Search PubMed⌕ Search

Biomedical subjects

C E Davis

Publications and source records attributed to C E Davis.

At least 73 records · Page 4Linked to original sources
PubMed1995

An empirical evaluation of the placebo run-in.

A prerandomization placebo run-in period is often used in an attempt to exclude potential clinical trial participants who are likely to be poor adheres. It is assumed that potential participants who are poor adherers during the run-in will be less likely to take medication during the trial. This assumption was tested in the Cholesterol Reduction in Seniors Program (CRISP), by prescribing placebo for a 3-week period, but not using the results of the run-in as an entry criterion. The CRISP study was a pilot study designed to compare the effects on lipids and the safety of two doses of lovastatin and placebo in persons 65 years of age and older. After general entry criteria were satisfied, each participant was prescribed placebo for a 3-week period. At the end of the 3-week period, all participants were randomized to one of the three treatment groups, regardless of their adherence to the placebo. Of the 431 participants in the study, 66 (15%) who took less than 80% of the prescribed placebo or who failed to return their unused placebo pills were classified as poor run-in adherers. Poor run-in adherence was associated with lower educational attainment. At 3 and 6 months of follow-up mean adherence was 89.3% and 83.4% among all participants. Exclusion of poor run-in adherers would have increased these means to 90.9% and 85.5%, respectively. Treatment effect as measured by fall in LDL cholesterol would have increased by 2.9 mg/dl in the 40 mg/day dose group at 3 months of follow-up with the addition of a placebo run-in. We conclude that a placebo run-in would have had little effect on the outcome of the CRISP study and would have substantially increased recruitment difficulties. Lower educated persons were more likely to be excluded by a placebo run-in, but the effect of the run-in on follow-up adherence was stronger in less educated participants. More research about the role of a placebo run-in is needed in order to determine the appropriate role of this method in clinical trials.

Aged↗
PubMed1995

Association of high-density-lipoprotein cholesterol with mortality and other risk factors for major chronic noncommunicable diseases in samples of US and Russian men.

Previous reports from the Russian Lipid Research Clinics (LRC) study showed no association between the level of high-density-lipoprotein (HDL) cholesterol and mortality from coronary heart disease (CHD), while US LRC data indicated a strong negative association between HDL cholesterol and CHD mortality. This report investigated the association of HDL cholesterol and mortality in these same population samples with follow-up extended to 12 years. The association between HDL cholesterol and mortality remained inverse and significant in the US sample. In the Russian sample, high levels of HDL cholesterol were associated with higher risk of all-cause and cancer mortality, although adjustment for known risk factors reduced the strength of the association. The association between HDL cholesterol and CHD mortality was negative in the Russian sample, although the strength of the association was less than that for the US sample. Extended follow-up reduced the difference in the association between HDL cholesterol and mortality between the two countries; however, important differences remained. Further research will be required to clearly determine the cause for their differences.

Adult↗
PubMed1995

Effects of cigarette smoking on lung function in four population samples in the People's Republic of China. The PRC-US Cardiovascular and Cardiopulmonary Epidemiology Research Group.

As part of an ongoing study of cardiopulmonary risk factors in the People's Republic of China, we conducted lung function tests and obtained information about smoking habits on 6,765 Chinese men and women 35 to 56 yr of age residing in or around Beijing in the north and in or around Guangzhou in the south. Within each region, separate urban and rural populations were recruited. This study examined the relationship between tobacco consumption (both manufactured cigarettes and leaf tobacco) and lung function in a subset of current smokers and never smokers who had acceptable lung function data. All methods were strictly standardized. Overall, tobacco smoking was associated with a statistically significant mean difference in FEV1 among men (-89 ml) and women (-52 ml) relative to never smokers after adjusting for age, height, and residence. Differences between smokers of cigarettes and smokers of leaf tobacco were not significant. Among the subset of smokers who smoked only cigarettes, this decrement increased with increasing duration of cigarette smoking, but it was small (-4 ml/yr of smoking for FEV1 for both men and women) in comparison with the effects of smoking reported from western countries. Although the smoking effect tended to increase with increasing dose, these differences were small and generally not statistically significant. The relatively small smoking effect in this study may result from differences between developed and developing countries in the cumulative dose of tobacco products. Alternative explanations or contributing factors such as racial differences in susceptibility and differences in the form and delivery of tobacco cannot be discounted.

