To the Editor: Dr Gould and colleagues1 found evidence of increased mortality among neonates on the weekends vs weekdays, but this difference was no longer significant after adjusting for birth weight. Such an analysis may appear to account for the higher case-mix of preterm infants that may be born on the weekends, and thus be at higher risk for neonatal mortality.
It is possible, however, that the unadjusted observation of an increased risk was an artifactual result of using births on a particular day of the week as the denominator for deaths occurring on that particular day of the week. The day of the occurrence of the death is likely to be a random event and not necessarily related to the day of birth. Differences in the mortality rate on weekends vs weekdays are a function of changes in the number of births, the number of deaths, or both. If fewer neonates are born on the weekend but the same number die, the weekend mortality rate would appear to increase.
Several methods may be used to compensate for the problem of decreased weekend births. One method is to distribute the number of annual births equally across the days of the week and then to calculate an average weekday mortality rate and compare it with an average weekend mortality rate. Another method, described by Spiers and Guntheroth,2 would be to compare the proportion of deaths observed during the week with the expected proportion (0.71 = 5 weekdays/7 total days of week). By using data from Table 1 of Gould et al, we found no difference in the observed proportion of deaths for the weekdays compared with the expected proportion (z = 0.36, P = .72).
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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