Relationship of some risk factors with typical and atypical manifestations of coronary heart disease

Focus on age at death in field epidemiology

Age at death (AD) is an old metric recently re-evaluated for the study of longevity and mainly used in demography. Developed experience using AD in field epidemiology is summarized with cohorts followed-up for variable periods of time, frequently until extinction or close to extinction, a must to correctly adopt this metric. For practical purposes, a small number of examples is reported condensing previously published results to highlight various aspects of the problem. AD became the alternative of overall death rates when comparing cohorts reaching extinction or near extinction. AD was useful to characterize different causes of death in order to describe their natural history and possible etiology. With the use of multiple linear regression, a large number of possible determinants of AD were identified and some combinations of them resulted in large estimated differences in AD of 10 years or more across individuals. AD is a powerful tool to study population samples followed-up until extinction or near extinction. It allows to compare the life-long experience of different populations, to compare the role of different causes of death and to study the determinants of AD that are conditioning longevity.

Cardiovascular Mortality in 10 Cohorts of Middle-Aged Men Followed-Up 60 Years until Extinction: The Seven Countries Study

OBJECTIVES

To investigate mortalities from three major groups of cardiovascular diseases (CVDs) in a pooled cohort and followed up until extinction.

MATERIALS AND METHODS

Ten cohorts of men (N = 9063) initially aged 40-59, in six countries, were examined and followed-up for 60 years. The major CVD groups were coronary heart disease (CHD), cerebrovascular diseases (STROKE) and other heart diseases of uncertain etiology (HDUE).

RESULTS

Death rates from CHD were higher in countries with high serum cholesterol levels (USA, Finland and The Netherlands) and lower in countries with low cholesterol levels (Italy, Greece and Japan), but the opposite was observed for STROKE and HDUE, which became the most common CVD mortalities in all countries during the last 20 years of follow-up. Systolic blood pressure and smoking habits were, at an individual level, the common risk factors for the three groups of CVD conditions, while serum cholesterol level was the most common risk factor only for CHD. Overall, death rates for the pooled CVDs were 18% higher in North American and Northern European countries, while CHD rates were 57% higher in the same countries.

CONCLUSIONS

Differences in lifelong CVD mortalities across different countries were smaller than expected due to the different rates of the three groups of CVD, and the indirect determinant of this seemed to be baseline serum cholesterol levels.

Heart Diseases of Uncertain Etiology: A New Definition of Heart Failure for Epidemiological Studies

It has been a long time since, in the spectrum of ischemic (IHD) or coronary (CHD) heart diseases, a differentiation was performed between the forms presenting with and those without pain [...].

Cardiovascular mortality in Northern and Southern European cohorts of the Seven Countries Study at 60-year follow-up

OBJECTIVES

The aim of this study was to describe and interpret differences in major cardiovascular disease (CVD) mortality during 60 years between Northern European and Southern European cohorts of the Seven Countries Study of Cardiovascular Diseases.

MATERIAL AND METHODS

Northern Europe included two cohorts from Finland and one from the Netherlands, and Southern Europe included two cohorts from Italy and two from Greece, for a total of 2360 and 2792 CVD-free men, respectively, at entry examination. Coronary heart disease (CHD), STROKE and other Heart Diseases of Uncertain Etiology (HDUE) deaths were the outcomes and Cox models were solved separately based on 12 risk factors.

RESULTS

In 60 years, overall death rates were 99.8% in both Northern and Southern Europe and the pooled CVD rates were 46.9% (significantly higher) and 42.2%, respectively: CHD mortality was higher in Northern Europe, whereas STROKE and HDUE mortality were higher in Southern Europe. Significant Cox coefficients for both areas (but not significantly different between areas) were age, smoking habits, SBP and serum cholesterol for CHD, and only age and SBP did so for STROKE and HDUE. Age at death was lower for CHD, intermediate for STROKE and higher for HDUE in both areas.

CONCLUSION

The advantage for Southern Europe was small in terms of overall CVD death rates, but definitely larger in terms of expectancy of life due to the differences in age at death in the three types of CVD mortality. Mean entry levels of serum cholesterol, 50 mg/dl higher in Northern Europe than in Southern Europe are a major culprit of these outcomes.

Association of serum cholesterol with coronary heart disease mortality during 50-year follow-up in ten cohorts of the seven countries study

BACKGROUND AND AIM

The association of serum cholesterol levels with the occurrence of coronary heart disease (CHD) mortality during a follow-up of 50 years was rarely investigated previously. Thus, we took advantage of results at hand in 10 pooled cohorts of men aged 40-59 years from the Seven Countries Study (9063 individuals and 2057 CHD fatal events) and we assessed this.

