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The prevalence of asthma and COPD in Italy: A practice-based study
Respiratory Medicine (2011) 105, 386e391 available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/rmed
The prevalence of asthma and COPD in Italy: A practice-based study Mario Cazzola a,b,*, Ermanno Puxeddu a, Germano Bettoncelli c, Lucia Novelli a, Andrea Segreti a, Claudio Cricelli c, Luigino Calzetta a a
Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy Pulmonary Rehabilitation Group, IRCCS San Raffaele Pisana, Rome, Italy c Health Search Institute, Italian College of General Practitioners, Florence, Italy b
Received 16 September 2010; accepted 30 September 2010 Available online 15 October 2010
KEYWORDS Asthma; COPD; Epidemiology; Administrative health database
Summary We conducted a population-based cross-sectional epidemiologic survey of asthma and COPD in an adult representative national sample using information obtained from the Health Search Database owned by the Italian College of General Practitioners. General Practitioners who had a list of patient population of 909,638 individuals (429,962 men and 479,676 women; man/woman ratio [M/WR]: 0.89) 14 years old at the end of December 2009 were selected to be representatives of the whole Italian population. Cases of asthma and COPD were identified on the basis of the ICD-9 codes. The total sample included 55,500 (6.10% of the entire population; 5.49% of men and 6.64% of women; M/WR: 0.74) subjects suffering from asthma and 25,762 (2.83% of the entire population; 3.51% of men and 2.23% of women; M/WR: 1.41) subjects suffering from COPD. The asthma/COPD ratio in general population was 2.16. The odds ratio (OR) was chosen because asthma and COPD had a prevalence less than 10%. The OR of developing asthma decreased with age both in men and women, but in the first group of age (15e34 years) it was higher in men vs. women (1.69 vs. 1.00) although it became lower than 1 from 35 years old and up in men and from 75 years old and up in women. On the contrary, the OR of developing COPD became higher than 1 from 55 years old and up both in men and in women and progressively increased with age (in the group 75e84 years, it was 6.16 in men and 4.07 in women, respectively). ª 2010 Elsevier Ltd. All rights reserved.
* Corresponding author. Cattedra di Malattie Respiratorie, Dipartimento di Medicina Interna, Universita ` di Roma Tor Vergata, Via Montpellier 1, IT-00133 Rome, Italy. E-mail address: [email protected] (M. Cazzola). 0954-6111/$ - see front matter ª 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.rmed.2010.09.022
The prevalence of asthma and COPD in Italy
387
Introduction
Analysis
Asthma and COPD are common chronic diseases of the airways that are mainly diagnosed and treated in general practice. The general practitioner (GP) is the provider of basic medical care and is the gateway to specialized care. Therefore, it is important that the GPs know the prevalence of different diseases in their practice. In Italy, national statistics on morbidity are based on selfreported information, and only few researchers have investigated whether some differences might arise when using data from Health Interview Surveys and from medical records.1 Unfortunately, the self-reported prevalence of asthma or COPD, when compared with GP registration, is associated with an overestimation in people who suffer from other respiratory conditions and with an underestimation in elderly persons living in a smoky environment who have fewer chronic diseases.2 The aim of this study was to epidemiologically investigate the prevalence and risk of asthma and COPD in Italy using medical records obtained from the Health Search Database (HSD) owned by the Italian College of General Practitioners (SIMG), which stores information on about 1.5% of the total Italian population served by general practitioners (GPs).
The study was carried out by a cross-sectional and observational field method. It permitted to describe the situation at the time of data collection, at the end of December 2009, and it allowed determining the prevalence of investigated outcomes. Furthermore, we evaluated the risk factor (RF) calculating the OR or RR. In order to investigate the association between variables, it was chosen to use OR instead of RR because the diseases of the study (asthma and COPD) have a relatively low prevalence that is less than 10%. Positive and negative OR values mean a co-relative positive and negative association between evaluated variables.5,6 This epidemiological study had a confidence level of 99.99% (setting the hypothesized % frequency of outcome factor in the population at 50% and confidence limit of 0.2%). The studied population was divided by several clusters: disease, age (15e34, 35e44, 45e54, 55e64, 65e74, 75e84 and older than 85 years old), and gender (male and female). In order to calculate statistical and epidemiological values, computer software GraphPad Prism (CA, USA) and OpenEpi (Dean AG, Sullivan KM, Soe MM. Open Source Epidemiologic Statistics for Public Health) were used.
