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PEDOT-7370; No. of Pages 4 International Journal of Pediatric Otorhinolaryngology xxx (2014) xxx–xxx

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International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl

Cholesteatoma in Danish children – A national study of changes in the incidence rate over 34 years Bjarki Ditlev Djurhuus a,*, Axel Skytthe b, Kaare Christensen b, Christian Emil Faber a a b

Department of ENT Head & Neck Surgery, Odense University Hospital, Odense, Denmark Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark

A R T I C L E I N F O

A B S T R A C T

Article history: Received 15 August 2014 Received in revised form 14 November 2014 Accepted 18 November 2014 Available online xxx

Objective: To describe temporal trends in the incidence rate of surgically treated middle ear cholesteatoma in Danish children from 1977 to 2010. Methods: Data on surgically treated middle ear cholesteatoma was drawn from the Danish National Patient Register. A change in incidence rate over time was examined using Poisson regression analysis, while the cumulative incidence proportion was estimated using life-tables. Results: A total of 5850 cases of surgically treated middle ear cholesteatoma distributed among 3874 children aged 0–15 years were identified. From 1977 to 2002 the age-standardized incidence rates for first-time surgically treated middle ear cholesteatoma increased from 8 to 15 per 100,000 person-years with an estimated annual increase of 1.8% (95% confidence interval (CI) 1.3–2.2%). From 2002 to 2010 the rates decreased from 15 to 10 per 100,000 person-years with an annual decrease of 5.4% (95% CI 3.2–7.5%). Age-specific incidence rates were at maximum around the age of 9 years during the whole period. The estimated cumulative incidence proportion at age 16 years based on the 2010 age-specific incidence rates was 0.16% (95% CI 0.09–0.32%) compared with 0.20% (95% CI 0.11–0.37%) based on the 2000 age-specific incidence rates. Conclusion: From 2002 to 2010 there was a decrease in the incidence rate of first-time surgically treated middle ear cholesteatoma. The decrease was preceded by a significant increase in the incidence rate of middle ear ventilation tube insertion. However, further studies are needed to find possible explanations for the decrease. ß 2014 Elsevier Ireland Ltd. All rights reserved.

Keywords: Cholesteatoma Children Incidence rates Denmark Epidemiology

1. Introduction Middle ear cholesteatoma is a severe disease that can cause serious complications and requires meticulous surgical removal. Compared with adult cholesteatoma, childhood cholesteatoma may be of a more aggressive nature with higher rates of recidivism [1]. A generally accepted theory in the development of cholesteatoma is that negative middle ear pressure causes a retraction pocket to be formed in the tympanic membrane. As the pocket deepens, desquamated keratin cannot be cleared and a cholesteatoma is formed [2].

Due to the rarity of cholesteatoma, procuring material of suffice size for epidemiologic studies can be a challenge. In Denmark there is a long tradition for national registration; which together with the unique civil registration number assigned to all persons living in Denmark since 1968 [3] renders a unique opportunity for epidemiologic studies. The aim of the present study was, on a national basis, to describe temporal trends in the incidence rate of cholesteatoma surgery in Danish children from 1977 to 2010.

2. Materials and methods

* Corresponding author at: Department of ENT Head & Neck Surgery, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense, Denmark. Tel.: +45 6550 3032; fax: +45 6550 3682. E-mail address: [email protected] (B.D. Djurhuus).

Data on cholesteatoma surgery was obtained from the Danish National Patient Register (NPR). The Danish health care system is tax-based and offers free hospital treatment for all residents [4].

http://dx.doi.org/10.1016/j.ijporl.2014.11.020 0165-5876/ß 2014 Elsevier Ireland Ltd. All rights reserved.

Please cite this article in press as: B.D. Djurhuus, et al., Cholesteatoma in Danish children – A national study of changes in the incidence rate over 34 years, Int. J. Pediatr. Otorhinolaryngol. (2014), http://dx.doi.org/10.1016/j.ijporl.2014.11.020

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PEDOT-7370; No. of Pages 4 B.D. Djurhuus et al. / International Journal of Pediatric Otorhinolaryngology xxx (2014) xxx–xxx

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Since 1977 registration of all admissions to public hospitals to NPR has been mandatory. Since 1995 outpatient visits have also been registered. An expansion of a private healthcare sector in Denmark in the 2000s necessitated registration from private hospitals too, which became compulsory in 2003 [5]. Diagnostic coding was performed using WHO’s International Classification of Diseases, while surgical coding was done using the ‘‘Surgical- and Treatment Classification’’ from the Danish Board of Health from 1977 to 1995 and the ‘‘Classification of Surgical Procedures’’ from the Nordic Medico-Statistical Committee hereafter [6]. It can be difficult to determine whether or not cholesteatoma is present in the middle ear or mastoid by otomicroscopy alone. The vast majority of cholesteatoma patients are surgically treated [7] and registration of a surgically treated middle ear cholesteatoma (STMEC) was applied for analysis. Statistics Denmark provided aggregated data on the background population. From 1977 to 2010 the total population increased from 5,079,879 to 5,534,738. In 0–15-year-olds the population decreased from 1,207,484 in 1977 to 941,261 in 1992 and then increased to 1,073,864 in 2010 [8]. The study was approved by the Danish Data Protection Agency (j.no 2007-41-131).

Fig. 1. Age standardized annual incidence rates for first-time surgically treated middle ear cholesteatoma in Danish children 1977–2010 smoothed by moving average (y, year).

3. Statistical methods In the estimation of annual incidence rates, direct age standardization using WHO’s population estimation for 2000– 2025 [9] and annual mean populations were applied. A possible change in the incidence rates over time, as well as the male:female ratio was examined using Poisson regression analysis with the number of first-time STMEC (STMEC1) as the dependent variable; the given population as the exposure variable; and sex and calendar year as explanatory variables. When estimating a possible change in incidence rates with age in one-year strata, an interaction term between age and calendar year was included in the model. An estimate of the cumulative incidence proportion was done by the current life-table method. All data management and statistical analyses were performed using Stata version 13 (StataCorp, College Station, TX).

Fig. 2. Age-specific incidence rates for first-time surgically treated middle ear cholesteatoma covering the last 15 years of the study period, smoothed by moving average. The last 5 years of the study period the incidence peak around the age of 9 years has subsided.

4. Results From January 1, 1977 to December 31, 2010 a total of 5850 STMEC’s distributed among 3874 children aged 0–15 years were identified. The male:female incidence rate ratio for the whole period was 1.5 (95% confidence interval (CI) 1.4–1.6).

4.3. Cumulative incidence proportion The estimated cumulative incidence proportion at age 16 based on the 2010 age-specific incidence rates was 0.16% (95% CI 0.09– 0.32%) compared with 0.20% (0.11–0.37%) based on the 2000 agespecific incidence rates.

4.1. Annual incidence rates 4.4. Number of operations per patient From 1977 to 2002 the age-standardized incidence rate of STMEC1 in 0–15-year-olds increased from 8 to 15 per 100,000 person-years (Fig. 1). Poisson regression analysis showed an annual increase of 1.8% (95% CI 1.3–2.2%, P-value 0.001) in the period. From 2002 to 2010 the age-standardized incidence rate in 0– 15-year olds decreased from 15 to 10 per 100,000 person-years (Fig. 1). Poisson regression analysis showed an annual decrease of 5.4% (95% CI 3.2–7.5%, P-value

Cholesteatoma in Danish children - a national study of changes in the incidence rate over 34 years.

To describe temporal trends in the incidence rate of surgically treated middle ear cholesteatoma in Danish children from 1977 to 2010...
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