Application of the Bayesian dynamic survival model in medicine.

The Bayesian dynamic survival model (BDSM), a time-varying coefficient survival model from the Bayesian prospective, was proposed in early 1990s but has not been widely used or discussed. In this paper, we describe the model structure of the BDSM and introduce two estimation approaches for BDSMs: the Markov Chain Monte Carlo (MCMC) approach and the linear Bayesian (LB) method. The MCMC approach estimates model parameters through sampling and is computationally intensive. With the newly developed geoadditive survival models and software BayesX, the BDSM is available for general applications. The LB approach is easier in terms of computations but it requires the prespecification of some unknown smoothing parameters. In a simulation study, we use the LB approach to show the effects of smoothing parameters on the performance of the BDSM and propose an ad hoc method for identifying appropriate values for those parameters. We also demonstrate the performance of the MCMC approach compared with the LB approach and a penalized partial likelihood method available in software R packages. A gastric cancer trial is utilized to illustrate the application of the BDSM.

Effect of treatment and adherence on ethnic differences in blood pressure control among adults with hypertension.

We evaluated whether hypertension control differs by ethnicity after accounting for patient characteristics, treatment, and adherence to treatment using the third National Health and Nutrition Examination Survey (US population estimate, 42,511,379). Outcome measures were prescribed treatment, treatment adherence, hypertension control (blood pressure [BP]<140/90 mm Hg). Multivariate logistic regression was performed with non-Hispanic whites (NHW) as the comparison group. Non-Hispanic blacks (NHB) were more likely to report medication prescription (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.1-2.5) and being advised to restrict salt (OR 1.5, CI: 1.2-2.0). Among those advised, NHB were more likely to report salt restriction (OR 1.5, CI: 1.1-2.1) and weight-loss attempts (OR 1.7, CI: 1.3-2.3). Among persons advised to follow exercise, alcohol restriction, smoking cessation, tension reduction, or diet modification, NHB (OR 2.2, CI: 1.6-3.0) and Mexican Americans (OR 2.0, CI: 1.1-3.9) were more likely to report adherence. The likelihood of uncontrolled hypertension was higher in NHB (OR 1.4, CI: 1.1-1.7) and Mexican Americans (OR 1.5, CI 1.1-2.0) despite medication adherence. Even after adjustment for treatment and adherence, substantial ethnic differences in hypertension control were found. Initiating treatment, while crucial, is not sufficient and future guidelines should emphasize aggressive treatment escalation to achieve hypertension control.

Thirty-year Survival for Black and White Hypertensive Individuals in the Evans County Heart Study and the Hypertension Detection and Follow-up Program.

The Evans County Heart Study (ECHS), initiated in 1960, was one of the first major studies to document cardiovascular disease (CVD) risks for African Americans and Caucasians with elevated blood pressures. In the early 1970's, the Hypertension Detection and Follow-up Program (HDFP), with a site in Georgia (HDFP-GA) was one of the first major studies to demonstrate that treating hypertension with stepped care (SC), versus referred care (RC), has better short-term outcomes. With this background, study objectives were to evaluate 30-year survival and cardiovascular outcomes of the HDFP-GA and to compare outcomes of these patients with 1619 hypertensive individuals (30-69 years of age) from the ECHS. HDFP-GA patients included 688 individuals (black [n=267]; white [n=421]) randomized to RC (n=341) and SC (n=347). The ECHS was comprised of 733 black and 886 white hypertensives. All-cause mortality and CVD mortality were assessed in the HDFP-GA and compared to the ECHS hypertensives. After 30-years of follow-up, 65.7% of the HDFP-GA cohort had died compared with a similar 65.8% of the ECHS hypertensives. However, CVD mortality rates, while similar for the SC and RC arms, were lower than in the HDFP-GA total study group than the hypertensive participants of ECHS (32.6% vs. 40.3% p<.001). CVD survival rates for both SC and RC HDFP-GA arms were significantly better than population-based hypertensive individuals in the ECHS, with consistent benefits in all four race-sex groups. These results identify the importance of long-term follow-up of individuals in hypertension studies and trials that include CVD outcomes.

Protein and legume intake and prostate cancer mortality in Puerto Rican men.