Material and methods We conducted an adult population-based cross-sectional epidemiologic survey of asthma and COPD in a representative national sample using information obtained from the HSD. The software system used codes all the diagnostic records utilizing the International Classification of Diseases (9th revision: ICD-9).3 The participating GPs use the same software to record data during their daily practice, and they agree to send periodically complete, but anonymous, records of their patients to the HSD. A unique patient code links demographic and prescription information, clinical events and diagnoses, hospital admission, and cause of death. It is well known that before using any data resource, particularly one that is based on computer records, it is necessary to determine the quality and completeness of the available information. Therefore, data are subject to a range of quality checks. Any variations within agreed ranges are investigated and submitted to each participating GP. Physicians who fail to meet standard quality criteria are not considered for epidemiological studies.4 700 GPs, who had a list of patient population of 909,638 individuals (429,962 men and 479,676 women; man/woman ratio [M/WR]: 0.89) older than 14 years at the end of December 2009, were selected to be representatives of the whole Italian population and also because they ensured the required data quality. Since the study was a retrospective analysis of data already available in the HSD, and confidentiality of patients was in no way violated, local rules do not request approval by an ethics committee.
Ascertainment of COPD and asthma Cases of COPD were identified on the basis of the ICD-9 codes 491, 492, and 496, and those of asthma on the basis of the ICD9 code 493.
Results The total sample included 55,500 (6.10% of the entire population; 5.49% of men and 6.64% of women; M/WR:0.74) subjects suffering from asthma and 25,762 (2.83% of the entire population; 3.51% of men and 2.23% of women; M/ WR:1.41) subjects suffering from COPD. The asthma/COPD ratio in general population was 2.16 (Table 1). The prevalence of these diseases by age cluster is shown in Fig. 1. In asthma, it was higher in women in all age clusters except in the 15e34 group. In COPD, the prevalence was higher in men in all age clusters, with a marked difference between sexes after 64 years of age. The OR of developing asthma decreased with age both in men and women, but in the first group of age (15e34 years) it was higher in men vs. women (1.69 vs.1.00) although it became lower than 1 from 35 years old and up in men and from 75 years onwards in women. On the contrary, the OR of developing COPD became higher than 1 from 55 years old and up both in men and in women and progressively increased with age (in the group 75e84 years, it was 6.16 in men and 4.07 in women, respectively) (Fig. 2). In Fig. 3 we report the prevalence of smoking habit in the general Italian population using data recorded by the Italian Central Institute of Statistics (ISTAT). These data show that in asthmatic patients smoking does not play a role, whereas, as expected, in COPD there is an important correlation between smoking and disease.
Discussion The first important finding of our study is the documentation that the asthma/COPD ratio in our population was 2.16, with a prevalence of asthma and COPD of 6.10% and 2.83%, respectively. We must highlight that the prevalence of asthma in our study was very well in line with results
388 Table 1
M. Cazzola et al. Prevalence (%) and rates of asthma and COPD in population study by gender cluster. Prevalence (%)
Asthma COPD
Rates
Female
Male
Total
Male/female
Asthma/COPD female
Asthma/COPD male
Asthma/COPD total
6.64 2.23
5.49 3.51
6.10 2.83
0.83 1.57
2.98
1.56
2.16
from population studies of representative samples of the general population. This is not very common in register studies, as they normally results in underestimations. Therefore, we believe that this is a strength of our study and of the usefulness of the HSD. We cannot deny that there may have been misclassification when our GPs have used specific diagnostic categories. Despite the availability of consensus guideline diagnostic recommendations, diagnostic confusion between COPD and asthma appears common in primary care patients.7 The FinEsS-study assessed whether differences existed in prevalence of asthma, chronic bronchitis, and respiratory symptoms between three Baltic capitals, and examined the risk factor profiles for respiratory conditions.8 Prevalence of respiratory symptoms was higher in Tallinn than in Stockholm and Helsinki, while physician-diagnosed asthma was more common in Stockholm and Helsinki and the prevalence of physician-diagnosed chronic bronchitis was three times as high in Tallinn as in Helsinki or Stockholm. It is likely that these considerable differences in prevalence rates of physiciandiagnosed asthma and COPD were due to substantial difference in diagnostic practices between the three countries, while the differences between the capitals in true prevalence of disease was small. In general, COPD is underestimated by GPs. In a population-based study in which COPD was diagnosed based on the assessment of lung function by means of spirometry, the so called Burden Of Obstructive Lung Disease (BOLD) study, prevalences between 8.2 and 19.1% in adults 40 years of age or older were found.9 In primary care, much lower estimates of the prevalence of physician-diagnosed COPD have been
reported (between 1.5 and 3%).10e12 However, we must stress that the BOLD study included also mild COPD (which comprise approximately a half of the COPD-cases) with the diagnosis based only on the FEV1/FVC ratio < 0.79 and they could have a normal FEV1, so it is not surprising that all these mild COPD cases not are identified by the health care system. On the other hand, some studies found an overdiagnosis of asthma in primary health care.13,14 In particular, Aaron and colleagues recently found that about one-third of obese and nonobese individuals with physician-diagnosed asthma had no evidence of asthma when their medications were tapered and when they were evaluated with serial assessments of symptoms, lung function and bronchial challenge tests.15 We recognize that GPs are faced with an array of alternative codes for the same or similar conditions. In effect, practicing physicians have little faith in the accuracy of the ICD-9 diagnoses entered for prescription purposes and this can question the real value of diagnoses in the HSD, including that of COPD and asthma. It is plausible that misdiagnosis, including possible gender bias, could be reduced by the appropriate use of objective laboratory studies. Unfortunately, previously, it was shown that Italian GPs make little use of spirometry in their investigation of chronic respiratory symptoms.16 In the majority of our patients, the diagnosis of asthma or COPD was mainly clinical and this can be interpreted as a severe limitation. In 2004, Viegi and colleagues17 analyzed data from two prospective studies (4353 subjects who had acceptable FVC test results) carried out in Italy, in the rural area of Po River delta from 1988 to 1991 and in the urban area of Pisa from 1991 to 1993. Prevalence rates of asthma,
Fig. 1 Cases of asthma and COPD in the studied Italian population. Points shown represent the prevalence (%) of asthma and COPD by age and gender clusters.
