Elsevier

Public Health

Volume 119, Issue 7, July 2005, Pages 616-625
Public Health

A widening health gap in general practice? Socio-economic differences in morbidity between 1975 and 2000 in The Netherlands

https://doi.org/10.1016/j.puhe.2004.08.023Get rights and content

Summary

Background

During the past two decades, socio-economic inequalities in health have been a major research theme in Western Europe. Research has shown that there are persistent differences in health between people with a high socio-economic status (SES) compared with people with a low SES. There are also indications for a widening health gap. The present paper aimed to find out whether this widening health gap exists in The Netherlands using morbidity data from a general practice (GP) registry.

Methods

Incidence data from a GP registry were used, involving over 12,000 patients. Morbidity data from 1975 to 2000 were grouped into 25 disease categories. SES was based on household occupational status. Poisson regression was used to determine the relationship between morbidity and SES and its changes over time. Separate analyses were performed for men and women.

Results

In most disease categories, a clear SES gradient disadvantageous to the lowest-SES group was identified: 17 out of 22 morbidity categories for men and 17 out of 24 for women. For seven (men) and eight (women) morbidity categories out of 17, the SES gradient increased between 1975 and 2000.

Conclusions

This study provides new evidence for a widening gap in health between higher and lower SES in The Netherlands, using GP-defined disease data and a wide range of morbidity categories.

Introduction

In the early 1980s, socio-economic differences in health and accessibility of healthcare became major issues in Western Europe,1, 2, 3, 4 including The Netherlands.5 In most Western European countries, risks of mortality and morbidity are higher in the lower socio-economic status (SES) groups,6, 7, 8, 9, 10, 11, 12 and socio-economic differences in mortality and morbidity appear to have increased over the last 20 years9, 13, 14, 15, 16, 17, 18 with only a few exceptions.19, 20 In Britain, a widening gap in mortality differentials has gone in tandem with growing income inequalities.16

Compared with studies on mortality, most studies on widening health inequalities are from the UK. Persistent inequalities in health have also been identified in The Netherlands. In the past two decades, much research has been performed into this phenomenon. In the 1980s and 1990s, the Dutch government initiated two 5-year research programmes.4, 21, 22 These programmes generated empirical evidence about inequalities in health and mortality in The Netherlands. In general, there is a clear socio-economic gradient in health that is unfavourable to those of lower SES.23, 24, 25 Socio-economic differences have been found in average life expectancy and in the average number of healthy years, both to the detriment of lower-SES groups and lower educational groups. On average, the latter live 3.5 years less and spend 12 fewer years in good health compared with higher educational groups.25 Lower-SES groups have a higher incidence of heart disease, chronic obstructive pulmonary disease, back complaints and diabetes. For a few diseases, i.e. chronic skin disease, eczema and sinusitis, and for screening activities, the relationship is in the opposite direction.26, 27

For The Netherlands, the available evidence on trends in socio-economic differences in morbidity is based on self-reported morbidity and aggregated health measures. Evidence based on registry data by healthcare providers, such as general practitioners (GPs) or hospital doctors, is lacking. Registry data are available only for trends in socio-economic differences in mortality. Research based on these data indicates that socio-economic differences in mortality increased slightly between 1950 and 1980. This may imply that socio-economic health differences also increased during the same period. However, detailed trend analyses of socio-economic health differences on the disease level are lacking.

The current paper examines changes in socio-economic health differences in The Netherlands over a period of almost three decades—from the mid-1970s to 2000—using GP registry data. We will describe the average socio-economic health differences for 25 morbidity categories. We will also investigate whether or not the observed socio-economic health differences have changed over time.

Section snippets

Data

The data used in this study were based on the Continuous Morbidity Registration (CMR);29 a co-operation between the Department of General Practice and Family Medicine of the University of Nijmegen and a network of four general practices located in the eastern part of The Netherlands. Since 1971, all diagnoses made by the participating GPs have been registered. Validity and reliability of the data is constantly monitored by monthly meetings to perform uniformity tests and discuss coding

Methods

Poisson regression (SPSS 10.0) was used to determine the association between SES and morbidity, and the changes in this association between 1975 and 2000. Separate analyses were performed for each disease category and for men and women. All analyses were adjusted for age. To determine the relationship between SES and disease incidence, two models were estimated. One model used SES as an interval variable, assuming equal distances between the lowest- and the middle-SES groups, and between the

Socio-economic differences in morbidity for men

Column two of Table 2 shows the incidence of the disease categories, ranging from seven to 301 per 1000 patients. The third column shows statistically significant effects of SES for 19 out of 22 disease categories. The coefficients in column three are relative risks (RR) with the lower-SES group as the reference category. For 17 of the 19 categories with a significant linear effect, the coefficient was below 1.0, which means that the disease incidence is higher in the lower-SES group. Thus, the

Conclusions

The analyses clearly show that there is a strong influence of SES on presented morbidity in general practice in The Netherlands. In general, we observed that people with a low SES present more complaints to their GP. This finding is in accordance with the literature on socio-economic health differences. However, there are exceptions. For men, chronic skin diseases and disorders of the male genital organs are presented more often by people with high SES. For chronic skin infections, this finding

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