Levente Littvay

Should researchers use single indicators, best indicators, or multiple indicators in structural equation models?

BackgroundStructural equation modeling developed as a statistical melding of path analysis and factor analysis that obscured a fundamental tension between a factor preference for multiple indicators and path modeling’s openness to fewer indicators.DiscussionMultiple indicators hamper theory by unnecessarily restricting the number of modeled latents. Using the few best indicators – possibly even the single best indicator of each latent – encourages development of theoretically sophisticated models. Additional latent variables permit stronger statistical control of potential confounders, and encourage detailed investigation of mediating causal mechanisms.SummaryWe recommend the use of the few best indicators. One or two indicators are often sufficient, but three indicators may occasionally be helpful. More than three indicators are rarely warranted because additional redundant indicators provide less research benefit than single indicators of additional latent variables. Scales created from multiple indicators can introduce additional problems, and are prone to being less desirable than either single or multiple indicators.

Effect of genetic and environmental influences on cardiometabolic risk factors: a twin study

BackgroundBoth genetic and environmental factors play a role in the pathogenesis of type 2 diabetes and cardiovascular diseases. The magnitude of genetic and environmental influences may vary in different populations and can be investigated by twin studies.MethodsIn this cross-sectional study, 101 (63 monozygotic and 38 dizygotic) adult twin pairs (n = 202; mean age: 44.3 ± 15.8 years) were investigated. Past medical history was recorded and physical examination was performed. Fasting venous blood samples were taken for measuring laboratory parameters. For assessing heritability of 14 cardiovascular risk factors, the structural equation (A-C-E) model was used.ResultsThe following risk factors were highly (> 70.0%) or moderately (50.0 - 69.0%) heritable: weight (88.1%), waist circumference (71.0%), systolic blood pressure (57.1%), diastolic blood pressure (57.7%), serum creatinine (64.1%), fibrinogen (59.9%), and serum C-reactive protein (51.9%). On the other hand, shared and unique environmental influences had the highest proportion of total phenotypic variance in serum total cholesterol (46.8% and 53.2%), serum HDL-cholesterol (58.1% and 14.9%), triglycerides (0.0% and 55.9%), fasting blood glucose (57.1% and 42.9%), fasting insulin (45.4% and 54.5%), serum uric acid (46.0% and 31.3%), and serum homocysteine (71.8% and 28.2%, respectively).ConclusionSome cardiometabolic risk factors have strong heritability while others are substantially influenced by environmental factors. Understanding the special heritability characteristics of a particular risk factor can substantiate further investigations, especially in molecular genetics. Moreover, identifying genetic and environmental contribution to certain cardiometabolic risk factors can help in designing prevention and treatment strategies in the population investigated.

Ethics and Personality: Empathy and Narcissism as Moderators of Ethical Decision Making in Business Students

Many studies have reported that business students have been more apt to act in self-interested ways when compared to their counterparts in other academic fields. Beginning with the premise that ethical behavior derives in part from personality characteristics, the authors tested whether (a) measures of an empathetic or narcissistic personality predicted self-reported ethical decision making in business students and (b) individual business majors have a tendency to exhibit these personality traits. First, findings demonstrate that empathetic and narcissistic personality traits are significant predictors of ethical decision making. Second, they found that finance majors showed a marked and statistically significant tendency to be less empathetic and more narcissistic as compared to other business students.

The Hungarian Twin Registry

The first Hungarian Twin Registry was established in Budapest in 1970 through the mandatory reporting of multiple-births. In the 1980s a second, volunteer adult registry was also founded. Unfortunately, both registries ceased to exist in the 1990s. Efforts started in 2006 to revive a Hungarian twin registry. The team spearheading this effort reports here on this progress. Currently, the voluntary Hungarian Twin Registry consists of 310 adult twin pairs and multiplets. Current research focuses on cardiovascular and respiratory health and yielded multiple awards and publications. Efforts are on the way to expand into social, psychological, and obesity studies.

Evolutionary Theory and Political Leadership: Why Certain People Do Not Trust Decision Makers

Central to social systems are the attitudes of the rank and file toward those who make political decisions (leaders), and attitudes toward leaders are known to be characterized by two fundamental features. First, the modal attitude is acceptance of the necessity of leaders coupled with acute aversion to leaders who are believed to be motivated by ambition and avarice; second, people are highly variable with some being markedly more sensitive than others to the traits of leaders. But the theoretical basis for these empirical facts has yet to be fully elucidated. In this article, we offer such a theory by drawing on biological evolution and then, using a series of laboratory experiments, provide an empirical test of it. Results are fully consistent with evolutionary theory in showing that people are indeed generally sensitive to leadership traits threatening to the larger group even as certain, expected individuals are a good deal more sensitive than others.

Heritability of central blood pressure and arterial stiffness: a twin study.

