PubMed Health⌕ Search

Biomedical subjects

M G Larson

Publications and source records attributed to M G Larson.

115 records · Page 7Linked to original sources
PubMed1984

Covariate analysis of competing-risks data with log-linear models.

A general system of log-linear modeling is proposed for analysis of competing-risks data with discrete covariates. The instantaneous cause-specific failure rates, approximated by step-functions, are analyzed by techniques for multidimensional contingency tables. Censored observations are accommodated. Counts of failures of each type, and the amount of follow-up, are summarized in two arrays in which each cell denotes a distinct combination of failure type, time interval and covariate value. Maximum likelihood estimators for the parameters of the model are derived by iterative proportional fitting; the resulting estimates of the number of failures in each cell are used for goodness-of-fit tests. The principal advantages of this approach are its simple display of data, its computational ease for the fitting and comparison of models and its provision of explicit goodness-of-fit tests. Interpretation of the models is facilitated by reference to several alternative models for survivorship and competing risks. The basic model is extended to incorporate stochastic covariates whose values change during follow-up, and to accommodate quantitative covariates.

Analysis of Variance↗
PubMed1983

Measuring function and health status in rheumatic disease clinical trials.

We have summarized the limitations of traditional outcome measures in rheumatology, reviewed the growing field of measures emphasizing the patient's perception of improvement, and provided guidelines for choosing a specific instrument for a clinical trial. Newer measures have measurement properties equal to or surpassing traditional measures, but no one ADL or quality-of-life instrument can be used to assess outcome in every situation as no one test can indicate success of a treatment in a chronic disease. An instrument needs to be judged by the following criteria: Is it metrically sound? Does it fit the socio-demographic characteristics of the target population? Does it measure the specific changes which are likely to be affected by the treatment? Will it capture or measure the expected changes?

Arthritis, Rheumatoid↗
PubMedDate not supplied

Prevalence and correlates of elevated serum creatinine levels: the Framingham Heart Study.

BACKGROUND: Elevated serum creatinine (SCr) levels are a predictor of end-stage renal disease, but little is known about the prevalence of elevated SCr levels and their correlates in the community. METHODS: In this cross-sectional, community-based sample, SCr levels were measured in 6233 adults (mean age, 54 years; 54% women) who composed the "broad sample" of this investigation. A subset, consisting of 3241 individuals who were free of known renal disease, cardiovascular disease, hypertension, and diabetes, constituted the healthy reference sample. In this latter sample, sex-specific 95th percentiles for SCr levels (men, 136 micromol/L [1.5 mg/dL]; women, 120 micromol/L [1.4 mg/dL]) were labeled cutpoints. These cutpoints were applied to the broad sample in a logistic regression model to identify prevalence and correlates of elevated SCr levels. RESULTS: The prevalence of elevated SCr levels was 8.9% in men and 8.0% in women. Logistic regression in men identified age, treatment for hypertension (odds ratio [OR], 1.75; 95% confidence interval [CI], 1.27-2.42), and body mass index (OR, 1.08; 95% CI, 1.01-1.15) as correlates of elevated SCr levels. Additionally, men with diabetes who were receiving antihypertensive medication were more likely to have raised SCr values (OR, 2.94; 95% CI, 1.60-5.39). In women, age, use of cardiac medications (OR, 1.58; 95% CI, 1.10-2.96), and treatment for hypertension (OR, 1.42; 95% CI, 1.07-1.87) were associated with elevated SCr levels. CONCLUSIONS: Elevated SCr levels are common in the community and are strongly associated with older age, treatment for hypertension, and diabetes. Longitudinal studies are warranted to determine the clinical outcomes of individuals with elevated levels of SCr and to examine factors related to the progression of renal disease in the community.

Adult↗
PubMedDate not supplied

Echocardiographic reference values for aortic root size: the Framingham Heart Study.

