Methodological and statistical problems in sleep apnea research: the literature on uvulopalatopharyngoplasty

A comprehensive review of the literature on the surgical treatment of sleep apnea found 37 appropriate papers (total n = 992) on uvulopalatopharyngoplasty (UPPP). Methodological and statistical problems in these papers included the following: 1) There were no randomized studies and few (n = 4) with control groups. 2) Median sample size was only 21.5; thus statistical power was low and clinically important associations were routinely classified as "not statistically significant". 3) Only one paper presented the confidence bounds that might distinguish between statistical and clinical significance. 4) Because of short follow-up time and infrequent repeat follow-ups, little is known about whether UPPP results deteriorate with time. 5) In at least 15 papers, bias caused by retrospective designs and nonrandom loss to follow-up raised questions about the generalizability of results. 6) Few papers associated polysomnographic data with patient-based quality of life measures. 7) Missing data and missing and inconsistent definitions were common. 8) Baseline measures were often biased because the same assessment was inappropriately but routinely used for both screening and baseline. We conclude that because of these and other problems, there is much that is needlessly unknown about UPPP. It is the responsibility of the research and professional communities to define training, editorial and review procedures that will raise the methodological and statistical quality of published research.