Natural history, definitions, risk factors and burden of otitis media

In this review, we describe the various forms of otitis media seen in Australia in the two diverse populations of Indigenous and non-Indigenous people, the natural history in these two populations, and the risk factors for otitis media. In addition, we address the social and cost burden of otitis media and its complications in Australia. We have reviewed the major literature on otitis media, especially in the Australian context, to support this discussion.

The terminology used to describe otitis media and its sequelae has changed over the years. Current terminology is consistent with present understanding of the pathogenesis and pathology of the disease.

Acute otitis media (AOM) without perforation involves acute suppurative inflammation with local and systemic symptoms and signs, including otalgia, otorrhoea, fever, irritability, anorexia, vomiting or diarrhoea. The tympanic membrane bulges and is usually opaque, and pneumatic otoscopy reveals little mobility. AOM with perforation refers either to AOM that has perforated the tympanic membrane and caused discharge or otorrhoea from the middle ear within 7 days of infection, or to the presence of discharge through a tympanostomy tube (also known as a ventilation tube or “grommet”) on an acute basis.

Recurrent AOM (RAOM) refers to separate bouts of AOM —three episodes in 6 months, or four to five in 12 months. There are two distinct types of RAOM: that accompanying an upper respiratory tract infection, with total resolution of middle ear fluid between attacks; or recurrent infection with an underlying persistent otitis media with effusion (OME).

OME is the presence of middle ear fluid without symptoms or signs of suppurative infection. It supersedes previous terms, such as serous otitis media, as the effusion may not be serous, and an asymptomatic middle ear effusion can contain bacteria. OME has myriad appearances, including air fluid levels, bubbles or translucent tympanic membrane, but pneumatic otoscopy almost always shows a retracted tympanic membrane with impaired mobility. Despite the lack of acute suppuration, a child with OME may still have discomfort, pressure, shooting pains in the ear, or balance disorder — OME is the commonest cause of balance disorder in childhood.

Chronic suppurative otitis media (CSOM) is defined as a persistent discharge from the middle ear through a tympanic membrane perforation for more than 6 weeks. CSOM may include a chronic perforation with or without acute or chronic otorrhoea.

These definitions are summarised in Box 1.

Otitis media is one of the commonest childhood illnesses, affecting 80% of Australian children overall by the age of 3 years.1 The proportion of Indigenous children suffering otitis media and its complications is disproportionately high; up to 73% by the age of 12 months.2 Non-Indigenous children may be treated expectantly and without antibiotics and 80% will be symptom-free in 3 days (although middle ear effusion may remain), whereas Indigenous children may suffer RAOM that leads to chronic otorrhoea and CSOM. This dichotomy necessitates different perspectives on the aetiology, pathogenesis and management in the two groups.3

Among non-Indigenous children, the general improvement in socioeconomic conditions and the advent of routine antibiotic therapy for otitis media have led to a decrease in the more serious extracranial and intracranial complications that were seen in the pre-antibiotic era.4 Despite a recrudescence in the incidence of otitis media in the past three decades, related to the increasing use of daycare centres for infants and children, there has been a general tendency in the past 10 years to reduce immediate antibiotic treatment for AOM for children aged over 2 years, exercising a “wait and see” policy.5,6 Among children aged under 2 years, antibiotic therapy results in more rapid resolution of clinical signs (bulging, erythematous tympanic membrane) and symptoms (fever, otalgia, irritability), although even this guideline is being questioned.7

In Australia, surgical management (insertion of grommets or ventilation tubes) for RAOM and OME is the second most common reason for admission to hospital for a procedure in childhood, with 30 126 such procedures in the 2006–07 financial year.8 However, among non-Indigenous children, resolution of AOM (with or without antibiotic treatment) is the most common outcome, with the prevalence of middle ear effusion declining from 65% at 2 weeks after onset of infection to 25% at 3 months after onset.9