METHODS AND RESULTS

Cox proportional hazards models were run with CHD fatal events (as dependent variable) and cholesterol levels (as independent variables) at years 0, 10, and 25 (in 5 cohorts). Cumulative events during subsequent decades (cumulative approach: CA) and separately in each subsequent decade (partitioned approach: PA) were analyzed. The ecological correlation of average baseline serum cholesterol levels with CHD mortality was very high (R = 0.97). Serum cholesterol and CHD mortality for 50 years were associated at the individual level, and the association estimated by the Cox's coefficients (and related hazards ratios) was initially strong in both CA and PA, but slightly declined during later decades. Hazards ratios (for a difference of 40 mg/dl) ranged from 1.39 to 1.20 for CA and from 1.39 to 0.80 for PA. Coefficients were larger for CA than for PA and the decline was more evident for the latter. Partitioned coefficient became negative and significant in the last decade (from year 40-50). Coefficients derived from cholesterol levels measured at year 10 of follow-up showed similar trends but their magnitude was smaller.

CONCLUSION

Thus, the relationship of serum cholesterol levels with CHD mortality remained relatively stable during at least 40 years after a single cholesterol measurement at baseline in middle-aged men.

Epidemiology of Heart Disease of Uncertain Etiology: A Population Study and Review of the Problem

Background and objectives: Previous epidemiological studies have identified a group of heart diseases (here called heart diseases of uncertain etiology-HDUE) whose characteristics were rather different from cases classified as coronary heart disease (CHD), but frequently confused with them. This analysis had the purpose of adding further evidence on this issue based on a large population study. Materials and Methods: Forty-five Italian population samples for a total of 25,272 men and 21,895 women, free from cardiovascular diseases, were examined with measurement of some risk factors. During follow-up, CHD deaths were those manifested as myocardial infarction, other acute ischemic attacks, and sudden death of probable coronary origin, after reasonable exclusion of other causes. Cases of HDUE were those manifested only as heart failure, chronic arrhythmia, and blocks in the absence of typical coronary syndromes. Cox proportional hazards models were computed separately for CHD and HDUE, with 11 risk factors as possible predictors. Results: During an average of 7.4 years (extremes 1-16) there were 223 CHD and 150 HDUE fatal events. Male sex, age, smoking habits, systolic blood pressure, serum cholesterol, and plasma glucose were significantly and directly related to CHD events, while high density lipoprotein (HDL) cholesterol was so in an inverse way. The same risk factors were predictive of HDUE events except serum cholesterol and HDL cholesterol. Multivariable hazards ratio of serum cholesterol (delta = 1 mmol/L) was higher in the CHD model (1.24, 95% CI 1.11-1.39) than in the HDUE model (1.03, 0.5% C.I. 0.89-1.19) and the difference between the respective coefficients was statistically significant (p = 0.0444). Age at death was not different between the two end-points. Conclusions: CHD and HDUE are probably two different morbid conditions, only the first one is likely bound to gross atherosclerotic lesions of coronary arteries and linked to blood lipid levels. We reviewed the problem in epidemiological investigations and addressed inflammation as a potential cofactor to differentiate between CHD and HDUE.

Cholesterol metabolism: A review of how ageing disrupts the biological mechanisms responsible for its regulation

Cholesterol plays a vital role in the human body as a precursor of steroid hormones and bile acids, in addition to providing structure to cell membranes. Whole body cholesterol metabolism is maintained by a highly coordinated balancing act between cholesterol ingestion, synthesis, absorption, and excretion. The aim of this review is to discuss how ageing interacts with these processes. Firstly, we will present an overview of cholesterol metabolism. Following this, we discuss how the biological mechanisms which underpin cholesterol metabolism are effected by ageing. Included in this discussion are lipoprotein dynamics, cholesterol absorption/synthesis and the enterohepatic circulation/synthesis of bile acids. Moreover, we discuss the role of oxidative stress in the pathological progression of atherosclerosis and also discuss how cholesterol biosynthesis is effected by both the mammalian target of rapamycin and sirtuin pathways. Next, we examine how diet and alterations to the gut microbiome can be used to mitigate the impact ageing has on cholesterol metabolism. We conclude by discussing how mathematical models of cholesterol metabolism can be used to identify therapeutic interventions.

Lifestyle habits and mortality from all and specific causes of death: 40-year follow-up in the Italian Rural Areas of the Seven Countries Study

OBJECTIVES

Three lifestyle factors were investigated in a population study to explore their relationships with a long-term mortality.

MATERIAL AND METHODS

In a cohort of 1564 men aged 45-64 and examined in 1965 within the Italian Rural Areas of the Seven Countries Study, smoking habits, physical activity at work and eating habits (as derived from factor analysis) were determined. During the follow-up 693 men died in 20 years and 1441 in 40 years.

