Trends and social patterning of CVD and associated risk factors
Socio-economic patterning of cardiovascular disease risk factors in the Scottish population
Coronary heart disease mortality at younger ages appears to have recently levelled out, particularly amongst the most disadvantaged. Examining changes, or even stagnation, in the prevalence of cardiovascular risk factors could provide some explanation for these unfavourable trends. We used the Scottish Health Surveys to investigate how the socio-economic patterning of cardiovascular disease risk factors and biomarkers had changed between 1995 and 2008. We found that there has been at best only moderate declines in the prevalence of behavioural risk factors and no change in their socio-economic patterning, notable for smoking and poor diet. There has, however been an increase in self-reported conditions predisposing to cardiovascular disease. We also found that there has been a substantial increase in the prevalence of obesity with a persistence of large inequalities. At the same time, the prevalence of hypertension has made a small decline, while that of hypercholesterolaemia had declined substantially, albeit from a very high level. Inequalities were generally smaller and, in the case of cholesterol in men, ill defined.
Further work explored what contribution changes in population wide risk factors and changes in treatment uptake made to the decline in CHD mortality in Scotland from 2000 to 2010? By 2010 there were 5770 fewer deaths from CHD in Scotland than would have been expected had mortality rates remained unchanged since 2000. Improvements in medical treatments accounted for nearly half of this decline, and this fall was evenly distributed across socioeconomic groups. Improvements in risk factors such as systolic blood pressure were partially offset by increases in diabetes and obesity.
Lifestyle and socio-economic gradients in coronary heart disease
Coronary heart disease is known to be strongly associated with social status. Since lifestyle – such as smoking, drinking, diet and exercise – impacts on health and is also independently linked with social status, individuals’ health-related habits may drive the associations between coronary heart disease and social status. We aimed to quantify the relative individual and combined contributions of lifestyle factors to such inequalities. We assessed the association between hospital admission or death from coronary heart disease and social class and how it is explained by aspects of lifestyle, providing valuable insights for tackling socio-economic inequalities in health.
Obesity is increasingly prevalent in the Scottish population and the impact this trend will have on health is of concern. Body mass index (BMI), waist circumference and waist-hip ratio are measures commonly used in epidemiological surveys to assess obesity. We used the 1995, 1998 and 2003 Scottish Health Surveys, linked to death records, to investigate the association between mortality and these three indices of body size; after adjusting for age, gender, alcohol consumption, smoking behaviour and year of survey participation. We showed that BMI-defined obesity (>30 kgm-2) was not associated with higher all-cause mortality whereas overweight (25-30 kgm-2) was associated with lower all-cause mortality than the normal BMI range of 18.5-25 kgm-2. Despite there being an increased risk of cardiovascular disease (CVD) mortality associated with BMI-defined obesity, there was insufficient evidence of a relationship with coronary heart disease (CHD). Elevated waist circumference and waist-hip ratio were both associated with higher all-cause, CVD and CHD mortality. Waist circumference and waist-hip ratio identified an increased risk of death amongst those individuals above the widely accepted thresholds for obesity. This may reflect the ability of these two measurements to summarise the amount of abdominal fat a person has. A large quantity of such fat is believed to be particularly detrimental to health, especially in relation to cardiovascular disease. Body mass index not only doesn't distinguish how fat is distributed but also is known to misclassify many individuals as overweight or obese. In epidemiological studies it might be prudent to not rely on just body mass index as a marker of body size.
Subsequent analysis showed that although BMI-defined obesity was not associated with CHD mortality, it was with an elevated risk of CHD incidence. This would imply that excess adiposity is associated with a significant increase in the risk of a CHD event occurring, but not of that event being fatal. Avoidance of fatality during, and following, an event could be related to not only its severity but also timely use of evidence-based medical interventions that have been developed over recent decades.
Social and geographical patterning of coronary heart disease
In Scotland, Coronary Heart Disease (CHD) is still the largest cause of death and is a major contributor to inequalities in mortality. Consequently, it remains a priority research area for both NHS Scotland and the Department of Health. The aim of this project was to examine social and geographical patterning of Coronary Heart Disease in Scotland. Using the system of linked Scottish Morbidity Records (SMR) we found the socioeconomic gradient in first acute myocardial infarction (AMI) events had increased and was stronger in women and at younger ages. Many of the high proportion of AMIs (48%) which resulted in death on the day of the first event were sudden cardiac deaths. Short-term case fatality (within 28 days of the event) improved between 1988 and 2004, perhaps reflecting treatment advances and reductions in first AMI severity, but socioeconomic and geographical inequalities persisted.