In this issue of Archives, Rozé and colleagues1 report results from a cohort study of premature infants receiving mechanical ventilation after birth. Among infants treated with prolonged sedation or analgesia, 41 of 97 (42%) had later disability compared with 324 of 1248 (26%) other infants (crude [unadjusted] risk ratio, 1.6; 95% confidence interval, 1.3-2.1). The treated infants had characteristics that might cause disability, such as younger gestational age and more malformations at birth. Should the harmful association between treatment and disability be attributed to the treatment, the characteristics of those who received the treatment, both, or neither?
Cummings P. Propensity Scores. Arch Pediatr Adolesc Med. 2008;162(8):734–737. doi:10.1001/archpedi.162.8.734