The prevalence of asthma and COPD in Italy
389
Fig. 2 Risk factors of asthma and COPD. Points shown represent odds ratios and 95% confidence limits of associations between risk of asthma and COPD and age and gender. Values >1 indicate a positive association and values <1 indicate negative association, DP < 0.05 vs. non-exposed population.
chronic bronchitis, and emphysema were 5.3%, 1.5%, and 1.2% in the Po delta, and 6.5%, 2.5%, and 3.6% in Pisa. For both genders, the frequency of isolated asthma decreased with age, while that of isolated airflow obstruction, chronic bronchitis-emphysema, and the combination of asthma and chronic bronchitis-emphysema increased. It is difficult to compare the results of that study and our results, since there are considerable differences in the methods used and the study populations included. In particular, our analysis was restricted to those patients who consulted their GPs. Therefore, the conclusions of our study are probably not valid for the healthiest people: those who did not consult their GPs at all. Nonetheless, our research, using a larger population with a different approach, confirmed that the prevalence of asthma was higher than that of COPD and, moreover, age was a strong and positive risk factor of COPD, whereas in asthma the correlation between disease and age was weakly negative. Similarities in the conclusions of our study and those of Viegi and colleagues17 are important considering that it has been highlighted that distinction between COPD and asthma may be relatively easy in patients with severe disease or in
older patients, but in many cases it is not so clear as clinical signs and symptoms show overlap. This is particularly the case in family practice, where the diagnostic process is primarily based on symptoms and signs presented by the patient.18 In any case, it must be mentioned that only 25e50% of asthma or COPD patients are known to their doctor.19 In fact, it seems that the majority of patients with a decreased FEV1 do not complain of any bronchial symptoms.20 Poor perception of dyspnoea is a probable cause of underpresentation by patients, so neither the physician nor the patient is to blame for the underdiagnosis of asthma or COPD in the general population.10 Our data confirm that young adults are at highest risk of having a diagnosis of asthma. In the current study, the prevalence was highest in the age group of 15e34 years old (physician-diagnosed asthma 7.19%) and declined progressively to become 4.12 in the cluster of age >85 years old. However, the decrease in prevalence was progressive in men, but women showed an increase in prevalence up to the cluster of age 45e54 years old and soon after a progressive decrease, although the prevalence remained always higher in women than in men. This last finding contrasts with
Fig. 3 Prevalence (%, A) and correlation (rate, B and C) of smoking habit and asthma or COPD by gender clusters. B and C: values >0 indicate a positive correlation and values <0 indicate negative correlation. Smoking habit data of general population (A) were obtained from the Italian Statistical Yearbook 2009 of Italian Central Institute of Statistic (ISTAT), available at http://www.istat.it.
