Health Expectancy Calculations: A Novel Approach to Studying Population Health in Bulgaria

Article excerpt

Introduction

For many years. life expectancy in almost every country has slowly but steadily been increasing. On the other hand, a rise in chronic disease and disability, especially among the elderly, has also been observed in many countries. This gives rise to an important question: Does the observed increase in life expectancy concur with decreasing morbidity or are the additional years spent in a prolonged state of illness and dependency? In response to this question three theories have been proposed: there will be an increase in morbidity (1-3): a reduction in morbidity is achievable (4, 5); and finally there is the dynamic equilibrium theory, which assumes that the increase of morbidity caused by ageing in the population is balanced by better health in younger generations (6). Unfortunately, studying traditional indicators such as life expectancy and morbidity rates separately does not provide the answer because these measures do not give a sufficiently integrated description of the health status of the population.

As a consequence, increasing efforts have been focused on constructing a novel health indicator that takes into account both mortality and morbidity. This concept of an integrated health indicator was first proposed by Sanders in 1964 (7). In 1971. Sullivan developed a simple computational technique for a "health expectancy index", showing how many years people could expect to live in good health (8, 9). During the past decade, researchers in various countries have tried to measure health along these lines. In 1989, an international network on health expectancy and the disability process (Reseau esperance de vie en santi; REVES) was set up to interpret observed values of health expectancy and to promote the harmonization of calculations (10-12). Recently, a group from Bulgaria joined this network and -- in close cooperation with it -- is trying to clarify the situation in this country, thereby contributing to the process of international comparison of the development of population health.

Materials and methods

With the intention of estimating health expectancy in Bulgaria, a pilot investigation was undertaken in December 1992 in the town of Svishtov. The study included non-institutionalized persons aged [is greater than or equal to] 60 years, in practice almost the complete population of that age. For each age group, a random sample was taken of about 30% of the total recorded in the population register. Data on the sample size are given in Table 1.

Table 1: Population of Svishtov aged [is greater than or equal to] 60 years, by sex and age group, and the proportions of these groups that were included in the study sample

                                     Population size:
Age
(years)                             Males     Females     Total

60-64                                666       741        1407
65-69                                562       641        1203
70-74                                312       407         719
75-79                                143       230         373
80-84                                106       155         261
[is greater than or equal to]85       69       103         172

Total                               1858       2277        4135

                                    % of population in sample:
Age
(years)                              Males     Females     Total

60-64                                25.1       38.6       32.2
65-69                                32.4       37.4       35.1
70-74                                41.7       35.4       38.1
75-79                                27.3       30.9       29.5
80-84                                39.6       31.6       34.9
[is greater than or equal to]85      26.1       21.4       23.3

Total                                31.1       35.7       33.6

The sample drawn in Svishtov reasonably represents the demographic and social composition of the Bulgarian population, although the number in the highest age groups is slightly under-representative. …