma reported that their child’s general health was ‘excellent’ or ‘very good’.
The disparity in self-rated health status between people with and without asthma increased with increasing age among both males and females (Figure 8.1). Females with current asthma rated their health marginally better than males with current asthma, particularly among those aged 15–34 years.
8.2 Impact of asthma on the domains of HRQoL [back to top]
Health-related quality of life measures are commonly described in terms of physical, psychological and social domains. Available evidence suggests that in all these domains the HRQoL of people with asthma is worse than that observed in people without the disease. Here we review data on the impact of asthma on the psychological and social domains of HRQoL.
8.2.1 Psychological domain
The psychological component of quality of life encompasses thoughts, emotions and behaviours. Asthma has an impact on this domain of quality of life.
In a South Australian study, people with asthma had a higher prevalence of depression than people without asthma (Goldney et al. 2003). Furthermore, people with more severe symptoms of asthma (shortness of breath, waking at night with asthma symptoms or morning symptoms) were more likely to suffer from major depression than those without severe symptoms.
General measures of the psychological component of quality of life (such as the mental component summary of the SF-12 Health Survey—12-item short form) are able to detect small differences in the psychological health of people with and without asthma. Specific measures of anxiety and depression, such as the Kessler Psychological Distress Scale, have been used in surveys of people with and without asthma. In this section, we present Australian data from both generic and specific measures of the psychological component of HRQoL and compare these among people with and without asthma.
Some studies have found worse mood and higher levels of anxiety and depression in people with asthma compared with people without asthma (Table 8.2)
In the general population, females were more likely than males to have high or very high psychological distress (odds ratio 1.4; 95% CI 1.3–1.5). Among people with current asthma, the disparity in psychological distress between the sexes was even more pronounced. Females with current asthma were 1.8 times (95% CI 1.4–2.3) more likely to have high or very high psychological distress than males with current asthma (Figure 8.2). Furthermore, among females, those with current asthma were 2.2 times (95% CI 1.9–2.5) more likely to have high or very high psychological distress than those without asthma.
A Canadian study showed that, compared to the general population, the prevalence of both depressive disorders and anxiety disorders among adults with asthma was at least double the prevalence observed in the general population (Lavoie et al. 2006).
Recently, the World Mental Health Survey was conducted across 17 countries covering the Americas, Europe, the Middle East, Africa, Asia and New Zealand (Scott et al. 2007). Those who had ever received a doctor-diagnosis of asthma were 1.7 times (95% CI 1.4–2.1) more likely to have generalised anxiety than those without ‘ever asthma’, 1.7 times (95% CI 1.4–2.0) more likely to have agoraphobia (fear of open/public spaces) or panic disorder and 1.8 times (95% CI 1.4–2.3) more likely to have post-traumatic stress disorder.
8.2.2 Social domain
The social domain of HRQoL refers to the ability to perform roles and activities. This has most commonly been measured as time away from work or other usual activities.
Asthma accounts for a large proportion of days lost from work or study (Table 8.3).
In the ABS 2004–05 National Health Survey, the proportion of people with current asthma who had taken time off work or study in the previous 2 weeks because of any illness (16.6%) was higher than the proportion of people without asthma who had taken time off for any illness (10.7%; p<0.0001; see also Figure 8.3). The proportion of people with asthma who actually attributed their days off work or study to asthma was 1.2%.
Among participants in the 2004–05 NHS, more people with current asthma had days off work or school compared with people without current asthma (Figure 8.3). Almost twice as many people with current asthma had other days of reduced activity compared with those without current asthma (19.0% versus 10.0%) (p < 0.0001). It has been demonstrated that people with severe asthma tend to have greater absenteeism from work on account of their disease in comparison to those with mild-to-moderate asthma (ENFUMOSA Study Group 2003).
More females reported other days of reduced activity compared with males (Figure 8.4), although the disparity was more prominent among people with current asthma (21.3% of females versus 15.5% of males) compared with people without current asthma (11.1% of females versus 8.9% of males). A similar pattern was observed for days away from work or study.
Among those with asthma aged 5 years and over, 1.4% (95% CI 0.9–1.9%) had days off work or study and 1.9% (95% CI 1.3–2.5%) had other days of reduced activity because of their asthma in 2004–05 (data not shown).
Summary [back to top]
Asthma has a measurable impact on how people assess their overall health status. Asthma is associated with poorer self-assessed health, and a substantially higher proportion of days of reduced activity. Most of the impact of asthma is on physical functioning and on the ability to perform social roles. The effects of asthma can include sleep disturbances and tiredness, as well as reduced participation in the workforce and sporting and other leisure activities.
There is also an important association between depression and asthma. Australians with asthma report worse psychological health than those without asthma, and the difference is more pronounced in females and in older persons.
© Australian Institute of Health and Welfare 2008
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