It's not 'just deprivation': why do equally deprived UK cities experience different health outcomes?

BACKGROUND: The link between deprivation and health is well established. However, recent research has highlighted the existence of a 'Scottish effect', a term used to describe the higher levels of poor health experienced in Scotland over and above that explained by socio-economic circumstances. Evidence of this 'excess' being concentrated in West Central Scotland has led to discussion of a more specific 'Glasgow effect'. However, within the UK, Glasgow is not alone in experiencing relatively high levels of poor health and deprivation; Liverpool and Manchester are two other cities which also stand out in this regard. Previous analyses of this 'effect' were also constrained by limitations of data and geography.
OBJECTIVES: To establish whether there is evidence of a so-called 'Glasgow effect': (1) even when compared with its two most similar and comparable UK cities; and (2) when based on a more robust and spatially sensitive measure of deprivation than was previously available to researchers. STUDY DESIGN AND METHODS: Rates of 'income deprivation' (a measure very highly correlated with the main UK indices of multiple deprivation) were calculated for small areas (average population size: 1600) in Glasgow, Liverpool and Manchester. All-cause and cause-specific standardized mortality ratios were calculated for Glasgow relative to Liverpool and Manchester, standardizing for age, gender and income deprivation decile. In addition, a range of historical census and mortality data were analysed.
RESULTS: The deprivation profiles of Glasgow, Liverpool and Manchester are almost identical. Despite this, premature deaths in Glasgow are more than 30% higher, with all deaths approximately 15% higher. This 'excess' mortality is seen across virtually the entire population: all ages (except the very young), both males and females, in deprived and non-deprived neighbourhoods. For premature mortality, standardized mortality ratios tended to be higher for the more deprived areas (particularly among males), and approximately half of 'excess' deaths under 65 years of age were directly related to alcohol and drugs. Analyses of historical data suggest that it is unlikely that the deprivation profile of Glasgow has changed significantly relative to Liverpool and Manchester in recent decades; however, the mortality gap appears to have widened since the early 1970s, indicating that the 'effect' may be a relatively recent phenomenon.
CONCLUSION: While deprivation is a fundamental determinant of health and, therefore, an important driver of mortality, it is only one part of a complex picture. As currently measured, deprivation does not explain the higher levels of mortality experienced by Glasgow in relation to two very similar UK cities. Thus, additional explanations are required.