Centre for Epidemiology and Biostatistics, Chinese University of Hong Kong, Shatin, Hong Kong
In a recent issue of the Journal, Karlberg et al. (1) reported on an analysis of severe acute respiratory syndrome (SARS) data from Hong Kong. The authors found a substantial and statistically significantly higher mortality rate for males than for females, which persisted after adjustment for patient age. We wish to report the results of an analysis of similar data from the Taiwan Center for Disease Control (2). After reclassification of the data by World Health Organization case definition and after polymerase chain reaction and SARS antibody testing, the total number of SARS cases in Taiwan during last years epidemic was 346; 73 (21.1 percent) of these patients died, either directly from SARS or from a SARS-related cause (2). The overall mortality rate was higher than that reported for Hong Kong (17.0 percent) (1), and the difference was close to significance (p = 0.079). While it was not possible to directly compare the age distributions of the Hong Kong and Taiwanese patients because of differences in the way patients were grouped by age, the distributions appeared to be roughly similar. In addition, since larger percentages of Taiwanese patients were women (63.0 percent vs. 55.8 percent for Hong Kong) and health-care workers (30.3 percent vs. 21.9 percent for Hong Kong), this higher mortality rate could not have been due to confounding by these variables.
Table 1 shows the distributions of cases and deaths by gender and age group. The 128 Taiwanese male SARS patients had a significantly (p = 0.002) higher mortality rate (30.5 percent) than the 218 female patients (15.6 percent). As in Hong Kong, Taiwanese female patients were significantly (p < 0.0005) younger than males, with 55.0 percent of females versus 37.5 percent of males being under 40 years of age at diagnosis, while 25.0 percent of males versus 10.6 percent of females were over age 60 years.
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The 105 Taiwanese SARS patients who were health-care workers had a mortality rate (11.4 percent) that was significantly (p = 0.0056) lower than that of non-health-care workers (25.3 percent) (2). Given the excess of female SARS patients in the age group 2049 years, it is likely that most of the health-care workers were young women, as was the case for Hong Kong (1). Therefore, the possibility that health-care-worker status is a confounder of the observed gender-mortality relation cannot be excluded. Likewise, confounding by other variables such as comorbid conditions, smoking history, or time from the appearance of symptoms to hospitalization cannot be ruled out.
Editors note: In accordance with Journal policy, Dr. Karlberg and his colleagues were asked whether they wished to respond to this letter, but they chose not to do so.
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