What causes the burden of stroke in Scotland? A comparative risk assessment approach linking the Scottish Health Survey to administrative health data.

BACKGROUND: The availability of robust evidence to inform effective public health decision making is becoming increasingly important, particularly in a time of competing health demands and limited resources. Comparative Risk Assessments (CRA) are useful in this regard as they quantify the contribution of modifiable exposures to the disease burden in a population. The aim of this study is to assess the contribution of a range of modifiable exposures to the burden of disease due to stroke, an important public health problem in Scotland. METHODS: We used individual-level response data from eight waves (1995-2012) of the Scottish Health Survey linked to acute hospital discharge records from the Scottish Morbidity Record 01 (SMR01) and cause of death records from the death register. Stroke was defined using the International Classification of Disease (ICD) 9 codes 430-431, 433-4 and 436; and the ICD10 codes I60-61 and I63-64 and stroke incidence was defined as a composite of an individual's first hospitalisation or death from stroke. A literature review identified exposures causally linked to stroke. Exposures were mapped to the layers of the Dahlgren & Whitehead model of the determinants of health and Population Attributable Fractions were calculated for each exposure deemed a significant causal risk of stroke from a Cox Proportional Hazards Regression model. Population Attributable Fractions were not summed as they may add to more than 100% due to the possibility of a person being exposed to more than one exposure simultaneously. RESULTS: Overall, the results suggest that socioeconomic factors explain the largest proportion of incident stroke hospitalisations and deaths, after adjustment for confounding. After DAG adjustment, low education explained 38.8% (95% Confidence Interval 26.0% to 49.4%, area deprivation (as measured by the Scottish Index of Multiple Deprivation) 34.9% (95% CI 26.4 to 42.4%), occupational social class differences 30.3% (95% CI 19.4% to 39.8%), high systolic blood pressure 29.6% (95% CI 20.6% to 37.6%), smoking 25.6% (95% CI 17.9% to 32.6%) and area deprivation (as measured by the Carstairs area deprivation Index) 23.5% (95% CI 14.4% to 31.7%), of incident strokes in Scotland after adjustment. CONCLUSION: This study provides evidence for prioritising interventions that tackle socioeconomic inequalities as a means of achieving the greatest reduction in avoidable strokes in Scotland. Future work to disentangle the proportion of the effect of deprivation transmitted through intermediate mediators on the pathway between socioeconomic inequalities and stroke may offer additional opportunities to reduce the incidence of stroke in Scotland.

Trends and inequalities in the burden of mortality in Scotland 2000-2015.

BACKGROUND: Cause-specific mortality trends are routinely reported for Scotland. However, ill-defined deaths are not routinely redistributed to more precise and internationally comparable categories nor is the mortality reported in terms of years of life lost to facilitate the calculation of the burden of disease. This study describes trends in Years of Life Lost (YLL) for specific causes of death in Scotland from 2000 to 2015. METHODS: We obtained records of all deaths in Scotland by age, sex, area and underlying cause of death between 2000 and 2015. We redistributed Ill-Defined Deaths (IDDs) to more exact and meaningful causes using internationally accepted methods. Years of Life Lost (YLL) using remaining life expectancy by sex and single year of age from the 2013 Scottish life table were calculated for each death. These data were then used to calculate the crude and age-standardised trends in YLL by age, sex, cause, health board area, and area deprivation decile. RESULTS: Between 2000 and 2015, the annual percentage of deaths that were ill-defined varied between 10% and 12%. The proportion of deaths that were IDDs increased over time and were more common: in women; amongst those aged 1-4 years, 25-34 years and >80 years; in more deprived areas; and in the island health boards. The total YLL fell from around 17,800 years per 100,000 population in 2000 to around 13,500 years by 2015. The largest individual contributors to YLL were Ischaemic Heart Disease (IHD), respiratory cancers, Chronic Obstructive Pulmonary Disease (COPD), cerebrovascular disease and Alzheimer's/dementia. The proportion of total YLL due to IHD and stroke declined over time, but increased for Alzheimer's/dementia and drug use disorders. There were marked absolute inequalities in YLL by area deprivation, with a mean Slope Index of Inequality (SII) for all causes of 15,344 YLL between 2001 and 2015, with IHD and COPD the greatest contributors. The Relative Index of Inequality (RII) for YLL was highest for self-harm and lower respiratory infections. CONCLUSION: The total YLL per 100,000 population in Scotland has declined over time. The YLL in Scotland is predominantly due to a wide range of chronic diseases, substance misuse, self-harm and increasingly Alzheimer's disease and dementia. Inequalities in YLL, in both relative and absolute terms, are stark.