The importance of the socioeconomic status of countries for mental disorders in old age: development of an epidemiological transition model.

The prevalence of a disorder is a function of the incidence of the disorder and the duration of the illness (which may remit spontaneously, by treatment or death). The socioeconomic status of societies may influence the incidence and duration of mental illnesses in old age by influencing life expectancy and availability of appropriate healthcare services and treatments (Suh and Shah, 2001). The relationship between a proxy measure of the socioeconomic status (per capita gross national domestic product (GDP)) and (i) the life expectancy, (ii) child mortality rates and (iii) proxy measures of the quality and quantity of available healthcare services (the proportion of GDP spent on health, per capita expenditure on health and child mortality rates) was examined. The WHO website (www.who.int/countries/en/) provided data on these variables for 191 of the 192 countries for the year 2002. The inter-correlations between all the measured variables were examined using Pearson’s correlation coefficient. Because of highly significant inter-correlations between all these variables, multiple linear regression analysis, with the Enter method, was undertaken with per capita GDP as the dependent variable, and all the variables that were significantly correlated with per capita GDP on univariate analysis as the independent variables. Table S1 (available online as supplementary material attached to the electronic version of this letter at www.journals.cambridge.org/jid_IPG) illustrates the inter-correlations between all the measured variables. Multiple linear regression analysis, for males, revealed that the proportion of GDP spent on health (P < 0.00001) and per capita expenditure on health (P < 0.0001) were the only significant predictors of per capita GDP. The findings for females were identical. This suggests that any influence of per capita GDP on the prevalence of mental disorder in old age may be mediated through the availability of appropriate health care services and treatments (as measured by the proxy markers of the proportion of GDP spent on health and per capita expenditure on health). In socioeconomically less developed societies, various diseases (e.g. infectious diseases) associated with poor socioeconomic factors are common causes of death early in life due to paucity of appropriate healthcare services and treatments (Suh and Shah, 2001). This is supported by negative correlations between male and female child mortality rates and the proportion of GDP spent on health and per capita expenditure on health. This would lead to reduced life expectancy and is supported by positive correlations between male and female life expectancy