Age-based construct validation using structural equation modeling

Abstract

In this paper we describe some mathematical and statistical models based on structural equation modeling (SEM) using computer programs like LISREL. We focus on SEM methodology for the simultaneous examination of the internal validity of psychological constructs and the external validity represented by age relations. To illustrate these ideas we use a latent variable path model to examine the organization of intellectual abilities measured by the WAIS-R in the standardization sample. We also examine different ways in which age can be used to structure this organization. This is primarily a methodological paper, but we try to integrate conceptual principles of modeling with some substantive issues of research on the psychology of aging.     

Perceived stress as a risk factor for changes in health behaviour and cardiac risk profile: a longitudinal study

Objective. The aim of this study was to evaluate the long‐term effects of stress on changes in health behaviour and cardiac risk profile in men and women. Design. A prospective cohort study. Setting. The Copenhagen City Heart Study, Denmark. Subjects. The analyses were based on 7066 women and men from the second (1981–1983) and third (1991–1993) wave of the Copenhagen City Heart Study. All participants were asked questions on stress and health behaviour and they had their weight, height, blood pressure and level of blood lipids measured by trained personnel. Main outcome measures. Changes in health behaviour (smoking, physical activity, alcohol consumption, overweight) and cardiac risk profile (cholesterol, HDL cholesterol, blood pressure, diabetes). Results. Individuals with high levels of stress compared to those with low levels of stress were less likely to quit smoking (OR = 0.58; 95% CI: 0.41–0.83), more likely to become physically inactive (1.90; 1.41–2.55), less likely to stop drinking above the sensible drinking limits (0.43; 0.24–0.79), and stressed women were more likely to become overweight (1.55; 1.12–2.15) during follow‐up. Men and women with high stress were more likely to use antihypertensive medication (1.94; 1.63–2.30), and stressed men were more than two times as likely to develop diabetes during follow‐up (2.36; 1.22–4.59). Conclusion. This longitudinal study supports a causal relation between stress and cardiovascular diseases mediated through unfavourable changes in health behaviour and cardiac risk profile.     

Diverse cis factors controlling Alu retrotransposition: What causes Alu elements to die?

The human genome contains nearly 1.1 million Alu elements comprising roughly 11% of its total DNA content. Alu elements use a copy and paste retrotransposition mechanism that can result in de novo disease insertion alleles. There are nearly 900,000 old Alu elements from subfamilies S and J that appear to be almost completely inactive, and about 200,000 from subfamily Y or younger, which include a few thousand copies of the Ya5 subfamily which makes up the majority of current activity. Given the much higher copy number of the older Alu subfamilies, it is not known why all of the active Alu elements belong to the younger subfamilies. We present a systematic analysis evaluating the observed sequence variation in the different sections of an Alu element on retrotransposition. The length of the longest number of uninterrupted adenines in the A-tail, the degree of A-tail heterogeneity, the length of the 3′ unique end after the A-tail and before the RNA polymerase III terminator, and random mutations found in the right monomer all modulate the retrotransposition efficiency. These changes occur over different evolutionary time frames. The combined impact of sequence changes in all of these regions explains why young Alus are currently causing disease through retrotransposition, and the old Alus have lost their ability to retrotranspose. We present a predictive model to evaluate the retrotransposition capability of individual Alu elements and successfully applied it to identify the first putative source element for a disease-causing Alu insertion in a patient with cystic fibrosis.     

Quality of life and its correlates in octogenarians. Use of the SEIQoL-DW in Wave 5 of the Aberdeen Birth Cohort 1921 Study (ABC1921)

Background The direct-weighted Schedule for the Evaluation of Individual Quality of Life, Direct Weighting (SEIQoL-DW) is an individualised measure of QoL that has been little used in very elderly people. Methods We administered SEIQoL-DW during Wave 5 of the Aberdeen Birth Cohort 1921 Study (ABC1921) and sought statistical correlations with other variables in the data set. ABC1921 participants had been IQ-tested in 1932 at age 11. Since 1997, data about cognition, mental/physical function, personality, health, and socioeconomic status have been gathered in five waves of investigations. Results Ninety-six out of 98 individuals, mean age 82.2, completed the SEIQoL-DW. Health, family, relationships, finances and social pastimes were the commonest cues nominated, but age/gender differences existed. The mean SEIQoL-DW score (74.0) was significantly lower than in an approximately 60% sample from Wave 3, the fall being greater in men. Variables statistically associated with Wave 5 SEIQoL-DW usually reflected current rather than past status [including Short-Form 36 Health Survey (SF-36) components and depression], although there were weaker correlations with years of education, housing in childhood, conscientiousness, and IQ in 1998. Conclusions SEIQoL-DW proved feasible and acceptable in community-dwelling octogenarians. Recent (i.e. statelike) rather than early or long-standing (i.e. traitlike) influences appeared to have the greater effect on QoL.     