Prostate cancer is the number 1 cancer killer among Puerto Rican (PR) men. Plant foods have been inversely associated with prostate cancer. Legumes play a significant role in the PR diet; consumption of legumes in PR (14 lb/capita) was double that of the United States (7 lb/capita). We examined dietary protein consumption (from baseline 24-h dietary recalls) and prostate cancer mortality in the PR Heart Health Program, a cohort study of 9,824 men aged 35-79 years at baseline (1964) with follow-up until 2005. Total protein intake in the cohort was 85 g/day, and sources of protein were 30% vegetable, 30% dairy, 31% animal, and 8% seafood protein. Legume intake was 2.3 servings/day (1/4 cup each). Legume intake was not associated with prostate cancer mortality [comparing highest quartile to lowest quartile-odds ratio (OR) 1.40 [95% confidence interval (CI) 0.91-2.18], P trend 0.17]-nor were total protein, animal, seafood, dairy, or vegetable protein intakes. Consuming 1-2 servings of fruit was inversely associated (OR 0.50, 95% CI 0.32-0.77), whereas consuming more than 2 servings of fruit was not associated with prostate cancer mortality. Thus, we find no association between legumes or protein intake and prostate cancer mortality in this longitudinal cohort study of PR men.

Sex differences in the effect of diabetes duration on coronary heart disease mortality.

BACKGROUND: It is not known whether the coronary heart disease (CHD) mortality risk associated with recent (RDM; <10 years) or long-standing diabetes mellitus (LDM; > or =10 years) varies by sex. METHODS: The relationship between diabetes duration and CHD mortality was evaluated among 10 871 adults (aged 35-74 years at baseline) using the 1971-1992 National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. RESULTS: The CHD mortality rates per 1000 person-years in men with no myocardial infarction (MI) or diabetes, MI only, RDM only, LDM only, MI and RDM, and MI and LDM were 5.5 (95% confidence interval, 4.8-6.2), 15.2 (11.6-20.0), 13.2 (7.9-22.1), 11.4 (6.4-20.3), 36.0 (16.7-77.7), and 35.4 (14.0-89.7), respectively. The corresponding rates in women were 2.9 (2.5-3.3), 7.3 (5.0-10.8), 5.2 (3.5-7.7), 10.7 (7.5-15.5), 9.3 (4.3-19.9), and 21.6 (6.1-76.0), respectively. Compared with MI, the multivariate hazard ratios and their 95% confidence intervals (adjusted for age, race, smoking, hypertension, total cholesterol level, and body mass index) for fatal CHD in men with RDM, LDM, MI and RDM, and MI and LDM were 0.7 (0.3-1.3), 0.8 (0.4-1.4), 3.2 (1.4-7.4), and 2.4 (0.8-6.7), respectively. The corresponding ratios in women were 0.9 (0.6-1.3), 1.8 (1.1-3.2), 1.3 (0.5-3.5), and 1.6 (0.2-10.9), respectively. CONCLUSIONS: In men, RDM and LDM were associated with as high a risk for CHD death as MI. In women, although RDM had a CHD mortality risk similar to MI, LDM had an even greater risk. Because women with LDM are at very high risk for CHD mortality, current guidelines may need to be further refined to match intensity of treatment to risk in these women.

Body mass index and mortality: a meta-analysis based on person-level data from twenty-six observational studies.

PURPOSE: For this report, we examined the relationships between the conditions of being overweight and obese and mortality from all causes, heart disease, cardiovascular disease, and cancer. METHODS: We defined the categories of body weight according to level of body mass index, BMI=wt(kg)/ht(m)2, using classifications suggested by the National Institutes of Health and the World Health Organization. These classifications are as follows: "normal weight" is defined as BMI > or = 18.5, but less than 25; "overweight" equals BMI > or = 25, but less than 30; and "obese" individuals have BMIs > or = 30. Our investigation is based on person-level data from 26 observational studies that include both genders, several racial and ethnic groups, and samples from the US and other countries. The database consists of 74 analytic cohorts, arranged according to natural strata including gender, race, and area of residence. It includes 388,622 individuals, with 60,374 deaths during follow-up. We use proportional hazards models to examine the relationships between the BMI categories and mortality, controlling for age and smoking status. We use random-effects models to assess summary relative risks associated with the overweight and obesity conditions across cohorts. RESULTS: The relative risks among the heaviest individuals for overall death, death caused by coronary heart disease (CHD), and death caused by cardiovascular disease (CVD) are 1.22, 1.57, and 1.48, respectively, when compared with the those within the lowest BMI category. The summary relative risk among the heaviest participants for death from cancer is 1.07. CONCLUSIONS: We document once again, excess mortality associated with obesity. Our results do, however, question whether the current classification of individuals as "overweight" is optimal in the sense, since there is little evidence of increased risk of mortality in this group.