Adult↗
PubMed1995

Correlation of specific platelet activation markers with carotid arterial wall thickness.

Many studies have shown increased platelet activation in patients with coronary artery, cerebrovascular and peripheral vascular diseases. However, the temporal relationship between platelet activation and arterial atherosclerosis is unclear. To answer this basic question, we measured the plasma concentrations of two specific platelet activation markers, beta-thromboglobulin (beta TG) and platelet factor 4 (PF4) in 459 cases with increased carotid arterial wall thickness and 459 age-, sex-and race-matched controls selected from a cohort of 15,800 men and women, aged 45-64 who participated in the Atherosclerosis Risk in Communities Study. These participants had no acute vascular symptoms or known cardiovascular disease. The mean values of beta TG and PF4 were significantly higher in cases than in controls. However, when analyzed by quartiles using conditional logistic regression, only beta TG exhibited a significant association with carotid wall thickness, while PF4 did not. The odds ratio (OR) determined by multivariate logistic regression analysis was significantly higher for the uppermost quartile of beta TG (OR=1.7, 95% CI 1.1-2.5) compared to the lower 3 quartiles. This OR was 2.3 in white men (95% CI 1.2-4.2), 1.4 in white women (95% CI 0.6-3.0) and 1.0 in blacks (95% CI 0.4-2.5). This study indicates that plasma beta TG may be useful as a marker for early atherosclerosis in middle aged adults, particularly in white men. It also suggests that platelet activation has an independent role in the pathogenesis of atherosclerosis, although the possibility that this may be a response to carotid atherosclerosis cannot be excluded.

Biomarkers↗
PubMed1994

Serum carotenoids and coronary heart disease. The Lipid Research Clinics Coronary Primary Prevention Trial and Follow-up Study.

OBJECTIVE: To examine the relationship between total serum carotenoid levels and the risk of subsequent coronary heart disease (CHD) events. DESIGN: New analysis of a cohort from the Lipid Research Clinics Coronary Primary Prevention Trial and Follow-up Study (LRC-CPPT). The LRC-CPPT was a multicenter placebo-controlled trial of cholestyramine resin and CHD with a follow-up period of 13 years. Serum carotenoids were measured at baseline. PARTICIPANTS: The placebo group of the LRC-CPPT, which consisted of 1899 men aged 40 to 59 years with type II-a hyperlipidemia and without known preexisting CHD, cancer, or other major illnesses. MAIN OUTCOME MEASURES: Nonfatal myocardial infarctions and deaths attributable to CHD ascertained from hospital records, autopsy reports, and death certificates and reviewed by a panel of cardiologists. RESULTS: After adjustment for known CHD risk factors including smoking, serum carotenoids were inversely related to CHD events. Men in the highest quartile of serum carotenoids had an adjusted relative risk (RR) of 0.64 (95% confidence interval [CI], 0.44 to 0.92) compared with the lowest quartile. For men who never smoked, this RR was 0.28 (95% CI, 0.11 to 0.73). CONCLUSIONS: The LRC-CPPT participants with higher serum carotenoid levels had a decreased risk of incident CHD. This finding was stronger among men who never smoked.

Adult↗
PubMed1994

Lipoprotein(a) levels and risk of coronary heart disease in men. The lipid Research Clinics Coronary Primary Prevention Trial.