Indigenous children in both remote and urban settings tend to suffer otitis media earlier, more frequently and severely, and with more serious complications than non-Indigenous children.2,10 In developed countries, Australian Aboriginal and Torres Strait Islander children remain, arguably, the most vulnerable in terms of otitis media prevalence and severity.11,12 There has been no decrease in otitis media complications in this population, in which infective complications — such as CSOM — occur in up to 30% of children in some communities.13 The end result of RAOM, OME and CSOM, when not treated adequately, is significant conductive hearing loss with a resultant speech and language delay, especially where English may be a child’s second or third language. This results in educational problems, social isolation, truancy and ultimately early school-leaving and difficulties gaining employment. Although hearing aids and school sound field systems (where an infrared signal transmits the teacher’s amplified voice through loudspeakers) are theoretically suitable approaches to this problem, in reality, they are of limited help to infants and young children with draining ears. Indigenous children suffer a mean of 32 months of hearing loss in childhood, compared with 3 months among non-Indigenous children. Among Indigenous children, symptoms of otitis media include otalgia, ear rubbing, fever, excessive crying, restless sleep and poor appetite. Traditionally, management regimens have tended to centre on symptoms and symptom relief. This is compounded by the poor access to health care and socioeconomic standards experienced by many Aboriginal and Torres Strait Islander populations, and consequently poses a significant impact and burden of disease, not just for this population but for the Australian population in general.

Why is there such variation in the incidence, onset, severity and complication rates of otitis media between these two populations? Although much of this will be covered in other articles in this supplement, in brief, early invasion of the nasopharynx by encapsulated bacteria overwhelms the immature immune system, leading to a failure to elicit an adequate antibody response. Nasopharyngeal carriage, sustained by biofilm formation and intracellular bacterial colonisation, leads to chronic adenoiditis, rhinitis and middle ear infection via the eustachian tube.14-16 Social conditions, such as poverty, overcrowding, poor nutrition, exposure to cigarette smoke and lack of running water, all have a role to play in perpetuating the milieu conducive to ongoing carriage of pathogenic bacteria throughout the upper respiratory tract.17 These socioeconomic issues must be addressed, but innovative preventive treatments to diminish bacterial carriage also need to be implemented.

Otitis media is, in essence, an infectious disease with bacterial and viral infection in an environment where the host immune response counters infection. The main factors that influence the risk of otitis media developing can be host-related factors or environmental factors (summarised in Box 2).These factors primarily interact in the nasopharynx and eustachian tube. Two systematic reviews of risk factors for AOM and RAOM noted that daycare centre attendance and dummy (pacifier) use were modifiable factors, whereas breastfeeding, presence of siblings, passive smoking, craniofacial abnormalities and the presence of adenoids were probably risk factors.19,20

Otitis media is a common and debilitating condition that affects up to 73% of children by the age of 12 months. In Australia, the difficulty in establishing the incidence and prevalence rates of otitis media in children is due to definitional and diagnostic differences and uncertainty. An estimate of the number of new cases of otitis media in 2008 among all Australians suggested that between 658 006 and 1 615 486 Australians were affected, with 12.8% of these accounted for by Indigenous children.37

Otitis media is one of the most common conditions diagnosed in the primary health care setting, is one of the most common diagnoses resulting in antibiotic prescription for children, and is a major contributor to childhood morbidity. Few children escape experiencing a form of otitis media before they reach school.

Of Australian children aged 14 years and under experiencing otitis media each year, 15 will suffer permanent hearing loss and over 250 000 will experience temporary hearing loss. Further, 60 263 will experience CSOM, of whom 217 will have intracranial complications and 237 will have mastoiditis. A cross-sectional survey of remote communities in 2001 showed a prevalence of 16.5% for CSOM.2 In 2008, treatment costs (mainly general practitioner visits and prescriptions) accounted for between $100 million and $400 million. The estimated net cost of lost wellbeing due to otitis media in 2008 varied between $1.05 billion and $2.6 billion.37

The estimated number of Indigenous Australians with otitis media in 2008 was between 98 097 and 240 841; 12.8% of these cases occurred before the age of 14 years (47 000 children).37 Aboriginal and Torres Strait Islander children are more likely to experience recurrent disease that sets in at a much earlier age than non-Indigenous children.

Aboriginal and Torres Strait Islander children are at particular risk, enduring living standards equivalent to those in developing nations. In Australia, where non-Indigenous populations generally experience high standards of living and health care, Aboriginal and Torres Strait Islander children continue to suffer an unacceptable incidence of ear disease. This inequality has a significant impact on growth, development and education, and the negative social implications remain difficult to measure.