Objective: Central blood pressure and aortic stiffness have been consistently reported as strong cardiovascular risk factors. Twin studies by comparing identical with nonidentical twins produce information on the relative contribution of genes and environment. Methods: One hundred and fifty-four monozygotic (MZ) and 42 dizygotic (DZ) twin pairs (age 43 ± 17 years) from Hungary and the United States underwent brachial and central augmentation index (AIx), brachial and central pressure, and aortic pulse wave velocity (PWV) measurements with the invasively validated Arteriograph device. Bivariate Cholesky decomposition models were applied. Results: Age-adjusted, sex-adjusted and country-adjusted heritability was 60.0% for central SBP [95% confidence interval (CI), 44.8–69.6%], 50.1% for aortic PWV (95%CI, 26.0–66.8%), 48.7% for aortic AIx (95%CI, 1.7–74.0%), 46.8% for brachial AIx (95%CI, 1.1–73.8%), 46.7% for central pulse pressure (PP) (95%CI, 12.4–61.4%), and 30.0% for brachial PP (95%CI, 0.0–53.4%). Central SBP and PP had strong bivariate correlations with brachial (r = 0.461 and 0.425) and central AIx (r = 0.457 and 0.419), as well as with aortic PWV (r = 0.341 and 0.292, all P < 0.001). Brachial PP had a weak correlation with brachial AIx (r = −0.118, P < 0.05), central AIx (r = −0.122, P < 0.05), and none with aortic PWV (r = 0.08, P = n.s.). Genetic factors explained a moderate phenotypic correlation between central PP, SBP, brachial SBP and aortic PWV. Conclusions: Central systolic and PPs, brachial PP, AIx, aortic PWV are moderately heritable. A moderate genetic covariance among aortic PWV and central PP, central SBP and brachial SBP was found.

Heritability of non-alcoholic fatty liver disease and association with abnormal vascular parameters: A twin study

Non‐alcoholic fatty liver disease (NAFLD) has been linked to increased cardiovascular morbidity. However, genetic factors have an unclear role in this condition.

Association of body mass index with arterial stiffness and blood pressure components: a twin study.

RATIONALE Obesity, blood pressure and arterial stiffness are heritable traits interconnected to each other but their possible common genetic and environmental etiologies are unknown. METHODS We studied 228 monozygotic and 150 dizygotic twin pairs aged 18-82 years from Italy, Hungary and the United States, of which 45 monozygotic and 38 dizygotic pairs were discordant for body mass index (BMI; intrapair difference (Δ) in BMI ≥ 3 kg/m(2)). Blood pressure components and arterial stiffness were measured by TensioMed Arteriograph. RESULTS Hypertension was more prevalent among obese than non-obese individuals (55% vs. 29%, p < 0.001). Age-, sex- and country-adjusted heritability estimates were high for hemodynamic measures (45%-58%) and BMI (78%). According to bivariate Cholesky decomposition, phenotypic correlations between BMI and blood pressure components (r = -0.15 to 0.24, p < 0.05) were largely explained by additive genetic factors (65%-77%) with the remaining explained by the unique environment. When controlling for genetic factors within all monozygotic pairs, ΔBMI was significantly correlated with Δbrachial systolic blood pressure (SBP) and diastolic blood pressure (DBP), Δmean arterial pressure, and Δaortic SBP (r = 0.15-0.17, p < 0.05). For the same measures, heavier co-twins of BMI-discordant monozygotic pairs had significantly higher values than their leaner counterparts (p < 0.05). CONCLUSION Blood pressure components are moderately correlated with BMI, largely because of shared genetic factors. However, for the association of BMI with brachial SBP and DBP, aortic SBP and mean arterial pressure, acquired, modifiable factors were also found to be important.

Evidence for a Strong Genetic Influence on Carotid Plaque Characteristics An International Twin Study

Background and Purpose— Few family studies reported moderate genetic impact on the presence and scores of carotid plaques. However, the heritability of carotid plaque characteristics remains still unclear. Twin studies more reliably estimate the relative contribution of genes to these traits in contrast to family study design. Methods— One hundred ninety-two monozygotic and 83 dizygotic adult twin pairs (age 49±15 years) from Italy, Hungary, and the United States underwent B-mode and color Doppler ultrasound of bilateral common, internal, and external carotid arteries. Results— Age-, sex-, and country-adjusted heritability was 78% for the presence of carotid plaque (95% CI, 55%–90%), 74% for plaque echogenicity (hypoechoic, hyperechoic, or mixed; 95% CI, 38%–87%), 69% for plaque size (area in mm2 in longitudinal plane; < or >50 percentile; 95% CI, 16%–86%), 74% for plaque sidedness (unilateral or bilateral; 95% CI, 25%–90%), 74% for plaque numerosity (95% CI, 26%–86%), 68% (95% CI, 40%–84%), and 66% (95% CI, 32%–90%) for the presence of plaque in carotid bulbs and proximal internal carotid arteries. No role of shared environmental factors was found. Unique environmental factors were responsible for the remaining variance (22%–34%). Controlling for relevant covariates did not change the results significantly. Conclusions— The heritability of ultrasound characteristics of carotid plaque is high. Unshared environmental effects account for a modest portion of the variance. Our findings should stimulate the search for genes responsible for these traits.

Chronic hepatitis C virus infection associated with autonomic dysfunction.

Background: Impaired autonomic function has been described in patients with chronic liver diseases from different aetiologies, and has proven to be a poor prognostic indicator. To date, it is not known how chronic hepatitis C virus (HCV) infection affects the autonomic nervous system.