Homogeneity in the relationship of serum cholesterol to coronary deaths across different cultures: 40-year follow-up of the Seven Countries Study

Ancel Keys: The legacy of a giant in physiology, nutrition, and public health

Ancel Keys, whose life spanned over 100 years (1904-2004), made a wealth of seminal scientific and public health contributions. As a physiologist, nutritionist, and public health scientist, he has left his mark on the 20th century by exploring different areas of physiology and nutrition, as well as by contributing to the understanding of basic public health issues. Among his major achievements one can mention in chronological order: studying adaptation to very high altitude, developing the K ration to enable the US military to survive with light but dense food, dissecting the physiology of starvation and nutritional rehabilitation to optimize recovery of functions, uncovering the link between serum cholesterol and heart disease, coordinating the first multi-country epidemiological longitudinal study in nutrition and health, coining the word "body mass index" (BMI), which he showed to be the best body weight index to predict body fat, and promoting the Mediterranean diet for a healthy life style. This review examines the historical events and scientific intrigues that have surrounded Ancel Keys's major classical studies that have ensured him a central place in the history of medical science.

How the Seven Countries Study contributed to the launch and development of cardiovascular epidemiology in Italy. A historical perspective

The Italian research group of the Seven Countries Study of Cardiovascular Diseases (SCS), through the independent use of the national cohorts and data, had the lucky opportunity, starting in the early 1960, to launch the Italian research in epidemiology of cardiovascular diseases (CVD). In this way, the Italian Section of that international study became the first investigation with baseline measurements in various cohorts, subsequent re-examinations, systematic search for morbid events, and follow-up for mortality up to 50 years. A large number of scientific aspects has been tackled including estimates of morbidity and mortality rates, the association of risk factors with cardiovascular events and total mortality, the role of risk factor changes, the use of multivariable models, the role of lifestyle behavior, the determinants of all-cause mortality including risk factors rarely measured in other studies, the identification of characteristics of a condition called Heart Disease of Uncertain Etiology (HDUE), the production of predictive tools for practical use and several other issues. All this has been enhanced by the availability of extremely long follow-up data rarely found in other studies. Field work organization, measurement techniques, diagnostic criteria, data handling and computing had the limitations and difficulties typical of those times, the mid of last century, when CVD epidemiology was at its beginning. All this represented anyhow the start of CVD epidemiology research in the country and was the stimulus to the start of other studies and a valuable collaboration with some of them.

The strength of the multivariable associations of major risk factors predicting coronary heart disease mortality is homogeneous across different areas of the Seven Countries Study during 50-year follow-up

OBJECTIVES

To compare the magnitude of multivariable coefficients and hazard ratios of four cardiovascular risk factors across five worldwide regions of the Seven Countries Study in predicting 50-year coronary deaths.

MATERIAL AND METHODS

A total of 13 cohorts of middle-aged men at entry (40-59 years old) were enrolled in the mid-1900s from five relatively homogeneous groups of cohorts (areas): USA, Finland and Zutphen - the Netherlands, Italy and Greece, Serbia, Japan for a total of 10,368 middle-aged men. The major risk factors measured at baseline were age, number of cigarettes smoked, systolic blood pressure and serum cholesterol. Cox proportional hazards models were solved for 50-year (45 years for Serbia) deaths from coronary heart disease (CHD), and the multivariable coefficients were compared for heterogeneity.

RESULTS

The highest levels of risk factors and CHD death rates were found in Finland and Zutphen - the Netherlands and the lowest in Japan. All four risk factors were predictive for long-term CHD mortality in all regions, except serum cholesterol in Japan where the mean levels and CHD events were lowest. Tests of heterogeneity of coefficients for single risk factors in predicting CHD mortality were non-significant across the five areas. The same analyses for the first 25 years of follow-up produced similar findings.

CONCLUSIONS

The strength of the multivariable associations of four major traditional CHD risk factors with long-term CHD mortality appears to be relatively homogeneous across areas, pending needed further evidence.

Re-calibration of coronary risk prediction: an example of the Seven Countries Study

We aimed at performing a calibration and re-calibration process using six standard risk factors from Northern (NE, N = 2360) or Southern European (SE, N = 2789) middle-aged men of the Seven Countries Study, whose parameters and data were fully known, to establish whether re-calibration gave the right answer. Greenwood-Nam-D'Agostino technique as modified by Demler (GNDD) in 2015 produced chi-squared statistics using 10 deciles of observed/expected CHD mortality risk, corresponding to Hosmer-Lemeshaw chi-squared employed for multiple logistic equations whereby binary data are used. Instead of the number of events, the GNDD test uses survival probabilities of observed and predicted events. The exercise applied, in five different ways, the parameters of the NE-predictive model to SE (and vice-versa) and compared the outcome of the simulated re-calibration with the real data. Good re-calibration could be obtained only when risk factor coefficients were substituted, being similar in magnitude and not significantly different between NE-SE. In all other ways, a good re-calibration could not be obtained. This is enough to praise for an overall need of re-evaluation of most investigations that, without GNDD or another proper technique for statistically assessing the potential differences, concluded that re-calibration is a fair method and might therefore be used, with no specific caution.