Sex differences in risk for coronary heart disease mortality associated with diabetes and established coronary heart disease.

BACKGROUND: The sex-specific independent effect of diabetes mellitus and established coronary heart disease (CHD) on subsequent CHD mortality is not known. METHODS: This is an analysis of pooled data (n = 5243) from the Framingham Heart Study and the Framingham Offspring Study with follow-up of 20 years. At baseline (1971-1975), 134 men and 95 women had diabetes, while 222 men and 129 women had CHD. Risk for CHD death was analyzed by proportional hazards models, adjusting for age, hypertension, serum cholesterol levels, smoking, and body mass index. The comparative effect of established CHD vs diabetes on the risk of CHD mortality was tested by testing the difference in log hazards. RESULTS: The adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) for death from CHD were 2.1 (95% CI, 1.3-3.3) in men with diabetes only, and 4.2 (95% CI, 3.2-5.6) in men with CHD only compared with men without diabetes or CHD. The HR for CHD death was 3.8 (95% CI, 2.2-6.6) in women with diabetes, and 1.9 (95% CI, 1.1-3.4) in women with CHD. The difference between the CHD and the diabetes log hazards was +0.73 (95% CI, 0.72-0.75) in men and -0.65 (95% CI, -0.68 to -0.63) in women. CONCLUSIONS: In men, established CHD signifies a higher risk for CHD mortality than diabetes. This is reversed in women, with diabetes being associated with greater risk for CHD mortality. Current treatment recommendations for women with diabetes may need to be more aggressive to match CHD mortality risk.

The relationship of physical activity and body weight with all-cause mortality: results from the Puerto Rico Heart Health Program.

PURPOSE: To study the relationship of physical activity and obesity with all-cause mortality in Puerto Rican Men. METHODS: The Puerto Rico Heart Health Program collected physical activity and anthropometric measurements in 9,824 men between 1962 and 1965. After excluding those with known coronary heart disease at baseline, and those who died within the first three years of the study we analyzed the data for the relationship between physical activity and overweight status to all-cause mortality in 9,136 men. We stratified our participants by quartiles of physical activity. Participants were classified into four categories of body weight: underweight (BMI < 18.5), healthy weight (BMI =18.5-24.9), overweight (BMI = 25-29.9), and obese (BMI = 30+). RESULTS: After adjusting for age, education, smoking status, hypertension status, hypercholesterolemic status, urban/rural residence, and overweight status, physical activity was independently related to all-cause mortality. All-cause mortality was lower in those in quartile 2 (OR = 0.68, CI = 0.58-0.79) than quartile 1 (reference, sedentary group). Mortality among those in quartile 3 and 4 (0.63, CI = 0.54-0.75; and 0.55, CI = 0.46-0.65, respectively) were also significantly lower than those observed in quartile 1, but not significantly lower than those observed in quartile 2. Furthermore, within every category of body weight, those who were most active had significantly lower odds ratio of all-cause mortality. CONCLUSION: Our findings support the current recommendation that some physical activity is better than none, in protecting against all-cause mortality. The benefits of an active lifestyle are independent of body weight and that overweight and obese Puerto Rican men who are physically active experienced significant reductions in all-cause mortality compared with their sedentary counterparts.

Effect of cerclage on obstetrical outcome in twin gestations with a shortened cervical length.

OBJECTIVE: Our purpose was to determine the impact of cerclage placement on obstetric outcome in twin gestations with a shortened cervical length. STUDY DESIGN: A prospective cohort study of 147 consecutive twin pregnancies (July 1994 to March 2001) who underwent transvaginal ultrasonographic cervical length measurement between 18 and 26 weeks' gestation. Cerclage was offered to women with cervical lengths < or = 25 mm. Patients were segregated into quartiles by cervical length. Regression analysis and chi(2) tests were used to determine the effect of cervical length and cerclage on parameters of prematurity. RESULTS: One hundred twenty-eight twin gestations met inclusion criteria, including 21 (16.4%) who underwent cerclage for a cervical length < or = 25 mm. Decreasing cervical length was significantly associated with a shorter length of gestation, lower combined birth weight, delivery at < or = 34 weeks, preterm premature rupture of fetal membranes, and very low birth weight. None of these outcomes was altered by cerclage placement. CONCLUSION: Midtrimester cerclage does not alter the risks of prematurity associated with a shortened cervical length in twin gestations.