Biomedical subjects

T E Raghunathan

Publications and source records attributed to T E Raghunathan.

6 recordsLinked to original sources

PubMed1995

Dietary intake and cell membrane levels of long-chain n-3 polyunsaturated fatty acids and the risk of primary cardiac arrest.

OBJECTIVE: To assess whether the dietary intake of long-chain n-3 polyunsaturated fatty acids from seafood, assessed both directly and indirectly through a biomarker, is associated with a reduced risk of primary cardiac arrest. DESIGN: Population-based case-control study. SETTING: Seattle and suburban King County, Washington. PARTICIPANTS: A total of 334 case patients with primary cardiac arrest, aged 25 to 74 years, attended by paramedics during 1988 to 1994 and 493 population-based control cases and controls, matched for age and sex, randomly identified from the community. All cases and controls were free of prior clinical heart disease, major comorbidity, and use of fish oil supplements. MEASURES OF EXPOSURE: Spouses of case patients and control subjects were interviewed to quantify dietary n-3 polyunsaturated fatty acid intake from seafood during the prior month and other clinical characteristics. Blood specimens from 82 cases (collected in the field) and 108 controls were analyzed to determine red blood cell membrane fatty acid composition, a biomarker of dietary n-3 polyunsaturated fatty acid intake. RESULTS: Compared with no dietary intake of eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3), an intake of 5.5 g of n-3 fatty acids per month (the mean of the third quartile and the equivalent of one fatty fish meal per week) was associated with a 50% reduction in the risk of primary cardiac arrest (odds ratio [OR], 0.5; 95% confidence interval [CI], 0.4 to 0.8), after adjustment for potential confounding factors. Compared with a red blood cell membrane n-3 polyunsaturated fatty acid level of 3.3% of total fatty acids (the mean of the lowest quartile), a red blood cell n-3 polyunsaturated fatty acid level of 5.0% of total fatty acids (the mean of the third quartile) was associated with a 70% reduction in the risk of primary cardiac arrest (OR, 0.3; 95% CI, 0.2 to 0.6). CONCLUSION: Dietary intake of n-3 polyunsaturated fatty acids from seafood is associated with a reduced risk of primary cardiac arrest.

Adult↗

PubMed1995

Including deaths when measuring health status over time.

Measuring health status over time is problematic when some subjects die, because death does not have a defined value on most health status measures. This situation is different from the usual missing data problem because the health status of the dead is, in a sense, known. We examined eight strategies for incorporating deaths into such analyses using three health status measures taken from two data sets, after which we used computer simulation to explore more fully the effect of deaths. The strategies differed in the amount of influence given to the deaths, varying from none (deaths were discarded) to complete (mortality itself was the health measure). The strategies that gave less influence to deaths tended to show more favorable changes in health over time, and therefore, tended to favor the group that had more deaths. The strategies that were more influenced by death showed more negative changes over time and favored the group with fewer deaths. The choice of strategy should depend on the goals of an intervention. For health promotion studies, we recommend recoding the health variables to estimate the probability that a person will be healthy in 2 years (or in some other period that can be estimated from the data).

Aged↗

PubMed1994

Monte Carlo methods for exploring sensitivity to distributional assumptions in a Bayesian analysis of a series of 2 x 2 tables.

This paper develops Monte Carlo methods for a Bayesian analysis of a series of 2 x 2 tables under a variety of distributional assumptions. I assume that the data in each table were generated from a pair of binomial distributions and the logarithm of odds of a favourable response follows a bivariate distribution with means that are linear functions of covariates and an arbitrary covariance matrix. I use Gibbs and importance sampling methods to obtain various characteristics of the posterior distribution of the quantities of interest. I apply the method to analyse the data from a population case-control study. Given the size of the population at risk I also derive the posterior distribution of the risk difference defined as the difference in the probabilities of disease development in the exposed and unexposed groups.

Bayes Theorem↗

PubMed1994

Diuretic therapy for hypertension and the risk of primary cardiac arrest.

