Why is mortality higher in Scotland than in England and Wales? Decreasing influence of socioeconomic deprivation between 1981 and 2001 supports the existence of a 'Scottish Effect'

Objectives To determine the degree to which changing patterns of deprivation in Scotland and the rest of Great Britain between 1981 and 2001 explain Scotland's higher mortality rates over that period. Design Cross-sectional analyses using population and mortality data from around the 1981, 1991 and 2001 censuses. Setting Great Britain (GB). Participants Populations of Great Britain enumerated in the 1981, 1991 and 2001 censuses. Main outcome measures Carstairs deprivation scores derived for wards (England and Wales) and postcode sectors (Scotland). Mortality rates adjusted for age, sex and deprivation decile. Results Between 1981 and 2001 Scotland became less deprived relative to the rest of Great Britain. Age and sex standardized all-cause mortality rates decreased by approximately 25% across Great Britain, including Scotland but mortality rates were on average 12% higher in Scotland in 1981 rising to 15% higher in 2001. While over 60% of the excess mortality in 1981 could be explained by differences in deprivation profile, less than half the excess could be explained in 1991 and 2001. After adjusting for age, sex and deprivation, excess mortality in Scotland rose from 4.7% (95% CI: 3.9% to 5.4%) in 1981 to 7.9% (95% CI: 7.2% to 8.7%) in 1991 and 8.2% (95% CI: 7.4% to 9.0%) in 2001. All deprivation deciles showed excess indicating that populations in Scotland living in areas of comparable deprivation to populations in the rest of Great Britain always had higher mortality rates. By 2001 the largest excesses were found in the most deprived areas in Scotland with a 17% higher mortality rate in the most deprived decile compared to similarly deprived areas in England and Wales. Excess mortality in Scotland has increased most among males aged < 65 years. Conclusions Scotland's relative mortality disadvantage compared to the rest of Great Britain, after allowing for deprivation, is worsening. By 1991 measures of deprivation no longer explained most of the excess mortality in Scotland and the unexplained excess has persisted during the 1990s. More research is required to understand what is causing this 'Scottish effect'.