390 a British documentation that in people older than 70 years, current asthma was more prevalent in men than women (5.1% compared to 1.8%).21 Also a cross-sectional French study documented that in men, the prevalence rate was higher that in women (7.3% for cumulative asthma and 2.8% for current asthma vs. 5.2% and 2.2%, respectively). In any case, as in our study, the rates were lower at advanced ages (>85 years) for both men and women.22 Consistent with the international epidemiology of COPD,9 a progressive rise of prevalence with age in both sexes until the age of 84 years was observed. The prevalence was higher in men than in women. For those aged 75 years and older, the prevalence was 14.15% for men and 6.61% for women. Report from the Obstructive Lung Disease in Northern Sweden (OLIN) Studies confirms that increasing age, together with smoking, is the dominating risk factor for COPD.23 In our study, male gender was a risk factor of asthma only in young people, being the ORs in men always lower than 1 from 35 years old and up. This finding contrasts with the documentation in the “Pollution Atmospherique et Affections Respiratoires” (PAARC) study that, from aged 50 yrs upwards rates in men increased.24 On the contrary, in our study female gender was a significant risk factor only in the age group 45e54 years, with an OR that was 1.11. From 75 years old and up, the ORs were lower than 1 also in women. Our results differ from those reported by Osman and colleagues25 documenting a higher prevalence of asthma in women from 15 years old and up. The timing of the gender reversal in asthma prevalence has generally been reported to occur between 10 and 20 years of age in most studies, with exceptions locating the switch beyond 20 years.26 However they fit with other Italian reports. The prevalence of an “episode of asthma” (defined as a selfreported attack of asthma or treatment for asthma) and of “current asthma” (defined as a self-reported attack of asthma, treatment for asthma or wheezing other than due to a cold with dyspnoea in the last 12 months) was 3.47% (3.74% in men and 3.14% in women) and 5.01% (5.07% in men and 4.90% in women), respectively, in randomly selected subjects, aged 20e44 years, living in three areas of northern Italy: Turin, Pavia, and Verona.27 Interestingly, no differences were found on the basis of age and sex. In a French survey, asthma was inversely correlated to age (higher prevalence in the youngest) but was not related to sex.28 Nonetheless, it is important to highlight that an analysis based on a total of 9,486,173 hospital records in Canada for a 3-year period, including 204,304 asthma patients and 288,977 asthma-related records, showed that the incidence ratio for women vs. men for asthma hospitalization reached 2.8 for individuals 25e34 years of age, decreased gradually with increasing age, and then approached unity for those aged 80 years or more.29 Contrary to that observed by others who reported that men would have a higher risk of COPD than women in the younger age groups (45e49 years, 50e54 years) and women would show a higher risk in the older age groups up to the 75e79 years,30 in our population the risk of COPD was always higher in men than in women regardless of age. In conclusion, our findings show that the prevalence of asthma is higher than that of COPD in an adult Italian general population with higher prevalence of asthma in women and higher prevalence of COPD in men. It is important to stress
M. Cazzola et al. that this information comes from an administrative health database. We believe databases provide a valuable method for identifying sex differences in the epidemiology of asthma and COPD, because they provide large sample sizes, have strong statistical power, are relatively inexpensive studies to conduct, and can link information on diagnosis, and treatment. An administrative health database may represent the ‘real world’ more accurately and characterize sex differences more fully than do other data sources.
Conflict of interest statement The authors declare that they have no competing interests.
References 1. Cricelli C, Mazzaglia G, Samani F, Marchi M, Sabatini A, Nardi R, et al. Prevalence estimates for chronic diseases in Italy: exploring the differences between self-report and primary care databases. J Public Health Med 2003;25:254e7. 2. Mohangoo AD, van der Linden MW, Schellevis FG, Raat H. Prevalence estimates of asthma or COPD from a health interview survey and from general practitioner registration: what’s the difference? Eur J Public Health 2006;16:101e5. 3. World Health Organisation. International classification of diseases, Manual of the international statistical classification of diseases: injuries and causes of deaths. Geneva: WHO; 1977 [9th revision]. 4. Lawrenson R, Williams T, Farmer R. Clinical information for research: the use of general practice databases. J Public Health Med 1999;21:299e304. 5. Schmidt CO, Kohlmann T. When to use the Odds Ratio or the relative risk? Int J Public Health 2008;53:165e7. 6. Motulsky H. Intuitive biostatistics. New York, Oxford: Oxford University Press; 1995. 7. Breyer MK, Spruit MA, Celis AP, Rutten EP, Janssen PP, Wouters EF. Highly elevated C-reactive protein levels in obese patients with COPD: a fat chance? Clin Nutr 2009;28:642e7. 8. Pallasaho P, Lundba ¨ck B, Meren M, Kiviloog J, Loit HM, Larsson K, et al. Prevalence and risk factors for asthma and chronic bronchitis in the capitals Helsinki, Stockholm, and Tallinn. Respir Med 2002;96:759e69. 9. Buist AS, McBurnie MA, Vollmer WM, Gillespie S, Burney P, Mannino DM, et al. International variation in the prevalence of COPD (the BOLD Study): a population-based prevalence study. Lancet 2007;370:741e50. 