OBJECTIVE: To examine the relationship between elevated levels of lipoprotein(a) [Lp(a)] and coronary heart disease (CHD) risk in a prospective study. DESIGN: Nested case-control study. The cohort consisted of participants in the Lipid Research Clinics Coronary Primary Prevention Trial. SETTING: Lipid research clinics. PARTICIPANTS: The Lipid Research Clinics Coronary Primary Prevention Trial participants (n = 3806) were men, aged 35 to 59 years, with plasma cholesterol levels of 6.85 mmol/L (265 mg/dL) or greater, low-density lipoprotein cholesterol levels of 4.91 mmol/L (190 mg/dL) or greater, and triglyceride levels less than 3.39 mmol/L. Subjects were randomly assigned to either cholestyramine or placebo treatment. The Lp(a) levels were measured in plasma samples obtained prior to randomization in 233 cases (participants who developed CHD in the course of the study) and 390 matched CHD-free controls. A total of 96.95% of the subjects were white, 2.25% were black, and 0.80% were of other race. MAIN OUTCOME MEASURE: Coronary heart disease (either fatal or nonfatal) events during a follow-up of 7 to 10 years. RESULTS: The Lp(a) levels were significantly higher (21%) in cases than in controls (23.7 mg/dL [0.59 mmol/L] and 19.5 mg/dL [0.49 mmol/L], respectively; P < .02). This difference was still statistically significant (P < .01) after controlling for age, body mass index, cigarette smoking, blood pressure, low-density lipoprotein cholesterol level, and high-density lipoprotein cholesterol level. When subjects were divided by treatment, both cholestyramine-treated and placebo-treated CHD subjects had Lp(a) levels 20% to 22% greater than their matched controls. However, possibly because of smaller sample sizes, these differences were no longer statistically significant. CONCLUSIONS: Our data are consistent with the concept that an elevated Lp(a) level is an independent risk factor for CHD in hypercholesterolemic white men.

Adult↗
PubMed1994

Cholesterol lowering in the elderly. Results of the Cholesterol Reduction in Seniors Program (CRISP) pilot study.

BACKGROUND: Total and lipoprotein cholesterol levels continue to be predictors of coronary heart disease risk in men and women over 65 years old. Cholesterol-lowering trials, however, while sometimes including such subjects, have not concentrated on this age group. The Cholesterol Reduction in Seniors Program was a five-center pilot study to assess feasibility of recruitment and efficacy of cholesterol lowering in this age group. METHODS: The study was a randomized, double-masked clinical trial with placebo, 20-mg lovastatin, and 40-mg lovastatin arms. Major efforts were made to recruit women and minorities. Participants were followed up for 1 year on a cholesterol-lowering diet plus placebo or study drug. End points were changes in blood lipid levels. Data on other blood chemistry values, as well as quality-of-life measures and coronary heart disease morbidity and mortality, were also collected. RESULTS: Four hundred thirty-one subjects with low-density lipoprotein cholesterol levels greater than 4.1 and less than 5.7 mmol/L (159 and 221 mg/dL) were randomized, of whom 71% were women and 21% were African Americans; the mean age was 71 years. In the 20- and 40-mg lovastatin groups, total cholesterol levels fell 17% and 20%; low-density lipoprotein cholesterol levels fell 24% and 28%; triglyceride levels fell 4.4% and 9.9%, respectively. High-density lipoprotein cholesterol levels rose 7.0% and 9.0%, respectively. No changes were observed in the placebo group. Gender, race, and age did not significantly affect responses. Coronary heart disease morbidity and mortality data were collected but not analyzed for this study. CONCLUSION: Older subjects of both genders and a variety of racial and ethnic groups can be successfully recruited into a cholesterol-lowering trial. Lovastatin has effects similar to those reported in younger subjects in previous controlled trials. There is little advantage to the higher lovastatin daily dose. Side effects were remarkably low in all groups.

Aged↗
PubMed1994

Correlates of mortality in Russian and US women. The Lipid Research Clinics Program.

Associations between selected risk factors and 7-year all-cause mortality were studied in 2,187 Russian women and 2,146 US women who were screened as part of a US-Russian collaborative program. The US women were screened during the period 1972-1976, while the Russian women were screened from 1978 to 1982. Cigarette smoking and elevated systolic blood pressure were associated with increased mortality in both samples. High density lipoprotein (HDL) cholesterol was inversely related to mortality in US women, but there was no association of HDL cholesterol with mortality in Russian women. Prevalent angina and electrocardiographic abnormalities were associated with mortality in both samples, but the relations achieved statistical significance only in the Russian sample. The problems of cigarette smoking and elevated blood pressure should be addressed with public health measures in both countries. The absence of an association between HDL cholesterol and mortality in the Russian sample should be investigated further.

Adult↗
PubMed1994

Generalizing from clinical trials.

