SEUOL, Korea, April 17 -- The average body mass index in a group of children with otitis media with effusion was about 35% higher than among children with no history of ear infection, found researchers here.
Mean cholesterol levels were also significantly higher in the children with otitis media than among unaffected children, Seung Geun Yeo, M.D., Ph.D., of Kyung Hee University, and colleagues, reported in the April issue of the Archives of Otolaryngology -- Head and Neck Surgery.
Although otitis media with effusion, but without earache or fever, has become frequent in children as has obesity, the association between the conditions had not been explored, they said.
Their prospective, nonrandomized case-control study at a university-affiliated hospital included 55 children, ages two to seven (85 boys, 70 girls), who were treated with unilateral or bilateral ventilation tubes for otitis media with effusion.
The children?s BMI, serum triglyceride, and total cholesterol levels were compared with those of a control group of 118 children (76 boys, 42 girls) with no history of ear infection who had operations for conditions other than ear diseases.
The researchers also divided the otitis media children into two groups, obese and non-obese, and compared their treatment paths.
The standards for defining obesity, the researchers wrote, are BMI greater than 95th percentile for age and sex, usually accompanied by elevated triglyceride and total cholesterol levels.
The mean SD BMI for the otitis media children was 22.0 (3.4) versus 16.3 (2.4) (P=0.01) for the controls, the researchers reported.
The mean total cholesterol level was 195.0 mg/dL (31.0) for those with otitis media versus 159.3 mg/dL (26.9) [5.050.80mmol/L versus 4.130.70mmol/L] (P=0.04) for the unaffected children.
However, triglyceride levels did not differ significantly between the groups (109.4 40.4 mg/dL versus 90.0 52.3mg/dL [1.240.46mmol/L versus 1.020.59mmol/L]) (P=0.13), the researchers reported.
Although serum triglyceride and total cholesterol concentrations were higher in obese children, the standards for obesity using total cholesterol levels have not been definitively established, the researchers wrote. Thus for both triglycerides and total cholesterol, obesity was defined as values not within the normal range for age and sex, they said.
For example, using serum triglyceride concentration as the standard, the researchers reported that of children with tube insertion, 34.7% were obese, whereas with total cholesterol as the standard, only 19.2% were obese.
In a sub-group analysis, when serum triglyceride concentration was used to divide the experimental group into obese (54 children, 34.8%) and nonobese children (101 children, 65.2%), the mean serum triglyceride levels were 149.9 mg/dL and 69.0 mg/dL respectively.
When the experimental group was divided into subgroups of obese children (30 children, 19.2%) and nonobese children (125 children, 80.8%) on the basis of total serum cholesterol, the mean total cholesterol concentrations were 226.0 mg/dL versus 164.0 mg/dL respectively.
However, the frequency of ventilation tube insertion did not differ significantly between obese and nonobese children in the sub-group analysis, regardless of whether obesity was determined by BMI (P=0.10), serum triglyceride level (P=0.12), or total cholesterol (P=0.07), the researchers reported.
The occurrence of otitis media with effusion varies widely, being reported as 50% in British children, 33% in children living in Pittsburgh, 8.7% in Japanese children, and 4.5% to 16.4% in Korean children, Dr. Yeo and colleagues wrote.
Factors shown to predispose to the ear infection include upper respiratory infection, age, race, and attendance in day-care centers. In particular, they said, attendance at various types of day-care centers increases the risk of the condition and young age at the time of hospital admission.
Obesity is associated with mild systemic inflammation, accompanied by increases in the concentrations of C-reactive protein, interleukin 6, and other markers of inflammation, the researchers wrote.
Not only is the occurrence of asthma increased in obese patients, the researchers said, but obesity is also a risk factor for airway hyper-responsiveness and increased airway constriction.
However, the underlying mechanisms of how childhood obesity relates to ear infection remains to be explained, Dr. Yeo said.
Besides inflammation, obesity may affect the metabolism of leptin, released by adipocytes, and leptin receptors, which appear to be protective. For example, leptin-deficient mice show reduced resistance to bacterial and virus infection.
Also, Dr. Yeo said, obese children may be less resistant to disease -- ear infection, atherosclerosis, and so forth. Finally, he said, fat tissue around the eustachian tube may affect tube function, although this is not yet proven.
The investigators concluded that the frequency of ventilation tube insertion within the experimental group was not related to obesity, although childhood obesity was significantly higher in the children with otitis media with effusion versus the control group.