Excess mortality in the Glasgow conurbation: exploring the existence of a Glasgow effect

Introduction There exists a ‘Scottish effect’, a residue of excess mortality that remains for Scotland relative to England and Wales after standardising for age, sex and local area deprivation status. This residue is largest for the most deprived segments of the Scottish population. Most Scottish areas that can be classified as deprived are located in West Central Scotland and, in particular, the City of Glasgow. Therefore the central aim of this thesis is to establish the existence of a similar ‘Glasgow effect’ and identify if the relationship between deprivation and all cause mortality is different in Glasgow to what is in other, comparable cities in the UK. Methods A method to compare the deprivation status of several UK cities was devised using the deprivation score first calculated by Carstairs and Morris. The population of mainland UK was broken into deciles according to the Carstairs score of Scottish postcode sectors and English wards. Deprivation profiles for particular cities were drawn according to the percentage of the local population that lived in each Carstairs decile. Using data from the three censuses since 1981, longitudinal trends in relative deprivation status for each city could be observed. Analysis of death rates in cities was also undertaken. Two methods were used to compare death rates in cities. Indirect standardisation was used to compare death rates adjusting for the categorical variables of age group, sex and Carstairs decile of postcode sector or ward of residence. Negative binomial models of death counts in small areas using local population as the exposure variable were also created; such models allow the calculation of SMRs with adjustment for continuous variables. Covariates used in these models included city of residence, age group, sex, Carstairs z-score and also the z-scores for each of the four variables from which the Carstairs score is comprised (lack of car ownership, low social class, household overcrowding and unemployment). Results The deprivation profiles confirmed that all UK cities have a high proportion of deprived residents, although some cities have far higher proportions than others. Some cities appeared to show relative improvement in deprivation status over time whilst others seemed resistant to change. Glasgow was the most deprived city at all census time points and the Clydeside conurbation was also more deprived than all other conurbations. SMRs calculated by indirect standardisation indicated that many cities have excess mortality compared to the whole of the UK when adjusting for age group and sex only. Three cities, Glasgow, Liverpool and Manchester, had SMRs that were significantly higher than all other cities at every census time point. Adjusting SMRs for Carstairs deprivation decile diminished the magnitude of this excess mortality in most cities. However, adjusting for Carstairs decile did not diminish the excess mortality in Glasgow sufficiently and there remained a significant, unexplained residue of excess mortality in Glasgow. SMRs generated by regression models adjusting for continuous variables were able to reduce the size of the excess mortality in most cities, though the model producing the lowest SMR varied from place to place and from time to time. In Glasgow, a regression model including age group, sex and lack of car ownership as covariates explained most of the excess mortality at all three time points. Discussion and Conclusion The relationship between deprivation (as measured by the Carstairs index) and death rates in Glasgow did appear to be different to other cities, and there seems to be evidence of a Glasgow effect. There are several reasons why this might be the case, including; the Glasgow effect may be apparent rather than real – an artefact of the Carstairs measure of deprivation failing to capture the complex nature of multiple deprivation; The effect may be the result of migration patterns to and from the city; the effect may be the result of historical levels of deprivation; or the effect may result from different behavioural patterns among Glasgow residents compared to residents of other UK cities. In conclusion, the results show that continued efforts by public health professionals, politicians and residents have failed to produce a step change in the city’s relative health status and Glasgow continues to lag some way behind other cities in the UK. The ability of the Carstairs measure to describe multiple deprivation is called into question. Future research should focus on identifying specific causes of mortality that contribute to the Glasgow effect; on qualitative work to identify if there is a distinct set of social norms in deprived neighbourhoods of Glasgow that contribute to unhealthy patterns of behaviour; and on creating a deprivation index that can be used on equivalent units of geographical area in both Scotland and England