Effect of socioeconomic deprivation on intensive care mortality

Introduction

The effect on health of socioeconomic deprivation has been demonstrated in many areas such as risk for myocardial infarction [1]. There is little data on its effect on intensive care mortality. The Scottish Intensive Care Society Audit is a computer-based audit system that all 26 adult general ICUs in Scotland contribute to. Consequently there is a database for the whole country. In Scotland, the socioeconomic deprivation category (DepCat) can be designated by postcode using the Carstairs score [2]. This is based on housing density, car ownership, male unemployment and the head of the household's social class, and ranges from 1 (most affluent) to 7 (most deprived).

Methods

Between 1 January 1995 and 31 December 2000, audit data were collected prospectively on 44,000 consecutive admissions to all adult general ICUs in Scotland. The Information and Statistics Division of NHS Scotland undertook the linkage of the ICU data to hospital activity episodes (Scottish Morbidity Records) and Registrar General death records. All data were standardised for age and sex. The Standardised Mortality Rate (SMR) by DepCat was calculated by comparing the expected and observed mortality for each DepCat. This enabled us to assess the impact of socioeconomic deprivation on outcome of ICU admissions.

Results

A total of 33,337 case records were able to be allocated a DepCat score. The SMR for these patients ranged from 0.97 for DepCat 1 to 1.32 for the most deprived in DepCat 7 (see Table 1).

Table 1 Standardised ICU mortality by deprivation category

Conclusions

Socioeconomic deprivation appears to affect ICU mortality with a worsening mortality with worsening deprivation. The exact causes for this are unclear but may be due to a multitude of small chronic comorbidities such as smoking, obesity, poor nutrition, alcohol abuse, drug misuse rather than severe chronic ill health. More work is, however, required to further evaluate this.