The impact of asthma, chronic bronchitis and allergic rhinitis on all-cause hospitalizations and limitations in daily activities: a population-based observational study

Our data show that the risk of hospitalization and the number of days with impaired activities due to any health problems (apart from accidents and injuries) are impressively higher among adults with asthma, chronic bronchitis or allergic rhinitis, as compared to unaffected individuals from the general population in Italy. This result is in agreement with the findings in other studies, which show that respiratory symptoms are among the major causes of consultation at primary health care centres in different countries [24], and that these diseases impair work performance, social life and physical quality of life [25-27].

In each age class, the heaviest burden is associated with the coexistence of asthma and chronic bronchitis. In particular, the risk of all-cause hospitalization peaks among the 45–64 year-old subjects with both these conditions, whereas this risk is not so much higher than the figures observed among the individuals with the other respiratory conditions in the 20–44 age class. A possible explanation for this could be that the presence of chronic bronchitis may be an early expression of COPD in the older age group [28], whereas it may be an expression of post nasal drip among the individuals aged 20–44 [29].

Among the 45–64 year-old subjects, those reporting asthma-like symptoms/dyspnoea/other nasal problems show a heavy burden. This result could be explained by the age-related increase in the incidence of pneumonia, lung cancer, COPD or other diseases that cause dyspnoea or respiratory symptoms, which often require ED visits or hospital admissions.

In our study, breathing problems account for less than 50% of all-cause hospitalizations and limitations in daily activities. This is not surprising because Druss and colleagues [30] reported that about one fourth of the costs due to five chronic conditions (mood disorders, diabetes, heart disease, asthma and hypertension) in the United States were incurred in treating the conditions themselves, whereas the remaining costs were due to coexisting illnesses.

The contribution of breathing problems to the total burden varies according to the respiratory condition, even if the results pertaining to the 45–64 age class should be interpreted with caution because of the large confidence intervals, which is due to the smaller sample size of that group, as compared with the dimension of the 20–44 age class. In particular, the highest weight of breathing problems is found among the subjects with coexisting asthma and chronic bronchitis, which suggests that the burden for these patients is mainly caused by the disease. This result indirectly confirms that chronic bronchitis is associated with both a more severe form of the disease and poor control of symptoms in asthmatic subjects [7,8], or it may be an expression of the coexistence of asthma and COPD [9,10]. Accordingly, poor control of symptoms and coexisting chronic bronchitis were both associated with increased disease-related costs in European adults with asthma [12]. On the contrary, the contribution of breathing problems is particularly low among the subjects with allergic rhinitis only, whereas it is at an intermediate level among those with asthma or chronic bronchitis only, which suggests a progressive increase in the level of impairment due to these respiratory diseases.

Breathing problems have the lowest weight in determining all-cause hospitalizations and limitations in daily activities for the subjects with asthma-like symptoms/dyspnoea/other nasal problems. Different factors may contribute to explain this finding. Smoking is associated with respiratory symptoms and it is strongly associated with cardiac and cerebrovascular diseases, and with diabetic complications. Dyspnoea and non-specific respiratory symptoms may be attributable to other illnesses, such as heart failure, essential hypertension, anaemia, electrolyte disorders or gastroesophageal reflux. Moreover, in the case of comorbidities such as diabetes, anaemia, hypertension or tachycardia, the decision to admit a patient can be based not only on factors that are directly related to the respiratory disease, but also on the difficulty in managing an outpatient. In fact, these patients are likely to require more health services and more complex health management strategies.

Females aged 20–44 report a heavier burden as compared to males in the same age class, regardless of their disease status. In fact, females are probably more concerned about their health than males [31], as previously found among young adults with asthma in Italy [32]. On the contrary, the risk of all-cause hospitalization is lower among females aged 45–64, in accordance with official Italian statistics for the same period [33]. A heavier burden is reported by subjects with a low occupational status (i.e. blue collars and unemployed/retired individuals), in accordance with previous results for adult asthma in Italy [32]. This could be due to factors that affect health and are more frequent in lower social classes, such as residential and workplace pollutant exposures [34], or it could reflect a cumulative life course disadvantage [35]. Self-reported high levels of outdoor air pollution are associated with an increased risk of all-cause hospitalization among the subjects aged 45–64, which suggests that the exposure to air pollution has a long-term effect on health [36,37]. Finally, the pattern of association between smoking habits and the total burden could be due to the “healthy smoker effect” bias, since the subjects with the most severe underlying disease are the least likely to smoke [38].

The main strength of the present analysis is that the data were collected through a highly standardized protocol [17], which ensures the comparability of the information among the centres. Moreover, the prevalence rates are based on self-reported symptoms, which were measured through an international validated questionnaire [18], and are less influenced by diagnostic procedures. In addition, the data were collected from patients who had been identified in the general population, rather than from clinically selected groups, which should guarantee that the studied sample encompasses a wide spectrum of respiratory conditions. Finally, a potential measurement error [39] could have influenced our estimates of the burden only to a minor extent, because our study did not involve elderly patients and the recall period considered in the questionnaire (three months) was short.

A few caveats should be taken into account when interpreting our results. Only four centres participating in GEIRD collected the information on the subjects aged 45–64 and so there could be a potential limitation in the generalizability of the results. Moreover, the participation rate was quite low (53.0%) among young adults, as observed in other epidemiological studies over the past decades [40], and this may have biased our estimates for this age class. However, it has been suggested that decreasing participation rates are not likely to have a substantial influence on the point estimates of measures of interest [40]. Finally, it was not possible to directly evaluate the impact of comorbidities on the total burden because questions on coexisting diseases had not been included in the screening questionnaire, in order to minimize its length and therefore increase the response rate [18]. In addition, the screening questionnaire does not allow to compute separate estimates of the risk of having at least one ED visit and of the risk of having at least one hospital admission in the past three months. Therefore, the possible overestimation of hospital services utilization cannot be detected through the comparison with ED visit rates and hospital in-patient admission rates from other sources. However, participation bias could have inflated our estimates of the hospitalization risk to some extent.