RESULTS

In Cox proportional hazards models men smoking cigarettes (versus never smokers), those having a sedentary activity (versus the very active) and those following the Diet Score 1, indexing an unhealthy Diet (versus men with a Diet close to the healthy Mediterranean style) had highly significant hazards ratios (HR) in relations with 20- and 40-year mortality from all causes, coronary heart disease (CHD), cardiovascular disease (CVD) and cancer. HR for all causes in 40 years were 1.44 (95% confidence intervals, CI, 1.27 and 1.64) for smokers, 1.43 (CI 1.23 and 1.67) for sedentary people, and 1.31 (CI 1.15 and 1.50) for men with unhealthy diet. Larger HR were found for CHD, CVD and cancers deaths. Combination of 3 unhealthy risk factors versus their absence was associated with 4.8-year life loss in the 20-year follow-up and 10.7-year in the 40-year follow-up.

CONCLUSIONS

Lifestyle behavior linked to physical activity and smoking and eating habits is strongly associated with mortality and survival in middle aged men during long-term follow-up.

The relationship of age, blood pressure, serum cholesterol and smoking habits with the risk of typical and atypical coronary heart disease death in the European cohorts of the Seven Countries Study

OBJECTIVE

To explore whether "typical" coronary heart disease (CHD) such as fatal myocardial infarction and sudden death relate to major cardiovascular risk factors in the same way as the "atypical" CHD, such as fatal heart failure and chronic arrhythmias.

DESIGN AND SETTING

Ten cohorts (6633 cardiovascular disease-free men, aged 40-59) in five European countries were examined, age and three major risk factors were measured (systolic blood pressure, serum cholesterol, and smoking habits) and 35-year mortality data were collected. Proportional hazard models were solved with typical and atypical CHD deaths treated separately.

RESULTS

Death rates from typical and atypical CHD were inversely related among the five countries. Mean age at death was significantly higher for atypical than typical (75.8 versus 71.6 years; p < 0.001). In the multivariate analysis conducted on pools of 5 countries (adjusted for countries), the relationship of risk factors with typical CHD was direct and significant for age (hazard ratio-HR-for 5 years of age 1.44 (95% CI 1.36-1.52)), systolic blood pressure (HR for 20 mm Hg, 1.39 (95% CI 1.32-1.47)), serum cholesterol (HR for 1 mmol/l of 1.22 (95% CI 1.16-1.27)) and smoking habits (HR smokers versus non-smokers of 1.39 (95% CI 1.24-1.57)). For atypical CHD, age had a larger HR of 2.27 (95% CI 2.05-2.52), systolic blood pressure had a smaller HR of 1.28 (95% CI 1.16-1.41), serum cholesterol had an inverse non-significant HR of 0.90 (0.58-1.58) and smoking habits had a larger HR of 1.54 (95% CI 1.26-1.89).

CONCLUSIONS

Age and serum cholesterol were differently related with typical and atypical CHD deaths, suggesting different etiologies for these coronary diseases.

Long-term predictors of survival for the Seven Countries Study cohort from Crete: from 1960 to 2000

BACKGROUND

In 1960, all male inhabitants of a series of villages in rural Crete, born between 1900 and 1919, were invited to participate in the Seven Countries Study. Analysis of 25-year mortality data from the 16 cohorts of participants indicated that the cohort from Crete had the lowest age-standardised all-cause and coronary heart disease death rates.

METHODS

At baseline, 686 Cretan men (98% of those invited) participated in health examinations. Mortality data were collected over 40 years. Time-fixed and updated covariate survival analysis techniques were applied to assess eight cardiovascular disease risk factors as long-term predictors of all-cause and cardiovascular disease mortality.

RESULTS

The median survival time was 32 years. All-cause and cardiovascular mortality rates were 26 and 11 per 1000 person-years, respectively. Age (relative risk 1.11, 95% CI 1.09-1.13), diastolic blood pressure (relative risk 1.02, 95% CI 1.01-1.03), and smoking (relative risk 1.37, 95% CI 1.14-1.64) were positively associated and forced expiratory volume (relative risk 0.50, 95% CI 0.36-0.68) was negatively associated with all-cause mortality. Age (relative risk 1.13, 95% CI 1.09-1.16), diastolic blood pressure (relative risk 1.01, 95% CI 1.001-1.03), and forced expiratory volume (relative risk 0.53, 95% CI 0.32-0.89) were independent predictors of cardiovascular mortality. Serum cholesterol concentration and body mass index were not independently associated with death risk.

CONCLUSIONS

The Cretan cohort displays favourable 40-year survival. Even so, long-term predictors of the hazard of both all-cause and cardiovascular disease mortality are present.