10. White P. Prevalence of COPD in primary care: no room for complacency. Fam Pract 2009;26:1e2. 11. Chapman KR. Chronic obstructive pulmonary disease: are women more susceptible than men? Clin Chest Med 2004;25: 331e41. 12. Soriano JB, Maier WC, Egger P, Visick G, Thakrar B, Sykes J, et al. Recent trends in physician diagnosed COPD in women and men in the UK. Thorax 2000;55:789e94. 13. Marklund B, Tunsa ¨ter A, Bengtsson C. How often is the diagnosis bronchial asthma correct? Fam Pract 1999;16:112e6. 14. Tinkelman DG, Price DB, Nordyke RJ, Halbert RJ. Misdiagnosis of COPD and asthma in primary care patients 40 years of age and over. J Asthma 2006;43:75e80. 15. Aaron SD, Vandemheen KL, Boulet LP, McIvor RA, Fitzgerald JM, Hernandez P, et al. Overdiagnosis of asthma in obese and nonobese adults. CMAJ 2008;179:1121e31. 16. Lusuardi M, De Benedetto F, Paggiaro P, Sanguinetti CM, Brazzola G, Ferri P, et al. A randomized controlled trial on office spirometry in asthma and COPD in standard general
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practice: data from spirometry in asthma and COPD: a comparative evaluation Italian study. Chest 2006;129: 844e52. Viegi G, Matteelli G, Angino A, Scognamiglio A, Baldacci S, Soriano JB, et al. The proportional Venn diagram of obstructive lung disease in the Italian general population. Chest 2004;126: 1093e101. Albers M, Schermer T, Molema J, Kloek C, Akkermans R, Heijdra Y, et al. Do family physicians’ records fit guideline diagnosed COPD? Fam Pract 2009;26:81e7. van Schayck CP, Chavannes NH. Detection of asthma and chronic obstructive pulmonary disease in primary care. Eur Respir J 2003;39(Suppl.):16se22s. Tirimanna PRS, van Schayck CP, den Otter JJ, et al. Prevalence of asthma and COPD in general practice in 1992: has it changed since 1977? Br J Gen Pract 1996;46:277e81. Burr ML, Charles TJ, Roy K, Seaton A. Asthma in the elderly: an epidemiological survey. Br Med J 1979;1:1041e4. Nejjari C, Tessier JF, Letenneur L, Dartigues JF, BarbergerGateau P, Salamon R. Prevalence of self-reported asthma symptoms in a French elderly sample. Respir Med 1996;90:401e8. Lindberg A, Bjerg-Ba ¨cklund A, Ro ¨nmark E, Larsson LG, Lundba ¨ck B. Prevalence and underdiagnosis of COPD by disease severity and the attributable fraction of smoking. Report from
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the obstructive lung disease in Northern Sweden studies. Respir Med 2006;100:264e72. Kauffmann F, Becklake MR. Maladies obstructives pulmonaires: un paradigme de la complexite ´ des diffe ´rences de sante ´ entre hommes et femmes. In: La sante´ des femmes. Paris: Medecine et Sciences; 1996. p. 209e33. Osman M, Hansell AL, Simpson CR, Hollowell J, Helms PJ. Gender-specific presentations for asthma, allergic rhinitis and eczema in primary care. Prim Care Respir J 2007;16:28e35. Zannolli R, Morgese G. Does puberty interfere with asthma? Med Hypotheses 1997;48:27e32. Marinoni A. Prevalence of asthma and asthma symptoms in a general population sample from northern Italy. Allergy 1995; 50:755e9. Neukirch F, Pin I, Knani J, Henry C, Pison C, Liard R, et al. Prevalence of asthma and asthma-like symptoms in three French cities. Respir Med 1995;89:685e92. Chen Y, Stewart P, Johansen H, McRae L, Taylor G. Sex difference in hospitalization due to asthma in relation to age. J Clin Epidemiol 2003;56:180e7. Camp PG, Chaudhry M, Platt H, Roch M, Road J, Sin D, et al. The sex factor: epidemiology and management of chronic obstructive pulmonary disease in British Columbia. Can Respir J 2008;15:417e22.
journal homepage: www.elsevier.com/locate/rmed
The prevalence of asthma and COPD in Italy: A practice-based study Mario Cazzola a,b,*, Ermanno Puxeddu a, Germano Bettoncelli c, Lucia Novelli a, Andrea Segreti a, Claudio Cricelli c, Luigino Calzetta a a
Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy Pulmonary Rehabilitation Group, IRCCS San Raffaele Pisana, Rome, Italy c Health Search Institute, Italian College of General Practitioners, Florence, Italy b
Received 16 September 2010; accepted 30 September 2010 Available online 15 October 2010
KEYWORDS Asthma; COPD; Epidemiology; Administrative health database
Summary We conducted a population-based cross-sectional epidemiologic survey of asthma and COPD in an adult representative national sample using information obtained from the Health Search Database owned by the Italian College of General Practitioners. General Practitioners who had a list of patient population of 909,638 individuals (429,962 men and 479,676 women; man/woman ratio [M/WR]: 0.89) 14 years old at the end of December 2009 were selected to be representatives of the whole Italian population. Cases of asthma and COPD were identified on the basis of the ICD-9 codes. The total sample included 55,500 (6.10% of the entire population; 5.49% of men and 6.64% of women; M/WR: 0.74) subjects suffering from asthma and 25,762 (2.83% of the entire population; 3.51% of men and 2.23% of women; M/WR: 1.41) subjects suffering from COPD. The asthma/COPD ratio in general population was 2.16. The odds ratio (OR) was chosen because asthma and COPD had a prevalence less than 10%. The OR of developing asthma decreased with age both in men and women, but in the first group of age (15e34 years) it was higher in men vs. women (1.69 vs. 1.00) although it became lower than 1 from 35 years old and up in men and from 75 years old and up in women. On the contrary, the OR of developing COPD became higher than 1 from 55 years old and up both in men and in women and progressively increased with age (in the group 75e84 years, it was 6.16 in men and 4.07 in women, respectively). ª 2010 Elsevier Ltd. All rights reserved.
