Otitis Media in Greenland: studies on historical, epidemiological, microbiological, and immunological aspects

This thesis describes the different aspects of otitis media (OM) in the population of Greenland viewed in a historical and modern clinical perspective. Chapter 1 outlines the addressed problems and aims while chapters 2 and 3 deal with historical studies and an evaluation of the present knowledge based on the literature. Physical anthropological studies, using skeletal samples of adult Eskimo crania from before and after the colonization of Greenland in 1721 and information about modern living Eskimos (Inuit), have shown that OM sequelae of the temporal bones were significantly less common in pre-colonization Eskimos and that the mean area size of the pneumatized cell system in the temporal bone was significantly larger in pre-colonization Eskimos. These findings indicated an increase in OM after the colonization most likely caused by the social, cultural, habitary, and dietary changes due to increased contact with the outside world. Historical reports after the colonization confirm a high prevalence of OM especially in children. Modern epidemiological studies from the 1960's to 1980's in the Arctic region of Alaska, Canada, and Greenland along with reports from visiting consultant otologists in Greenland almost uniformly mention prevalent OM problems in children as well as in adults. The aim was therefore to further describe the epidemiological pattern of the different OM disease entities (acute OM (AOM), chronic OM (COM), COM with suppuration (CSOM), secretory OM (SOM), and cholesteatoma) and investigate the potentially associated risk factors in especially Greenlandic children because these diseases are primarily established and problematical in childhood. Chapter 4 describes the definitions used in the thesis and chapter 5 describes the studies included. Section 5.1 describes a study of cholesteatoma in Greenlanders. The study revealed an almost similar incidence of hospital treated children with cholesteatoma (6.6 per 100,000) as seen in comparable studies from other parts of the world. Furthermore, childhood cholesteatomas were the most aggressive. The frequency of residuals or recurrences after otosurgical treatment was high with a trend for better results when using the extensive canal wall-down procedure. It could be concluded that these patients urgently need close follow-up for at least five years postoperatively, if not lifelong. Section 5.2 describes a hearing screening survey of 167 school children using school registration charts. A high prevalence of hearing loss (HL) was found. A total of 43% of the children had hearing thresholds exceeding 20 dB at one or more frequencies between 250-8000 Hz in one or both ears, and 19% had the same type of HL in the frequencies 500-2000 Hz. HL was significantly associated with episodes of OM. These findings were in accordance with reports from Alaska and Canada. It is therefore concluded that a hearing screening programme of school children is important and that OM seems to have an impact on hearing in school children in Greenland. In section 5.3 an epidemiological survey is described concerning the prevalence of the different OM disease entities. The survey was carried out in Nuuk and Sisimiut and involved 740 children aged 3, 4, 5, and 8 years. A total of 591 children participated and selection bias was not found when controlling for age, sex, and episodes of AOM. The survey revealed that 52% of children in Nuuk and 54% in Sisimiut had some kind of pathological affection of their middle ear. COM and CSOM were found in 9%, but more prevalent among children in Sisimiut (12%) than in Nuuk (7%). Middle ear effusion (MEE) diagnosed by tympanometry was found in 23% in Nuuk and 28% in Sisimiut while simple tubal dysfunction (STD) was found in 13% and 8%, respectively. MEE and STD were associated with young age. Sequelae of OM was apparent in 11% in both towns. When comparing the results with a 10-year-older, almost similar survey of 142 children, it was evident that the OM situation had not changed in the period between the studies. The survey underlines the need for increased focus on the different OM entities in Greenlandic children. Section 5.4 deals with microbiological aspects. The nasopharyngeal microflora and ear discharge microflora of potential pathogens were evaluated in 54 children with AOM and in 201 control children without AOM. Very high carriage rates expressed qualitatively and semiquantitatively of potentially pathogenio bacteria were found in the nasopharynx of children with AOM (98%) but also in that of the control children (91%) and even in children denoted as being very healthy (94%). However, the same bacterial species were cultured from the nasopharynx and ear discharge as in comparable studies world-wide. Only S. pneumoniae was carried significantly more often in the nasopharynx of AOM children compared with age matched control children. Chlamydiae, M. pneumoniae, adenovirus, respiratory syncytial virus, parainfluenza- type 1, 2, and 3 virus, and influenza- type A and B virus were not major pathogens. In contrast, entero- and rhinoviruses were detected significantly more frequent in nasopharyngeal specimens from AOM children (59%) compared with age matched controls (33%) and also in 29% of the examined ear discharge specimens. It is therefore concluded that the potentially pathogenic bacterial load is early and massive. This alone or in interplay with entero- and rhinovirus infection and occasionally with other viruses may play an important role in the high prevalence of OM among children in Greenland. Section 5.5 deals with an examination of potential risk factors for AOM, recurrent AOM (rAOM), and COM in the same 591 children as studied in section 5.3. Early age at first AOM episode was associated with rAOM episodes (> or = 5 episodes since birth). Thus, the relative risk of developing rAOM was eight times higher if the first episode of AOM occurred before 7 months of age than after 24 months of age. Furthermore, compared with studies elsewhere in the world, a high proportion (40%) of the children in this survey had their first AOM episode during their first year of life and 41% of these children developed rAOM. It was also found that children had an increased risk of AOM, rAOM, or COM when both parents were born in Greenland, when parents also have had OM, when living in very crowded households, and when having experienced a long period of exclusive breast feeding, or when recalling of breast feeding was not possible. Gender, type, and size of housing, insulation standard of housing, daycare, exposure to passive cigarette smoking, and dietary habits were not associated with AOM, rAOM, or COM in the surveyed children. It is concluded that early onset of AOM occurs frequently in Greenlandic children and that a high proportion of these children develop rAOM. The study confirms that AOM is a highly multifactorial disease determined by a number of genetic and environmental factors. Finally, section 5.6 is a hypothesis generating study attempting to explain the high prevalence of early episodes of AOM in community-based children in Nuuk. The hypothesis is based on a possible association between findings of mannose-binding lectin genotypes, early Epstein-Barr virus infections and episodes of AOM, rAOM, or nasopharyngeal colonization with potentially pathogenic bacteria. However, the study does not support any of this hypothesis. In chapter 6, future studies are suggested and chapter 7 presents concluding remarks.

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