The influence of age on sample size calculation in acute pain trials using morphine consumption as an end point.
BACKGROUND
Many trials in acute postoperative pain use morphine consumption as an end point. Age has been shown to have a significant influence on morphine consumption but is rarely considered in end point analysis.


METHODS
Simulation was used to investigate the effect of age on the power of various sample sizes to detect differences in morphine consumption in control and study groups.


RESULTS
The sample sizes required for 80% power were approximately twice that predicted by a sample size program when comparing morphine consumption using a t test without adjustment for age.


CONCLUSIONS
The model suggests that variations in age have a profound effect on sample size. Researchers may need to account for this to prevent both type 1 and type 2 error.
Rural Clinical School, University of Tasmania, Burnie, Tasmania, Australia. mark.reeves@dhhs.tas.gov.au
Mark
M
Reeves
D000367:Age Factors; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000627:therapeutic use*; D003627:Data Interpretation, Statistical; D023381:Endpoint Determination / Q000706:statistics & numerical data*; D006801:Humans; D009020:Morphine / Q000008:administration & dosage / Q000627:therapeutic use*; D010149:Postoperative Pain / Q000188:drug therapy* / Q000453:epidemiology; D012107:Research Design; D018401:Sample Size
D000701:Analgesics, Opioid; D009020:Morphine