Is there a 'Scottish effect' for mortality? Prospective observational study of census linkage studies.

BACKGROUND Scotland's mortality rate is higher than England and Wales' and this difference cannot be explained by differences in area-level socio-economic deprivation. However, studies of this 'Scottish effect' have not adjusted for individual-level measures of socio-economic position nor accounted for country of birth; important as Scottish born living in England and Wales also have high mortality risk. METHODS Data sets (1991-2001 and 2001-2007) were obtained from the Scottish Longitudinal Study and the Office for National Statistics England and Wales Longitudinal Study that both link census records to subsequent mortality. Analysis was limited to those aged 35-74 at baseline with people followed to emigration, death or end of follow-up. RESULTS Those born in Scotland living in either England and Wales or Scotland had a higher mortality rate than the English born living in England and Wales that was not fully attenuated by adjustment for car access and housing tenure. CONCLUSION Adjusting for household-level differences in socio-economic deprivation does not fully explain the Scottish excess mortality that is seen for those born in Scotland whether living in England and Wales or Scotland. Taking a life course approach may reveal the cause of the 'Scottish effect'.