Although randomized controlled clinical trials have become the "gold standard" for evaluating new treatments, only a small subset of the population considered for treatment participate in randomized clinical trials. To what extent is it reasonable to generalize beyond the boundaries of a specific clinical trial? This paper argues that several pieces of information are necessary to determine the extent of extrapolation or generalization warranted in a specific clinical trial. The necessary items of information are derived from basic science laboratory studies; animal studies; genetic studies (where applicable); observational, clinical, and epidemiological studies; and other randomized clinical trials in similar settings or with similar treatments. An example from the field of cholesterol reduction is presented.

Adult↗
PubMed1994

Reporting of assignment methods in clinical trials.

A stratified random sample of the reports of 200 clinical trials, conducted in the 1980s, listed in the February 1991 issue of Controlled Clinical Trials, was reviewed. The four strata were small single-center trials (SST), small multicenter trials (SMT), large single-center trials (LST), and large multicenter trials (LMT). The description of the assignment method in the published reports of the results of the trials was classified into four categories: good description (G), provides details; fair description (F), describes some details; poor description (P), only states that randomization was used; and no description (N). The percentage of good and fair descriptions among the four strata were: [Tables: See Text] The proportion of G or F trials is slightly higher in the LST because one third used systematic rather than random assignment, which is easier to describe. Good descriptions usually require only two or three lines of text, and yet the description of the randomization method for most clinical trials is so poor that the reader cannot tell if randomization has been applied properly.

Controlled Clinical Trials as Topic↗
PubMed1994

Black women have smaller abdominal girths than white women of the same relative weight.

Anthropometric measurements were compared in 312 white and 242 black women (mean age 54) who were participants in the Charleston Heart Study. Body mass index (BMI) was greater in black women (27.8 kg/m2) than in white women (24.7 kg/m2) as were body circumferences. However, when the girth measurements were adjusted for BMI, some racial differences were reversed. Age, smoking and BMI-adjusted abdominal girth was smaller in the black women than in the white women (88.9 cm vs 92.2 cm). The ratio of abdomen to midarm circumference was larger in white women than black women (3.24 vs 3.09), and could be interpreted to indicate a less central fat pattern in the black women. This conclusion should be viewed with caution since circumference measurements, though often used in epidemiologic research, do not differentiate between subcutaneous fat and visceral fat.

Abdomen↗
PubMed1994

Natural menopause and cardiovascular disease risk factors. The Poland and US Collaborative Study on Cardiovascular Disease Epidemiology.

Changes in risk factor levels associated with menopause have been reported in many studies in the United States and western Europe, where estrogen replacement therapy and surgical menopause are common. We studied risk factor associations in Polish women, for whom estrogen replacement therapy and surgical menopause are uncommon. The 357 postmenopausal women had higher total cholesterol levels (0.43 mmol/L) and low-density-lipoprotein cholesterol levels (0.36 mmol/L than did the 372 premenopausal women of similar ages. Triglycerides, high-density-lipoprotein cholesterol, body mass index, and blood pressure did not differ by menopausal status. We conclude that natural menopause is associated with higher levels of total and low-density-lipoprotein cholesterol levels. Natural menopause is not associated with large changes in other risk factors in this sample.

Blood Pressure↗
PubMed1994

Cutaneous zygomycosis caused by Saksenaea vasiformis in a diabetic patient.

A 49-year-old woman with diabetes mellitus rapidly developed necrotizing cellulitis with fat necrosis and vasculitis after minor trauma to the right arm. Zygomycosis was diagnosed histologically. The lesion responded to aggressive debridement, amphotericin B, and normalization of blood glucose. Cultures yielded structures characteristic of Saksenaea vasiformis only after transfer to saline agar.

Dermatomycoses↗
PubMed1994

Associations of lipoprotein cholesterols, apolipoproteins A-I and B, and triglycerides with carotid atherosclerosis and coronary heart disease. The Atherosclerosis Risk in Communities (ARIC) Study.