* Corresponding author. Cattedra di Malattie Respiratorie, Dipartimento di Medicina Interna, Universita ` di Roma Tor Vergata, Via Montpellier 1, IT-00133 Rome, Italy. E-mail address: [email protected] (M. Cazzola). 0954-6111/$ - see front matter ª 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.rmed.2010.09.022
The prevalence of asthma and COPD in Italy
387
Introduction
Analysis
Asthma and COPD are common chronic diseases of the airways that are mainly diagnosed and treated in general practice. The general practitioner (GP) is the provider of basic medical care and is the gateway to specialized care. Therefore, it is important that the GPs know the prevalence of different diseases in their practice. In Italy, national statistics on morbidity are based on selfreported information, and only few researchers have investigated whether some differences might arise when using data from Health Interview Surveys and from medical records.1 Unfortunately, the self-reported prevalence of asthma or COPD, when compared with GP registration, is associated with an overestimation in people who suffer from other respiratory conditions and with an underestimation in elderly persons living in a smoky environment who have fewer chronic diseases.2 The aim of this study was to epidemiologically investigate the prevalence and risk of asthma and COPD in Italy using medical records obtained from the Health Search Database (HSD) owned by the Italian College of General Practitioners (SIMG), which stores information on about 1.5% of the total Italian population served by general practitioners (GPs).
The study was carried out by a cross-sectional and observational field method. It permitted to describe the situation at the time of data collection, at the end of December 2009, and it allowed determining the prevalence of investigated outcomes. Furthermore, we evaluated the risk factor (RF) calculating the OR or RR. In order to investigate the association between variables, it was chosen to use OR instead of RR because the diseases of the study (asthma and COPD) have a relatively low prevalence that is less than 10%. Positive and negative OR values mean a co-relative positive and negative association between evaluated variables.5,6 This epidemiological study had a confidence level of 99.99% (setting the hypothesized % frequency of outcome factor in the population at 50% and confidence limit of 0.2%). The studied population was divided by several clusters: disease, age (15e34, 35e44, 45e54, 55e64, 65e74, 75e84 and older than 85 years old), and gender (male and female). In order to calculate statistical and epidemiological values, computer software GraphPad Prism (CA, USA) and OpenEpi (Dean AG, Sullivan KM, Soe MM. Open Source Epidemiologic Statistics for Public Health) were used.
Material and methods We conducted an adult population-based cross-sectional epidemiologic survey of asthma and COPD in a representative national sample using information obtained from the HSD. The software system used codes all the diagnostic records utilizing the International Classification of Diseases (9th revision: ICD-9).3 The participating GPs use the same software to record data during their daily practice, and they agree to send periodically complete, but anonymous, records of their patients to the HSD. A unique patient code links demographic and prescription information, clinical events and diagnoses, hospital admission, and cause of death. It is well known that before using any data resource, particularly one that is based on computer records, it is necessary to determine the quality and completeness of the available information. Therefore, data are subject to a range of quality checks. Any variations within agreed ranges are investigated and submitted to each participating GP. Physicians who fail to meet standard quality criteria are not considered for epidemiological studies.4 700 GPs, who had a list of patient population of 909,638 individuals (429,962 men and 479,676 women; man/woman ratio [M/WR]: 0.89) older than 14 years at the end of December 2009, were selected to be representatives of the whole Italian population and also because they ensured the required data quality. Since the study was a retrospective analysis of data already available in the HSD, and confidentiality of patients was in no way violated, local rules do not request approval by an ethics committee.
Ascertainment of COPD and asthma Cases of COPD were identified on the basis of the ICD-9 codes 491, 492, and 496, and those of asthma on the basis of the ICD9 code 493.
Results The total sample included 55,500 (6.10% of the entire population; 5.49% of men and 6.64% of women; M/WR:0.74) subjects suffering from asthma and 25,762 (2.83% of the entire population; 3.51% of men and 2.23% of women; M/ WR:1.41) subjects suffering from COPD. The asthma/COPD ratio in general population was 2.16 (Table 1). The prevalence of these diseases by age cluster is shown in Fig. 1. In asthma, it was higher in women in all age clusters except in the 15e34 group. In COPD, the prevalence was higher in men in all age clusters, with a marked difference between sexes after 64 years of age. The OR of developing asthma decreased with age both in men and women, but in the first group of age (15e34 years) it was higher in men vs. women (1.69 vs.1.00) although it became lower than 1 from 35 years old and up in men and from 75 years onwards in women. On the contrary, the OR of developing COPD became higher than 1 from 55 years old and up both in men and in women and progressively increased with age (in the group 75e84 years, it was 6.16 in men and 4.07 in women, respectively) (Fig. 2). In Fig. 3 we report the prevalence of smoking habit in the general Italian population using data recorded by the Italian Central Institute of Statistics (ISTAT). These data show that in asthmatic patients smoking does not play a role, whereas, as expected, in COPD there is an important correlation between smoking and disease.
