The conundrum of time trends in stroke

The rise and fall of tobacco smoking and associated rise and fall of coronary atherosclerosis the lethal role of tobacco

In this review two new hypotheses are explored, one, that the decline in coronary heart disease is mainly due to a dramatic decline in the prevalence of underlying atherosclerosis and two, that tobacco smoking has been a much greater influence on atherosclerosis than previously estimated. The major outcome of coronary atherosclerosis is myocardial infarction. Between 1900 and 1960 the prevalence of coronary atherosclerosis dramatically rose in young male soldiers. Between 1960 and 2010 the prevalence of coronary atherosclerosis in young US soldiers equally dramatically fell. Understanding the reasons for this rise and fall offers important insights into the causes of atherosclerosis. In 1960 over 50% of US military personnel were tobacco smokers but by 1988 the rate had reduced to 30%. The increased prevalence of coronary atherosclerosis in young soldiers between 1900 and 1960 was mainly due to increased tobacco smoking. An additional influence was an increase in food and sugar consumption. The fall in atherosclerosis between 1960 and 2010 was probably due to a reduction in tobacco smoking and to a lesser extent, control of hypertension and lowering of high serum total cholesterol. In Western populations up to two thirds of the fall in deaths due to myocardial infarction has been shown to be due to declines in the incidence of heart attacks. Based on the data included in this review it is arguable that the main reason for the fall in the incidence of heart attacks is the fall in the prevalence of underlying coronary atherosclerosis. The adverse influences of tobacco have been well documented. However the enormity of these adverse influences has not been recognised. Over 50% of men continue to smoke tobacco in China, Indonesia, Russia and middle eastern countries. Based on the experience of Western countries over half of these men will die of smoking related conditions.

Long-term trends in cardiovascular disease mortality and association with respiratory disease

The recent decline in cardiovascular disease mortality in Western countries has been linked with changes in life style and treatment. This study considers periods of decline before effective medical interventions or knowledge about risk factors. Trends in annual age-standardized death rates from cerebrovascular disease, heart disease and circulatory disease, and all cardiovascular disease are reviewed for three phases, 1881–1916, 1920–1939, and 1940–2000. There was a consistent decline in the cerebrovascular disease death rate between 1891 and 2000, apart from brief increases after the two world wars. The heart disease and circulatory disease death rate was declining between 1891 and 1910 before cigarette smoking became prevalent. The early peak in cardiovascular mortality in 1891 coincided with an influenza pandemic and a peak in the death rate from bronchitis, pneumonia and influenza. There is also correspondence between short-term fluctuations in the death rates from these respiratory diseases and cardiovascular disease. This evidence of ecological association is consistent with the findings of many studies that seasonal influenza can trigger acute myocardial infarction and episodes of respiratory infection are followed by increased risk of cardiovascular events. Vaccination studies could provide more definitive evidence of the role in cardiovascular disease and mortality of influenza, other viruses, and common bacterial agents of respiratory infection.

Coronary heart disease from a life-course approach: findings from the health and retirement study, 1998-2004

OBJECTIVE

Guided by a life-course approach to chronic disease, this study examined the ways in which childhood deprivation (low parental education and father's manual occupation) may be associated with coronary heart disease (CHD).

METHOD

Multilevel modeling techniques and a nationally representative sample of Americans above age 50 from the Health and Retirement Study (HRS; N = 18,465) were used to examine childhood and CHD relationships over the course of 6 years (1998-2004).

RESULTS

Having a father with </=8 years of education was associated with 11% higher odds of CHD, accounting for demographic characteristics, adult socioeconomic status (SES; education, income, and wealth), CHD risks (diabetes, hypertension, cigarette smoking, and obesity), and other factors (childhood health, exercise, stroke, and marital status).

DISCUSSION

Policies and programs aimed at improving the conditions of poor children and their families may effectively reduce the prevalence of CHD in later life.

A multilevel model for cardiovascular disease prevalence in the US and its application to micro area prevalence estimates

BACKGROUND

Estimates of disease prevalence for small areas are increasingly required for the allocation of health funds according to local need. Both individual level and geographic risk factors are likely to be relevant to explaining prevalence variations, and in turn relevant to the procedure for small area prevalence estimation. Prevalence estimates are of particular importance for major chronic illnesses such as cardiovascular disease.