Previous research shows generally greater proportional elevation in apolipoprotein B (apoB) levels than in low-density lipoprotein cholesterol (LDL-C) in coronary heart disease (CHD) case subjects compared with control subjects. The Atherosclerosis Risk in Communities study provided general populations of 7261 men and women free of cardiovascular symptoms for evaluating the associations between intima-media thickening in extracranial carotid arteries measured using ultrasound imaging and fasting plasma LDL-C, high-density lipoprotein cholesterol (HDL-C), apoB, apolipoprotein A-I (apoA-I), triglycerides, and HDL density subfractions. A CHD group was selected for comparison. Lipid factors show approximately linear associations with carotid thickness: positive for LDL-C and plasma apoB and negative for HDL-C and apoA-I levels. Apolipoproteins and HDL density subfractions did not contribute to the association after accounting for LDL-C and HDL-C. Compared with control subjects, persons whose carotid thickness exceeded 0.9 mm had greater proportional elevations in LDL-C than in apoB, whereas HDL-C reductions were small. CHD case subjects showed greater proportional elevations of apoB than LDL-C. Although the lipid profiles associated with asymptomatic carotid wall thickening and stenotic coronary disease are similar, the differences found suggest that LDL-C is the most important lipid factor in earlier stages of atherogenesis, whereas the metabolism of triglyceride-rich lipoproteins and its effects on LDL and HDL may be more relevant to later atherothrombotic processes.

Apolipoprotein A-I↗
PubMed1994

Antithrombin III: associations with age, race, sex and cardiovascular disease risk factors. The Atherosclerosis Risk in Communities (ARIC) Study Investigators.

Antithrombin III (AT III) is a major inhibitor of blood coagulation, and hereditary deficiency is associated with venous thrombotic disease. The Atherosclerosis Risk in Communities (ARIC) Study, a prospective study of 15,800 middle-aged men and women, measured AT III in its baseline examination. AT III levels were significantly higher in women than men, and in blacks than whites. AT III decreased with age in men but increased with age in women. In age- and race-adjusted analyses, AT III was positively associated with smoking, HDL-cholesterol, triglycerides (men only), and in women, with diabetes and lipoprotein(a). AT III was negatively associated with educational level, body mass index in men, and use of female hormones in women. Most of these associations were confirmed in multivariate analysis. These correlations between AT III and other risk factors must be considered when evaluating AT III as a risk factor for venous or arterial thrombosis.

Age Factors↗
PubMed1993

Correlation of plasma protein C levels with cardiovascular risk factors in middle-aged adults: the Atherosclerosis Risk in Communities (ARIC) Study.

To evaluate the association of plasma protein C levels with constitutional, socioeconomic, life-style and biochemical factors important in cardiovascular diseases, we measured protein C levels in 12,290 middle aged (45-64 years) subjects participating in the ARIC study. Protein C levels had a normal distribution with a mean value of 3.17 micrograms/ml. They were higher in women than men and in whites than blacks; higher in postmenopausal women and further increased by hormonal supplements. The age influence was inconsistent and was considered to be inconsequential. Protein C levels were positively correlated with body mass index, LDL-cholesterol, HDL-cholesterol, and triglycerides and negatively associated with cigarette smoking. These factors should be taken into consideration when establishing normal protein C levels and when analyzing the relation between protein C and arterial and venous thrombotic disorders.

Age Factors↗
PubMed1993

Value of molecular epidemiologic analysis in a nosocomial methicillin-resistant Staphylococcus aureus outbreak.

OBJECTIVE: To evaluate two molecular epidemiologic methods used in the analysis of a nosocomial methicillin-resistant Staphylococcus aureus (MRSA) outbreak. DESIGN: Restriction endonuclease analysis of plasmid DNA (REAP) was used in the analysis of 45 MRSA isolates. After termination of the outbreak, isolates were retrospectively analyzed in a blind fashion using the newly described technique of arbitrarily primed polymerase chain reaction (AP-PCR). Molecular analyses were compared with epidemiologic and antimicrobial susceptibility data. SETTING: Tertiary care university hospital. SUBJECTS: Twenty-eight patients and 12 employees infected or colonized with MRSA during a 6-week period. RESULTS: A clonal relationship demonstrated among isolates from burn unit patients and staff was clearly distinguishable from MRSA isolates arising from other hospital wards. The combination of REAP and AP-PCR provided complementary information in several instances. Aggressive measures to isolate infected patients and eradicate colonization from patients and staff terminated the outbreak. CONCLUSIONS: Although traditional epidemiologic methods retain their central role in modern hospital infection control, molecular epidemiologic analysis can significantly enhance the ability of infection control officers to analyze and terminate hospital epidemics. The combination of AP-PCR and REAP may prove to be a particularly informative means of tracking the nosocomial spread of microbial strains and their mobile genetic elements.

Adolescent↗