Discussion The first important finding of our study is the documentation that the asthma/COPD ratio in our population was 2.16, with a prevalence of asthma and COPD of 6.10% and 2.83%, respectively. We must highlight that the prevalence of asthma in our study was very well in line with results
388 Table 1
M. Cazzola et al. Prevalence (%) and rates of asthma and COPD in population study by gender cluster. Prevalence (%)
Asthma COPD
Rates
Female
Male
Total
Male/female
Asthma/COPD female
Asthma/COPD male
Asthma/COPD total
6.64 2.23
5.49 3.51
6.10 2.83
0.83 1.57
2.98
1.56
2.16
from population studies of representative samples of the general population. This is not very common in register studies, as they normally results in underestimations. Therefore, we believe that this is a strength of our study and of the usefulness of the HSD. We cannot deny that there may have been misclassification when our GPs have used specific diagnostic categories. Despite the availability of consensus guideline diagnostic recommendations, diagnostic confusion between COPD and asthma appears common in primary care patients.7 The FinEsS-study assessed whether differences existed in prevalence of asthma, chronic bronchitis, and respiratory symptoms between three Baltic capitals, and examined the risk factor profiles for respiratory conditions.8 Prevalence of respiratory symptoms was higher in Tallinn than in Stockholm and Helsinki, while physician-diagnosed asthma was more common in Stockholm and Helsinki and the prevalence of physician-diagnosed chronic bronchitis was three times as high in Tallinn as in Helsinki or Stockholm. It is likely that these considerable differences in prevalence rates of physiciandiagnosed asthma and COPD were due to substantial difference in diagnostic practices between the three countries, while the differences between the capitals in true prevalence of disease was small. In general, COPD is underestimated by GPs. In a population-based study in which COPD was diagnosed based on the assessment of lung function by means of spirometry, the so called Burden Of Obstructive Lung Disease (BOLD) study, prevalences between 8.2 and 19.1% in adults 40 years of age or older were found.9 In primary care, much lower estimates of the prevalence of physician-diagnosed COPD have been
reported (between 1.5 and 3%).10e12 However, we must stress that the BOLD study included also mild COPD (which comprise approximately a half of the COPD-cases) with the diagnosis based only on the FEV1/FVC ratio < 0.79 and they could have a normal FEV1, so it is not surprising that all these mild COPD cases not are identified by the health care system. On the other hand, some studies found an overdiagnosis of asthma in primary health care.13,14 In particular, Aaron and colleagues recently found that about one-third of obese and nonobese individuals with physician-diagnosed asthma had no evidence of asthma when their medications were tapered and when they were evaluated with serial assessments of symptoms, lung function and bronchial challenge tests.15 We recognize that GPs are faced with an array of alternative codes for the same or similar conditions. In effect, practicing physicians have little faith in the accuracy of the ICD-9 diagnoses entered for prescription purposes and this can question the real value of diagnoses in the HSD, including that of COPD and asthma. It is plausible that misdiagnosis, including possible gender bias, could be reduced by the appropriate use of objective laboratory studies. Unfortunately, previously, it was shown that Italian GPs make little use of spirometry in their investigation of chronic respiratory symptoms.16 In the majority of our patients, the diagnosis of asthma or COPD was mainly clinical and this can be interpreted as a severe limitation. In 2004, Viegi and colleagues17 analyzed data from two prospective studies (4353 subjects who had acceptable FVC test results) carried out in Italy, in the rural area of Po River delta from 1988 to 1991 and in the urban area of Pisa from 1991 to 1993. Prevalence rates of asthma,
Fig. 1 Cases of asthma and COPD in the studied Italian population. Points shown represent the prevalence (%) of asthma and COPD by age and gender clusters.
The prevalence of asthma and COPD in Italy
389
Fig. 2 Risk factors of asthma and COPD. Points shown represent odds ratios and 95% confidence limits of associations between risk of asthma and COPD and age and gender. Values >1 indicate a positive association and values <1 indicate negative association, DP < 0.05 vs. non-exposed population.