METHODS

A multilevel prevalence model for cardiovascular outcomes is proposed that incorporates both survey information on patient risk factors and the effects of geographic location. The model is applied to derive micro area prevalence estimates, specifically estimates of cardiovascular disease for Zip Code Tabulation Areas in the USA. The model incorporates prevalence differentials by age, sex, ethnicity and educational attainment from the 2005 Behavioral Risk Factor Surveillance System survey. Influences of geographic context are modelled at both county and state level, with the county effects relating to poverty and urbanity. State level influences are modelled using a random effects approach that allows both for spatial correlation and spatial isolates.

RESULTS

To assess the importance of geographic variables, three types of model are compared: a model with person level variables only; a model with geographic effects that do not interact with person attributes; and a full model, allowing for state level random effects that differ by ethnicity. There is clear evidence that geographic effects improve statistical fit.

CONCLUSION

Geographic variations in disease prevalence partly reflect the demographic composition of area populations. However, prevalence variations may also show distinct geographic 'contextual' effects. The present study demonstrates by formal modelling methods that improved explanation is obtained by allowing for distinct geographic effects (for counties and states) and for interaction between geographic and person variables. Thus an appropriate methodology to estimate prevalence at small area level should include geographic effects as well as person level demographic variables.

Secular trends in mortality by stroke subtype in the 20th century: a retrospective analysis

BACKGROUND

Since both cerebral infarction and coronary heart disease are caused by atherosclerosis, they would be expected to have similar secular trends in mortality. Because differential diagnosis of stroke subtype on routine death certificates is inaccurate, we aimed to estimate secular trends in cerebral infarct and haemorrhage throughout the 20th century, for England and Wales, with data from autopsy studies.

METHODS

We calculated the ratio of cerebral infarct to cerebral haemorrhage from all available sources of autopsy data from the 20th century. These data were used to estimate the ratio of cerebral infarct to haemorrhage for every year, and hence to estimate rates of cerebral infarct and cerebral haemorrhage from the total stroke mortality rate, obtained from the UK Office for National Statistics.

FINDINGS

Data about stroke subtypes from autopsies were available from 1932 to 1999. The ratio of cerebral infarct to cerebral haemorrhage increased fourfold from 0.5 in the 1930s to 2.0 by the 1990s; most of the increase took place between the 1930s and the 1970s. Estimated secular trends suggested that there was a steady fall in mortality from cerebral haemorrhage throughout the 20th century, whereas mortality from cerebral infarct increased to a peak in the 1970s and then fell. Trends in estimated cerebral infarct mortality closely matched those for coronary heart disease mortality.

INTERPRETATION

The closely related trends in cerebral infarct and coronary heart disease suggest common causes, but the very different trend in cerebral haemorrhage shows that its cause probably differs importantly from these conditions.

Influence of socioeconomic circumstances in early and later life on stroke risk among men in a Scottish cohort study

BACKGROUND AND PURPOSE

The purpose of the study was to investigate stroke risk by socioeconomic measures.

METHODS

The analysis was based on a large cohort study of 5765 working men, from 27 workplaces in Scotland, who were screened between 1970 and 1973. Stroke was defined as having a hospital admission with a main diagnosis of stroke or dying of stroke in the 25-year follow-up period.

RESULTS

There were 416 men who had a stroke. Men with manual occupations when screened, on first entering the workforce, men with manual occupations, and men whose fathers had manual occupations had significantly higher rates of stroke than men in the nonmanual categories. Men who left full-time education at age 16 years or under also had significantly higher rates of stroke. Men living in more deprived areas had higher rates of stroke, but the rates were not statistically significant. The most marked difference was in relation to father's social class, and although adjusting for risk factors for stroke attenuated the relative rates, men whose fathers were in manual social classes had higher relative rates of stroke than men whose fathers were in nonmanual classes (adjusted relative rate for father's social class III manual was 1.37 [95% CI 1.03 to 1.81] and for father's social class IV or V was 1.46 [1.09 to 1.96]). Men who were upwardly mobile (father's social class manual, own social class nonmanual) had a rate of stroke similar to that of stable manual men.

CONCLUSIONS

Poorer socioeconomic circumstance was associated with greater stroke risk, with adverse early-life circumstances of particular importance.