[Mortality socio-economic inequalities for small-areas in Belgium: assessing concentration]

The reduction of socio-economic inequality in mortality is an important public health goal. Previous ecological studies aimed at studying the relationship between mortality rate and socio-economic factors have paid little attention to mortality causes avoidable by primary or secondary prevention. Furthermore, these studies do not make the distinction between, on the one hand, the strength of the relationship mortality/socio-economic deprivation and, on the other hand, the significance of the unequal distribution of mortality. The present work is aimed at measuring the strength of this relationship and the concentration of mortality in relation to socio-economic deprivation for both overall mortality and mortality avoidable by primary and secondary prevention.

Standardised mortality ratios were computed at the community level in Belgium (1985-93 period) for all causes and for 11 mortality causes avoidable by primary and secondary prevention. A deprivation index was elaborated using a factorial principal component analysis on 11 socio-economic indicators. The mortality/deprivation relationship was assessed by way of a standardised regression coefficient (B) while socio-economic concentration of mortality was estimated using the Concentration Illness Index (Cii) and the P90/P10 ratio.

A strong positive relationship was found between mortality and deprivation for under 65 years all-causes mortality (B =0.71; CI [0.66; 0.76]), mortality for cirrhosis of the liver (B =0.56; CI [0.51; 0.62]), lung cancer (B =0.49; CI [0.42; 0. 56]), suicide (B =0.35; CI [0.29; 0.42]) and falls (B =0.34; CI [0. 28; 0.41]). However, the concentration of mortality was more limited: 14% (CI [11%-17%]) of cirrhosis of the liver mortality, 7% of fall (CI [5%-10%]) and suicide mortality (CI [4%-9%]), 6% (CI [5%-7%]) of lung cancer mortality is unequally distributed.

Socio-economic deprivation is positively associated with mortality. This association is more pronounced for tobacco, alcohol and mental health related mortality. However, the strength of the relationship between socio-economic deprivation and mortality is not a good indicator of unequal distribution.