A Contemporary Review of the Relationship between Red Meat Consumption and Cardiovascular Risk

Cardiovascular diseases burden is increasing due to aging populations and represents one of the major health issues worldwide. Dietary habits have been extensively studied in the cardiovascular field despite the difficulty in the quantification of the assumption of each single food and the observation that several foods affect cardiovascular risk with opposite effects. Moreover, some older findings have been reverted by more recent studies. Red meat has been widely studied in this context, and it has been suggested to increase cardiovascular risk primarily by causing dyslipidemia. Our aim is to review the relationship between red meat assumption and cardiovascular risk and to present novel findings regarding their link.

Association between worldwide dietary and lifestyle patterns with total cholesterol concentrations and DALYs for infectious and cardiovascular diseases: an ecological analysis

Global dietary and lifestyle trends are primary risk factors for communicable and non-communicable diseases. An ecological analysis was conducted to examine the association of global dietary and lifestyle patterns with total cholesterol concentrations. This study also investigated whether total cholesterol modified the association between dietary and lifestyle habits with disability-adjusted-life-years-lost (DALYs) for infectious and cardiovascular diseases (CVDs). Country-specific mean total cholesterol concentrations and DALYs for infectious and CVDs were obtained. Data were then matched to country-specific food and energy availability for consumption and information on obesity, physical inactivity, urbanization, gross domestic product (GDP), life expectancy and smoking. Stepwise multiple regression models were developed to identify significant predictors of total cholesterol concentrations and DALYs for infectious and CVDs.

Life expectancy and egg and meat consumption were significantly associated with cholesterol concentrations. DALYs for infectious diseases were associated with smoking, life expectancy and per capita GDP. Smoking was the only predictor of DALYs for CVDs. The improvement of socio-demographic conditions and economic growth is likely to reduce the burden of communicable diseases in developing countries. A concurring increase in non-communicable diseases is expected, and these results have, yet again, identified smoking as a primary risk factor for CVDs.

The role of n - 6 and n - 3 polyunsaturated fatty acids in the manifestation of the metabolic syndrome in cardiovascular disease and non-alcoholic fatty liver disease

Cardiovascular disease (CVD) and non-alcoholic fatty liver disease (NAFLD) are manifestations of the metabolic syndrome. CVD remains the number one cause of mortality in the West, while NAFLD is the most common liver disease. Growing evidence suggests that polyunsaturated fatty acids (PUFA) influence risk factors including circulating lipids and inflammation on the development of CVD and NAFLD. N - 6 and n - 3 PUFA are comprised of distinct family members, which are increasingly recognized for their individual effects. Therefore, this review examines what is currently known about the specific effects of the major n - 3 and n - 6 PUFA on CVD and NAFLD. Overall, this review supports a beneficial effect of n - 3 PUFA and highlights distinctive effects between alpha-linolenic acid found in plant oils relative to marine derived eicosapentaenoic acid and docosahexaenoic acid. This review also highlights contrasting health effects between the n - 6 PUFA, linoleic and arachidonic acid.

Risk stratification for sudden cardiac death: current status and challenges for the future

Sudden cardiac death (SCD) remains a daunting problem. It is a major public health issue for several reasons: from its prevalence (20% of total mortality in the industrialized world) to the devastating psycho-social impact on society and on the families of victims often still in their prime, and it represents a challenge for medicine, and especially for cardiology. This text summarizes the discussions and opinions of a group of investigators with a long-standing interest in this field. We addressed the occurrence of SCD in individuals apparently healthy, in patients with heart disease and mild or severe cardiac dysfunction, and in those with genetically based arrhythmic diseases. Recognizing the need for more accurate registries of the global and regional distribution of SCD in these different categories, we focused on the assessment of risk for SCD in these four groups, looking at the significance of alterations in cardiac function, of signs of electrical instability identified by ECG abnormalities or by autonomic tests, and of the progressive impact of genetic screening. Special attention was given to the identification of areas of research more or less likely to provide useful information, and thereby more or less suitable for the investment of time and of research funds.

DASH eating pattern is associated with favorable left ventricular function in the multi-ethnic study of atherosclerosis

OBJECTIVE

Potential associations between consistency with the Dietary Approaches to Stop Hypertension (DASH) diet and preclinical stages of heart failure (HF) in a large multiethnic cohort have not been evaluated. This study sought to determine the cross-sectional relationship between the DASH eating pattern and left ventricular (LV) function in the Multi-Ethnic Study of Atherosclerosis (MESA).

