Why acute otitis media prevalence is decreasing

Fewer infants today experience acute ear infections than 2 or 3 decades ago, according to researchers from the University of Texas Medical Branch (UTMB) at Galveston, who attribute the drop to improved rates of breastfeeding and vaccination, and lower smoking rates.

The study, published in Pediatrics, involved 367 infants with a total of 887 upper respiratory infections (URI) and 180 episodes of acute otitis media (AOM). They found that in comparison to 20 to 30 years ago, rates of AOM have fallen in 3-month-olds from 18% to 6%; from 39% to 23% in 6-month-olds; and from 62% to 46% in 1-year-olds.

Tasnee Chonmaitree, MD, professor of pediatrics and pathology at UTMB and co-author of both this study and American Academy of Pediatrics’ (AAP’s) 2013 guidance on AOM management, says reducing AOM prevalence is not an easy task.

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“Because otitis media (OM) is a complex and multifactorial disease, reducing its incidence requires many factors. Combination of new bacterial pnemococcal conjugate vaccines (PCVs), routine use of influenza vaccines, increased breastfeeding rate, decreased smoking rates are among the contributing factors,” she says. “Our study identified the 3 most important risk factors for acute otitis media: nasopharyngeal bacterial colonization, frequent common cold, and lack of breastfeeding.”

The UTMB report found that ear infections occurred more often in children with more frequent respiratory infections, with AOM occurring in children with 4.7 URI episodes per year, compared to the 2.3 URI infections that occurred in children with no AOM. Additionally, pathogenic bacterial colonization was “significantly higher” in infants with AOM, according to the report.

All but 2 of the cases of AOM developed within 28 days of an URI, according to the report, with AOM typically occurring 5 days after the onset of an URI.

The researchers also noted that while almost half of the infants involved in the study experienced AOM by age 1 year, receiving pneumococcal conjugate and influenza vaccinations; being breastfed; and living with nonsmokers are powerful preventive measures.

Bacterial cultures collected from the study participants also revealed useful information, with colonization rates with 3 pathogenic bacteria (Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae) increasing with age-most frequently overall in infants with AOM.

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The study revealed bacterial and viral interactions that the authors believe warrant further study. Specifically, researchers found that the presence of M catarrhalis or S pneumoniae increased the risk of URI, but only M catarrhalis was found to interact with human metapneumovirus (MPV), respiratory syncytial virus (RSV), and rhinovirus (RV).

Overall, researchers found that the presence of M catarrhalis and RSV-but not both together-increased URI risk, and RV or MPV increased URI risk compared to M catarrhalis without the virus.

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“The presence of M catarrhalis, RV, or both increased AOM risk, compared with neither; but the presence of RV did not alter AOM risk, compared with presence of M catarrhalis. The presence of M catarrhalis, RSV, or both increased AOM risk, compared with neither. Also, RSV, compared with M catarrhalis, increased AOM risk, but M catarrhalis with RSV decreased AOM risk, compared with RSV without M catarrhalis,” according to the report.

The research team also studied environmental and genetic factors, and found that daycare attendance and having multiple siblings increased the risk of URI. Decreased prevalence of URI, however, was associated with birth after February 2010; exclusive breastfeeding for longer than 6 months; increased duration of breastfeeding; and increased length of time before exclusive formula feeding, according to the report. Although no environmental or genetic connections were drawn to AOM, URI is shown to increase the risk or AOM development.

“Frequent viral infections, bacterial colonization, and lack of breastfeeding are major AOM risk factors. It is likely that medical interventions in the past few decades, such as the use of pneumococcal and influenza virus vaccines, higher breastfeeding rates, and decreased smoking, [also] helped reduce AOM incidence,” the study notes. “Our data point to the significant current morbidity of viral respiratory infections and the clear benefit of breastfeeding in reducing both upper respiratory infection (URI) and AOM, as has been previously shown. Interestingly, we found that infants born after 2010, who received PCV13 in place of PCV7, experienced a decreased URI risk but not AOM risk.”

The American Academy of Family Physicians (AAFP) says AOM cost the healthcare system nearly $2 billion in 1995 in direct costs alone, plus another $1 billion in indirect costs, with 25 million physicians office visits and more than 20 million antimicrobial prescriptions written to treat otitis media. The AAFP says although office visits for otitis media dropped to around 16 million by 2000, the number of antimicrobial prescriptions didn’t decrease at the same rate with a total of 13 million.

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According to the AAP’s 2013 guidelines on AOM, generalized OM remains the most common reason physicians prescribe antibiotics to children in the United States. The AAP says physician visits for OM dropped from 950 per 1000 children to 634 per 1000 children from 1996 to 2006, and the percentage of visits ending in a prescription for antibiotics dropped from 80% in 1995 to 76% in 2006.

“Many factors may have contributed to the decrease in visits for OM, including financial issues relating to insurance, such as copayments, that may limit doctor visits, public education campaigns regarding the viral nature of most infectious diseases, use of the PCV7 pneumococcal vaccine, and increased use of the influenza vaccine,” according at AAP guidance on AOM management. “Clinicians may also be more attentive to differentiating AOM from OM with effusion  resulting in fewer visits coded for AOM and fewer antibiotic prescriptions written.”

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Acute otitis media is diagnosed in children with moderate-to-severe bulging of the tympanic membrane or new onset of otorrhea, recent onset of ear pain, intense erythema or the tympanic membrane, and/or middle ear effusion revealed through pneumatic otoscopy and/or tympanometry.

In managing AOM, AAP recommends a number of measures identified in the UTMB report as preventive measures, including eliminating exposure to passive tobacco smoke and promoting breastfeeding. The AAP goes on to add that avoiding supine bottle feeding and pacifier use in the first 6 months of life may reduce AOM occurrence.

Also included in AAP’s guidance are recommendations for vaccinations like influenza vaccine, which can reduce AOM risk by 30% to 55%, and PCVs, which can reduce AOM risk by roughly 29% in children who receive PCV7 before age 2 years.

Chonmaitree says pediatricians should be aware of all of the risk factors and counsel parents on the importance of additional interventions to prevent URI and AOM, such as avoiding contact with people who are sick and reducing exposure to bacterial and viral infections through choices that may include choosing a small daycare over a larger daycare.