Strengthening the validity of population-based suicide rate comparisons: an illustration using U.S. military and civilian data.

The objectives of this study were to generate precise estimates of suicide rates in the military while controlling for factors contributing to rate variability such as demographic differences and classification bias, and to develop a simple methodology for the determination of statistically derived thresholds for detecting significant rate changes. Suicide rate estimates were calculated for the military population and each service branch over 11 years, directly standardized to the 2000 U.S. population. Military rates were highly comparable across branches and were approximately 20% lower than the civilian rate. Direct adjustment essentially controlled for the demographic confounds in this sample. Applying the Poisson-based method, we demonstrate that suicide rate fluctuations as large as 20-40% in any year may be attributed to random error.