BACKGROUND: The results of trials of the primary prevention of coronary heart disease have suggested that treating hypertension with high doses of thiazide diuretic drugs might increase the risk of sudden death from cardiac causes. In contrast, treatment with low doses of thiazide reduces the risk of coronary heart disease. METHODS: To examine the association between thiazide treatment for hypertension and the occurrence of primary cardiac arrest, we conducted a population-based case-control study among enrollees of a health maintenance organization. The case patients were 114 persons with hypertension who had a primary cardiac arrest from 1977 through 1990. The control patients were a stratified random sample of 535 persons with hypertension. The patients' treatment was assessed with the use of a computerized pharmacy data base. Records of their ambulatory care were reviewed to determine other clinical characteristics. RESULTS: The risk of primary cardiac arrest among patients receiving combined thiazide and potassium-sparing diuretic therapy was lower than that among patients treated with a thiazide without potassium-sparing therapy (odds ratio, 0.3; 95 percent confidence interval, 0.1 to 0.7). As compared with low-dose thiazide therapy (25 mg daily), moderate-dose therapy (50 mg daily) was associated with a moderate increase in risk (odds ratio, 1.7; 95 percent confidence interval, 0.7 to 4.5), and high-dose therapy (100 mg daily) was associated with a larger increase in risk (odds ratio, 3.6; 95 percent confidence interval, 1.2 to 10.8) (P value for trend, 0.02). The addition of a potassium-sparing drug to low-dose thiazide therapy was associated with a reduced risk of cardiac arrest (odds ratio, 0.4; 95 percent confidence interval, 0.1 to 1.5). CONCLUSIONS: Both the dose of thiazide drugs and the addition of potassium-sparing drugs influence the risk of primary cardiac arrest. These results may explain the differences in the effect of antihypertensive therapy on mortality from coronary heart disease in previous clinical trials.

Aged↗

PubMed1991

Pooling controls from different studies.

This paper develops a method for estimating the odds ratio in a case-control study that 'borrows' strength from the controls in similar previous studies. We assume that the observations within each stratum in the current study are generated from a pair of independent binomial distributions. We assume that the observations on the controls, again within each stratum and from the previous studies, are independent binomial random variables. We use these controls to construct a prior distribution for the stratum specific log-odds for the controls in the current study which we then combine with the likelihood from the current study to arrive at the posterior distribution of the target quantities of interest, the adjusted or stratum specific log-odds ratios. We assume a diffuse prior distribution for the stratum specific log-odds ratio. A simulation study investigates the frequency or repeated sampling properties of the inference based upon the posterior distribution of the log-odds ratio so constructed.

Bayes Theorem↗

PubMedDate not supplied

The risk of myocardial infarction associated with antihypertensive drug therapies.

OBJECTIVE: To assess the association between first myocardial infarction and the use of antihypertensive agents. DESIGN AND SETTING: We conducted a population-based case-control study among enrollees of the Group Health Cooperative of Puget Sound (GHC). PATIENTS AND METHODS: Cases were hypertensive patients who sustained a first fatal or nonfatal myocardial infarction from 1986 through 1993 among women and from 1989 through 1993 among men. Controls were a stratified random sample of hypertensive GHC enrollees, frequency matched to the cases on age, sex, and calendar year. All 623 cases and 2032 controls had pharmacologically treated hypertension. Data collection included a review of the ambulatory medical record a brief telephone interview of consenting survivors. Antihypertensive therapy was assessed using the GHC's computerized pharmacy database. RESULTS: The first analysis included only the 335 cases and 1395 controls initially free of cardiovascular disease. Compared with users of diuretics alone, the adjusted risk ratio of myocardial infarction was increased by about 60% among users of calcium channel blockers with or without diuretic (risk ratio = 1.62%; 95% confidence interval [Cl], 1.11 to 2.34; P = .01). The second analysis was restricted to 384 cases and 1108 controls who were taking either a calcium channel blocker or a beta-blocker. Among these subjects, the use of calcium channel blockers compared with beta-blockers was associated with about a 60% increase in the adjusted risk of myocardial infarction (risk ratio = 1.57; 95% Cl, 1.21 to 2.04; P < .001). While high doses of beta-blockers were associated with a decreased risk of myocardial infarction (trend P = .04), high doses of calcium channel blockers were associated with an increased risk (trend P < .01). CONCLUSIONS: In this study of hypertensive patients, the use of short-acting calcium channel blockers, especially in high doses, was associated with an increased risk of myocardial infarction. Ongoing large-scale clinical trials will assess the effect of various antihypertensive therapies, including calcium channel blockers, on several important cardiovascular end points. Until these results are available, the findings of this study support the current guidelines from the Joint National Committee on the Detection, Evaluation and Treatment of High Blood Pressure that recommend diuretics and beta-blockers as first-line agents unless contraindicated, unacceptable, or not tolerated.

Adrenergic beta-Antagonists↗