The objectives of this study were to develop sex-, age-, and body size-specific nomograms and partition values for upper and lower limits of M-mode echocardiographic aortic root measurements derived from a large population-based cohort. The study sample consisted of 1433 male and 1816 female participants in the Framingham Heart Study and Framingham Offspring Study who were normotensive and free of clinically apparent heart disease at the baseline examination. Aortic root measurements were obtained by M-mode echocardiography by a leading-edge to leading-edge technique. The relations of age and measures of body size with aortic root dimensions were evaluated with sex-specific correlations and multiple stepwise linear regression analyses. Age was the most important determinant of aortic root size in both men and women in the multivariable regression models. Models with age and body surface area yielded R2 values of 0.214 in men and 0.222 in women. Models with age and height yielded lower R2 values of 0.136 in men and 0.181 in women. Thus aortic root dimensions vary widely with the age, sex, and body size of individuals. Sex-specific reference nomograms of aortic root dimensions in relation to age and body size (body surface area or height) are presented to facilitate the detection of abnormalities of aortic root size.

Adult↗
PubMedDate not supplied

Reference values for Doppler indexes of left ventricular diastolic filling in the elderly.

Congestive heart failure increases in prevalence with age. A large number of elderly subjects with heart failure have either normal or slightly reduced left ventricular (LV) systolic function; their symptoms are due to diastolic LV dysfunction. Reference values for Doppler indexes of LV diastolic filling in a large sample of the very elderly (> 70) have not been reported previously. The objective of this study was to generate reference values for Doppler indexes of LV filling in a population of apparently healthy elderly men and women. A total of 1201 surviving original subjects of the Framingham Heart Study were evaluated by Doppler echocardiography. A subset of 114 rigorously selected healthy subjects (26 men and 88 women) aged 70 to 87 years (mean 76) constituted the study group. Measurements of seven commonly used Doppler indexes were obtained. Mean and 2.5, 5, 10, 25, 50, 75, 90, 95, and 97.5 percentile values for Doppler diastolic indexes were generated. Stepwise regression analyses were performed to determine the relation of diastolic LV filling to age group (70 to 74 years, 75 to 79 years, and 80 years and over), sex, and other clinical variables. Reference values for the various Doppler parameters were generated on the basis of this healthy elderly cohort. There was evidence for a slight progressive decline in indexes of LV inflow with age. In 87% of this elderly population the ratio of peak early to late velocities of LV diastolic inflow was less than 1.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMedDate not supplied

The progression from hypertension to congestive heart failure.

OBJECTIVES: - To study the relative and population-attributable risks of hypertension for the development of congestive heart failure (CHF), to assess the time course of progression from hypertension to CHF, and to identify risk factors that contribute to the development of overt heart failure in hypertensive subjects. DESIGN: - Inception cohort study. SETTING: - General community. PARTICIPANTS: - Original Framingham Heart Study and Framingham Offspring Study participants aged 40 to 89 years and free of CHF. To reflect more contemporary experience, the starting point of this study was January 1, 1970. EXPOSURE MEASURES: - Hypertension (blood pressure of at least 140 mm Hg systolic or 90 mm Hg diastolic or current use of medications for treatment of high blood pressure) and other potential CHF risk factors were assessed at periodic clinic examinations. OUTCOME MEASURE: - The development of CHF. RESULTS: - A total of 5143 eligible subjects contributed 72422 person-years of observation. During up to 20.1 years of follow-up (mean, 14.1 years), there were 392 new cases of heart failure; in 91% (357/392), hypertension antedated the development of heart failure. Adjusting for age and heart failure risk factors in proportional hazards regression models, the hazard for developing heart failure in hypertensive compared with normotensive subjects was about 2-fold in men and 3-fold in women. Multivariable analyses revealed that hypertension had a high population-attributable risk for CHF, accounting for 39% of cases in men and 59% in women. Among hypertensive subjects, myocardial infarction, diabetes, left ventricular hypertrophy, and valvular heart disease were predictive of increased risk for CHF in both sexes. Survival following the onset of hypertensive CHF was bleak; only 24% of men and 31% of women survived 5 years. CONCLUSIONS: - Hypertension was the most common risk factor for CHF, and it contributed a large proportion of heart failure cases in this population-based sample. Preventive strategies directed toward earlier and more aggressive blood pressure control are likely to offer the greatest promise for reducing the incidence of CHF and its associated mortality.

Adult↗