A replication of the relationship between elderly suicide rates and the human development index in a cross-national study.

BACKGROUND A recent cross-national study demonstrated a curvilinear (inverted U-shaped curve) between elderly male suicide rates and the Human Development Index (HDI) fitting the quadratic equation y = a + bx - cx2 where y is the elderly male suicide rate, x is the HDI and a, b and c are constants). This study used only one-year cross-sectional data on suicide rates, and suicide rates can randomly fluctuate year on year. METHODS A study designed to replicate this curvilinear relationship between elderly suicide rates and the HDI was undertaken by: (i) using one-year average of five years data on suicide rates; and (ii) using more recent data on both elderly suicide rates than used in the previous study. Data were ascertained from the World Health Organization and the United Nations. RESULTS There was a significant curvilinear (inverted U-shaped curve) relationship between suicide rates in males aged 65-74 years, males aged 75+ years, females aged 65-74 years and the HDI fitting the quadratic equation y = a + bx - cx2. A similar curvilinear relationship was observed in females aged 75+ years, but the significance level only approached 0.05 level. CONCLUSIONS The replication of the curvilinear (inverted U-shaped curve) relationship between elderly suicide rates and the HDI by using one-year average of five years data on suicide rates suggests that the observed relationship is robust and accurate.