Selective internal migration. Does it explain Glasgow's worsening mortality record?

The mortality difference between Glasgow and the rest of Scotland has been increasing and mortality rates are higher than Glasgow's excess deprivation would suggest. One plausible explanation for this excess is selective migration. A sample of 137,073 individuals aged 15 to 64 in 1991 from the Scottish Longitudinal Study was used to test this explanation. Three geographic areas were compared: Glasgow; Aberdeen, Dundee and Edinburgh cities combined and the rest of Scotland. The impact of selective migration was assessed by calculating age and sex standardised mortality rates for 2001/03 by residence in 2001 and by residence in 1991. Glasgow experienced the greatest loss of population (-7.1%) between 1991 and 2001 but this was not strongly related to deprivation. It had the highest mortality at baseline and the difference between it and the other areas increased over the ten years. This pattern was not significantly affected by calculating death rates according to area of residence at 1991 or in 2001. Our results suggest that the increasing difference in mortality rates between Glasgow and the rest of Scotland over this period was probably not caused by selective migration.