Further evidence for epidemiological transition hypothesis for elderly suicides

BACKGROUND: A developmental model of epidemiological transition for elderly suicide rates with four sequential stages has been developed to simultaneously explain cross-national variations in elderly suicide rates, trends over time for elderly suicide rates and age-associated trends in suicides rates reported in the literature. This model was supported by demonstration of a curvilinear (inverted U-shaped curve) relationship between elderly suicide rates and socio-economic status fitting the quadratic equation Y = A + BX - CX2 (where Y is the suicide rate, X is the socio-economic status and A,B, and C are constants) in both sexes. However, this relationship was derived from a cross-sectional study and, therefore, only an association can be inferred. One way to substantiate this further would be to examine the above curvilinear relationship between suicide rates and socio-economic status in a series of younger age-bands because a large part of the epidemiological transition hypothesis was contingent upon the impact of socio-economic status, through a series of mechanisms, on life expectancy. It was hypothesized that the curvilinear (inverted U-shaped curve) relationship between suicide rates and socio-economic status would be absent in younger age-bands and may be present in the younger age-bands closer to the older age-bands (i.e. 45-54 years and 55-64 years). METHODS: The curvilinear relationship between suicide rates in five age-bands 15-24 years to 55-64 years in both sexes and gross national domestic product (GDP), a measure of socio-economic status, fitting the above quadratic equation was examined with curve estimation regression model using data from the World Health Organization. RESULTS: In males in the age-bands 35-44 years, 45-54 years and 55-64 years there was a statistically significant curvilinear (inverted U-shaped curve) relationship with GDP and fitted the quadratic equation Y = A + BX - CX2; this relationship was absent in males in the age-bands 15-24 years and 25-34 years. In females in the age-bands 45-54 years and 55-64 years there was a statistically significant curvilinear with GDP (inverted U-shaped curve) and fitted the quadratic equation Y = A + BX - CX2; this relationship was absent in females in the age-bands 15-24 years, 25-34 years and 35-44 years. CONCLUSIONS: Although caution should be exercised in accepting the model of the epidemiological transition hypothesis for elderly suicide rates because it had been generated from cross-sectional data using an ecological design, the findings of the current study of suicide rates in younger age-bands provide support for this hypothesis.