|Article No. 1 - Vol. 28, No. 4 - December 2009|
Both the expansion of life expectancy, within the more or less constant biologically determined life span, as well as the compression of morbidity, i.e., the reduction of the disease burden by postponing the age of onset of chronic infirmity relative to average life duration, are taking place in the populations across the Region of the Americas.
Cerebrovascular diseases (ICD X codes I60 to I69) are among those chronic cardiovascular illnesses for which a great deal of prevention and disease management is available and, indeed, there has been a sustained reduction in mortality due to stroke in most Latin American and Caribbean countries, as well as in North America between 1970 and 2000. Despite these health gains, mortality due to cerebrovascular diseases remains four times greater in Latin American and Caribbean than in North American countries. More importantly, a considerable proportion of deaths originated by cerebrovascular diseases (~22%) occurs prematurely: each year, this untimely burden of mortality represents, on average, 90,000 deaths among people younger than 65 years of age in the Region of the Americas (out of a total burden of more than 400,000 deaths due to this group of cardiovascular causes). And this burden of premature mortality disproportionately affects women.
The reasons for these differences are not well known, although it is suspected that there are significant disparities in the incidence of cerebrovascular events, access to health services, quality of medical care for stroke, and risk-factor control. Map 1 depicts the quintile distribution of proportional premature mortality due to cerebrovascular disease in the countries and territories of the Americas.
Map 1: proportion of deaths due to cerebrovascular disease (ICD X: I60-I69) in persons younger than 65 years of age.
As a way to illustrate the many uses of the PAHO Basic Indicators brochure series to generate evidence in public health, an exploratory analysis of the relationship between premature mortality due to cerebrovascular disease (CVD) and potential socioeconomic inequality determinants, at the ecological level, is presented here.
Figure 1 shows the non-linear inverse relationship between premature mortality due to CVD, as a proportion of the total number of deaths due to CVD, and gross national income per capita, adjusted by purchase power parity; the higher the income, the lower the proportional premature mortality due to CVD; in other words, in the Americas, the wealthier people are more able to compress mortality, i.e., to postpone deaths due to CVD to ages older than 65 years, than the poorer.
Figure 1: Proportional premature mortality due to cerebrovascular disease and gross national income per capita. The Americas, circa 2006.
In a related, but quite singular perspective, Figure 2 shows the non-linear direct relationship between the risk of dying prematurely due to CVD, as measured by the mortality rate, and the magnitude of the ratio of the average income of the richest quintile to the average income of the poorest quintile of the population of the Americas, the so-called 20/20 ratio, a well-known summary measure of the depth of income inequality in a society. Interestingly enough, this exploratory analysis suggests that the deeper the income inequality, the greater the risk of dying prematurely due to CVD.
Figure 2: Premature mortality rate due to cerebrovascular disease and the 20/20 Kuznets income gap ratio. The Americas, circa 2006.
Figure 3 tells us, graphically, how unequally distributed those premature deaths due to CVD are among the countries of the Americas or, more especifically, along the social gradient of the population defined by income level. The concentration index, a robust summary measure of inequality, is -0.16, indicating that premature mortality due to CVD is disproportionately concentrated among the poorer in the social gradient. More especifically, the concentration curve indicates that almost 30% of the premature deaths due to CVD are concentrated in the poorest 20% of the population of the Americas, whereas only 13% of those premature deaths are concentrated in its richest 20%.
Figure 3: Inequality concentration curve of the risk of dying prematurely due to cerebrovascular disease. The Americas, circa 2006.
This exploratory evidence, generated from data available in the Basic Indicators brochure, suggests that the magnitude of premature mortality due to cerebrovascular diseases in the Americas is still considerable and that it is unequally distributed in the population and linked to socioeconomic macrodeterminants. More especifically, poverty and income inequality are main determinants of its magnitude and distribution. Poverty-reduction strategies and inequality-reduction strategies as well may, in fact, contribute to reduce the burden of premature mortality due to cerebrovascular disease.
Source: Information and Health Analysis (HA), Health Surveillance and Prevention and Control of Diseases (HSD). PAHO/WHO.