In a study of more than 500 patients who required inpatient care, those with a body mass index of 40 or more were nearly three times as likely to die as patients with a normal body mass index, according to Dr. Janice Louie of the California Department of Public Health in Richmond, Calif., and colleagues.
The risk was even greater for those in the upper ranges of extreme obesity, with a body mass index of 45 or more, Louie and colleagues reported in the Feb. 1 issue of Clinical Infectious Diseases.
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The finding shows that obesity itself, not associated problems such as diabetes or high blood pressure, was an independent risk factor for death, and suggests that obese people with influenza-like illness should be promptly and aggressively managed, the authors concluded.
The result of the analysis is not entirely surprising, since several earlier studies had shown that obese H1N1 patients were more likely to need inpatient care and intensive care, Louie and colleagues noted, but it had not been possible to show that obesity itself was the risk.
To clarify the issue, Louie and colleagues analyzed outcomes and risk factors for 1,076 California patients who were in the hospital for at least 24 hours. Of those, 375 were younger than 20, and 82 were pregnant and were excluded from the analysis. Of the remaining 619, body mass index data was available for 534 patients.
The researchers found that 51 percent of those patients were obese, with a body mass index greater than 30, and 19 percent had a body mass index of 40 or higher.
In total, 92 patients died, and of those 56 (or 61 percent) were obese, including 28 (or 30 percent) with a body mass index of 40 or higher. In the latter group, 21 had a body mass index of 45 or greater, Louis and colleagues found.
The researchers cautioned that data were extracted from nonstandard medical records, case ascertainment was based on passive reporting by clinicians, and underreporting may have occurred. As well, height and weight data were more likely to be available for patients who died.