Peristomal complications of paediatric tracheostomy.

Failure of decannulation after paediatric tracheostomy, once the underlying disorder has resolved, is almost always due to peristomal complications. Granulation tissue formation in the raw tissue of the stoma and its subsequent fibrosis requires removal (50 of the 293 tracheostomies from the Red Cross War Memorial Children's Hospital). It is suggested that this can be avoided by creating a formal skin-to-trachea stoma at the time of tracheostomy. Suprastomal depression of the anterior wall of the trachea (52/293) appears to be unavoidable when using standard tracheostomy tubes. Localised stomal site tracheomalacia and stenosis (numbers of this complication are unknown) results from damage to cartilage of the trachea either by incision or by necrosis from pressure of the tracheostomy tube. Trauma to the cartilage needs to be minimised by careful design of the tracheal incision. It is suggested that consideration should be given to creating a formal tracheostomy stoma for any paediatric tracheostomy that is likely to be required for more than a short period of time.     

A prognostic index to predict long-term mortality in patients with mild to moderate chronic heart failure stabilised on angiotensin converting enzyme inhibitors

BACKGROUND: Mortality in patients with mild to moderate chronic heart failure remains high. At present there is no easy way of identifying patients within this population at increased risk of death in the medium to long term. AIMS: To develop a prognostic index to identify outpatients with mild to moderate chronic heart failure at increased risk of death. METHODS AND RESULTS: Five hundred and fifty-three outpatients mean (S.D.) age 63(+/-10) years with symptoms of chronic heart failure (mean New York Heart Association functional class, 2.3(+/-0.5)), were recruited between December 1993 and April 1995. By April 2000, 201 patients had died. Using data from non-invasive measurements of cardiac size, electrical and autonomic function, renal function and plasma biochemistry we identified eight independent predictors of mortality (all P<0.01). To develop a prognostic index, predictors were dichotomised by group median and awarded 0 or 1 point accordingly. Serum sodium /=111 micromol/l (1 point), cardiothoracic ratio >/=0.52 (1 point), SDNN /=487 ms (1 point), QRS dispersion>/=42.7 ms (1 point), the presence of non-sustained ventricular tachycardia (1 point) and voltage criteria for left ventricular hypertrophy on 12-lead ECG (1 point). We calculated risk scores for patients by adding the points of each independent risk factor. In the low-risk group (0-3 points) mortality at 5 years was 20% and in the high-risk group (4-8 points) 53%. The area under the receiver-operator characteristic curve using dichotomised variables was 0.74 and for continuous model 0.78. CONCLUSIONS: Our prognostic index which uses eight non-invasive measurements and a straightforward additive points system, has good discrimination and stratifies outpatients with chronic heart failure into high and low risk. This index may be useful in clinical care and risk stratification.     

Smoking reduction,smoking cessation,and mortality: a 16-year follow-up of 19,732 men and women from The Copenhagen Centre for Prospective Population Studies

The authors investigated the association between changes in smoking habits and mortality by pooling data from three large cohort studies conducted in Copenhagen, Denmark. The study included a total of 19,732 persons who had been examined between 1967 and 1988, with reexaminations at 5- to 10-year intervals and a mean follow-up of 15.5 years. Date of death and cause of death were obtained by record linkage with nationwide registers. By means of Cox proportional hazards models, heavy smokers (>or=15 cigarettes/day) who reduced their daily tobacco intake by at least 50% without quitting between the first two examinations and participants who quit smoking were compared with persons who continued to smoke heavily. After exclusion of deaths occurring in the first 2 years of follow-up, the authors found the following adjusted hazard ratios for subjects who reduced their smoking: for cardiovascular diseases, hazard ratio (HR) = 1.01 (95% confidence interval (CI): 0.76, 1.35); for respiratory diseases, HR = 1.20 (95% CI: 0.70, 2.07); for tobacco-related cancers, HR = 0.91 (95% CI: 0.63, 1.31); and for all-cause mortality, HR = 1.02 (95% CI: 0.89, 1.17). In subjects who stopped smoking, most estimates were significantly lower than the heavy smokers'. These results suggest that smoking reduction is not associated with a decrease in mortality from tobacco-related diseases. The data confirm that smoking cessation reduces mortality risk.