chronic bronchitis, and emphysema were 5.3%, 1.5%, and 1.2% in the Po delta, and 6.5%, 2.5%, and 3.6% in Pisa. For both genders, the frequency of isolated asthma decreased with age, while that of isolated airflow obstruction, chronic bronchitis-emphysema, and the combination of asthma and chronic bronchitis-emphysema increased. It is difficult to compare the results of that study and our results, since there are considerable differences in the methods used and the study populations included. In particular, our analysis was restricted to those patients who consulted their GPs. Therefore, the conclusions of our study are probably not valid for the healthiest people: those who did not consult their GPs at all. Nonetheless, our research, using a larger population with a different approach, confirmed that the prevalence of asthma was higher than that of COPD and, moreover, age was a strong and positive risk factor of COPD, whereas in asthma the correlation between disease and age was weakly negative. Similarities in the conclusions of our study and those of Viegi and colleagues17 are important considering that it has been highlighted that distinction between COPD and asthma may be relatively easy in patients with severe disease or in
older patients, but in many cases it is not so clear as clinical signs and symptoms show overlap. This is particularly the case in family practice, where the diagnostic process is primarily based on symptoms and signs presented by the patient.18 In any case, it must be mentioned that only 25e50% of asthma or COPD patients are known to their doctor.19 In fact, it seems that the majority of patients with a decreased FEV1 do not complain of any bronchial symptoms.20 Poor perception of dyspnoea is a probable cause of underpresentation by patients, so neither the physician nor the patient is to blame for the underdiagnosis of asthma or COPD in the general population.10 Our data confirm that young adults are at highest risk of having a diagnosis of asthma. In the current study, the prevalence was highest in the age group of 15e34 years old (physician-diagnosed asthma 7.19%) and declined progressively to become 4.12 in the cluster of age >85 years old. However, the decrease in prevalence was progressive in men, but women showed an increase in prevalence up to the cluster of age 45e54 years old and soon after a progressive decrease, although the prevalence remained always higher in women than in men. This last finding contrasts with
Fig. 3 Prevalence (%, A) and correlation (rate, B and C) of smoking habit and asthma or COPD by gender clusters. B and C: values >0 indicate a positive correlation and values <0 indicate negative correlation. Smoking habit data of general population (A) were obtained from the Italian Statistical Yearbook 2009 of Italian Central Institute of Statistic (ISTAT), available at http://www.istat.it.
390 a British documentation that in people older than 70 years, current asthma was more prevalent in men than women (5.1% compared to 1.8%).21 Also a cross-sectional French study documented that in men, the prevalence rate was higher that in women (7.3% for cumulative asthma and 2.8% for current asthma vs. 5.2% and 2.2%, respectively). In any case, as in our study, the rates were lower at advanced ages (>85 years) for both men and women.22 Consistent with the international epidemiology of COPD,9 a progressive rise of prevalence with age in both sexes until the age of 84 years was observed. The prevalence was higher in men than in women. For those aged 75 years and older, the prevalence was 14.15% for men and 6.61% for women. Report from the Obstructive Lung Disease in Northern Sweden (OLIN) Studies confirms that increasing age, together with smoking, is the dominating risk factor for COPD.23 In our study, male gender was a risk factor of asthma only in young people, being the ORs in men always lower than 1 from 35 years old and up. This finding contrasts with the documentation in the “Pollution Atmospherique et Affections Respiratoires” (PAARC) study that, from aged 50 yrs upwards rates in men increased.24 On the contrary, in our study female gender was a significant risk factor only in the age group 45e54 years, with an OR that was 1.11. From 75 years old and up, the ORs were lower than 1 also in women. Our results differ from those reported by Osman and colleagues25 documenting a higher prevalence of asthma in women from 15 years old and up. The timing of the gender reversal in asthma prevalence has generally been reported to occur between 10 and 20 years of age in most studies, with exceptions locating the switch beyond 20 years.26 However they fit with other Italian reports. The prevalence of an “episode of asthma” (defined as a selfreported attack of asthma or treatment for asthma) and of “current asthma” (defined as a self-reported attack of asthma, treatment for asthma or wheezing other than due to a cold with dyspnoea in the last 12 months) was 3.47% (3.74% in men and 3.14% in women) and 5.01% (5.07% in men and 4.90% in women), respectively, in randomly selected subjects, aged 20e44 years, living in three areas of northern Italy: Turin, Pavia, and Verona.27 Interestingly, no differences were found on the basis of age and sex. In a French survey, asthma was inversely correlated to age (higher prevalence in the youngest) but was not related to sex.28 Nonetheless, it is important to highlight that an analysis based on a total of 9,486,173 hospital records in Canada for a 3-year period, including 204,304 asthma patients and 288,977 asthma-related records, showed that the incidence ratio for women vs. men for asthma hospitalization reached 2.8 for individuals 25e34 years of age, decreased gradually with increasing age, and then approached unity for those aged 80 years or more.29 Contrary to that observed by others who reported that men would have a higher risk of COPD than women in the younger age groups (45e49 years, 50e54 years) and women would show a higher risk in the older age groups up to the 75e79 years,30 in our population the risk of COPD was always higher in men than in women regardless of age. In conclusion, our findings show that the prevalence of asthma is higher than that of COPD in an adult Italian general population with higher prevalence of asthma in women and higher prevalence of COPD in men. It is important to stress
M. Cazzola et al. that this information comes from an administrative health database. We believe databases provide a valuable method for identifying sex differences in the epidemiology of asthma and COPD, because they provide large sample sizes, have strong statistical power, are relatively inexpensive studies to conduct, and can link information on diagnosis, and treatment. An administrative health database may represent the ‘real world’ more accurately and characterize sex differences more fully than do other data sources.
Conflict of interest statement The authors declare that they have no competing interests.
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