DESIGN

A total of 4506 men and women from four ethnic groups (40% white, 24% African American, 22% Hispanic American, and 14% Chinese American) aged 45-84 years and free of clinical cardiovascular disease (CVD) were studied. Diet was assessed using a validated food-frequency questionnaire. LV functional parameters including end-diastolic volume, stroke volume, and LV ejection fraction were measured by magnetic resonance imaging. Multivariate analyses were conducted to examine the association between LV function and DASH eating pattern (including high consumption of fruits, vegetables, whole grains, poultry, fish, nuts, and low-fat dairy products and low consumption of red meat, sweets, and sugar-sweetened beverages).

RESULTS

A 1-unit increase in DASH eating pattern score was associated with a 0.26 ml increase in end-diastolic volume and increases of 0.10 ml/m(2) in stroke volume, adjusted for key confounders. A 1-unit increase in DASH eating pattern score was also associated with a 0.04% increase in ejection fraction, but the relationship was marginally significant (p = 0.08).

CONCLUSIONS

In this population, greater DASH diet consistency is associated with favorable LV function. DASH dietary patterns could be protective against HF.

An International Atherosclerosis Society Position Paper: global recommendations for the management of dyslipidemia--full report

An international panel of the International Atherosclerosis Society has developed a new set of recommendations for the management of dyslipidemia. The panel identifies non--high-density lipoprotein cholesterol as the major atherogenic lipoprotein. Primary and secondary prevention are considered separately. Optimal levels for atherogenic lipoproteins are derived for the two forms of prevention. For primary prevention, the recommendations emphasize lifestyle therapies to reduce atherogenic lipoproteins; drug therapy is reserved for subjects at greater risk. Risk assessment is based on estimation of lifetime risk according to differences in baseline population risk in different nations or regions. Secondary prevention emphasizes use of cholesterol-lowering drugs to attain optimal levels of atherogenic lipoproteins.

A review of the reporting and handling of missing data in cohort studies with repeated assessment of exposure measures

BACKGROUND

Retaining participants in cohort studies with multiple follow-up waves is difficult. Commonly, researchers are faced with the problem of missing data, which may introduce biased results as well as a loss of statistical power and precision. The STROBE guidelines von Elm et al. (Lancet, 370:1453-1457, 2007); Vandenbroucke et al. (PLoS Med, 4:e297, 2007) and the guidelines proposed by Sterne et al. (BMJ, 338:b2393, 2009) recommend that cohort studies report on the amount of missing data, the reasons for non-participation and non-response, and the method used to handle missing data in the analyses. We have conducted a review of publications from cohort studies in order to document the reporting of missing data for exposure measures and to describe the statistical methods used to account for the missing data.

METHODS

A systematic search of English language papers published from January 2000 to December 2009 was carried out in PubMed. Prospective cohort studies with a sample size greater than 1,000 that analysed data using repeated measures of exposure were included.

RESULTS

Among the 82 papers meeting the inclusion criteria, only 35 (43%) reported the amount of missing data according to the suggested guidelines. Sixty-eight papers (83%) described how they dealt with missing data in the analysis. Most of the papers excluded participants with missing data and performed a complete-case analysis (n=54, 66%). Other papers used more sophisticated methods including multiple imputation (n=5) or fully Bayesian modeling (n=1). Methods known to produce biased results were also used, for example, Last Observation Carried Forward (n=7), the missing indicator method (n=1), and mean value substitution (n=3). For the remaining 14 papers, the method used to handle missing data in the analysis was not stated.

CONCLUSIONS

This review highlights the inconsistent reporting of missing data in cohort studies and the continuing use of inappropriate methods to handle missing data in the analysis. Epidemiological journals should invoke the STROBE guidelines as a framework for authors so that the amount of missing data and how this was accounted for in the analysis is transparent in the reporting of cohort studies.

Prevalence of dyslipidemia and goal attainment after initiating lipid-modifying therapy: a Thai multicenter study

Previous studies focused on attaining low-density lipoprotein cholesterol (LDL-C) goals after lipid-modifying therapy (LMT), but data on achieving normal levels of triglyceride and high-density lipoprotein cholesterol (HDL-C) are limited. We reviewed medical records of patients initiated on LMT. High risk was defined as patients with coronary heart disease, diabetes, or 10-year Framingham risk >20%. Among 806 patients enrolled, 429 were at high risk. Prior to initiation of LMT, 66%, 35%, and 44% overall and 69%, 35%, and 45% in the high-risk group had elevated LDL-C, elevated triglyceride, and low HDL-C, respectively. After 12 months of LMT, 21%, 32%, and 39% overall and 26%, 25%, and 43% in the high-risk group still had elevated LDL-C, elevated triglyceride, and low HDL-C, respectively. Approximately 1 of 5 patients continued to experience elevated LDL-C coupled with elevated triglyceride and/or low HDL-C. In conclusion, a substantial proportion of patients initiated on LMT continued to have lipid abnormalities.