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M Maclure

Publications and source records attributed to M Maclure.

At least 55 records · Page 3Linked to original sources
PubMed1992

Increased onset of sudden cardiac death in the first three hours after awakening.

A circadian variation of sudden cardiac death has been documented, but its relation to individual time of awakening and possible triggering events has not been studied in the general population. By monitoring of mortality records in 4 cities and towns in Massachusetts, 148 potential cases of sudden cardiac death were identified. In 94 cases, the informants listed on the death certificates were contacted, the diagnosis of sudden cardiac death was established, and a telephone interview was completed within a mean of 19 days (range 8 to 28) after the death. The time of day of all 94 cases of sudden cardiac death (mean age 61 +/- 9 years, 74% men) demonstrated a circadian variation (p less than 0.05) with a peak from 9:00 A.M. to 12:00 noon. An analysis of time of death adjusted for individual wake-times of the decedents demonstrated an increased onset of sudden cardiac death during the initial 3-hour interval after awakening with a relative risk of 2.6 (95% confidence interval 1.6, 4.2) compared with other times of the day. The increased risk of sudden cardiac death soon after awakening suggests specific triggering factors or mechanisms that are particularly likely to occur during this time. The narrowing of the time interval during which the risk of sudden cardiac death is increased should facilitate the study of possible pathogenetic mechanisms and triggering factors of the disease and may aid in the design of more effective preventive strategies.

Aged↗
PubMed1992

Tests for trend and dose response: misinterpretations and alternatives.

Tests for overall trend, such as the Mantel extension test, are not tests for monotonic dose response. A survey of epidemiologic articles shows widespread misinterpretation of the Mantel extension test and overstatement of evidence for monotonic dose response when there are few exposed subjects. To properly evaluate the hypothesis that risk continues to increase with further increases in exposure, one must examine several statistics and estimates. Given sufficient data, nonparametric or polynomial regression analyses can provide more detailed dose-response information.

Epidemiologic Methods↗
PubMed1991

The case-crossover design: a method for studying transient effects on the risk of acute events.

A case-control design involving only cases may be used when brief exposure causes a transient change in risk of a rare acute-onset disease. The design resembles a retrospective nonrandomized crossover study but differs in having only a sample of the base population-time. The average incidence rate ratio for a hypothesized effect period following the exposure is estimable using the Mantel-Haenszel estimator. The duration of the effect period is assumed to be that which maximizes the rate ratio estimate. Self-matching of cases eliminates the threat of control-selection bias and increases efficiency. Pilot data from a study of myocardial infarction onset illustrate the control of within-individual confounding due to temporal association of exposures.

Bias↗
PubMed1991

Taxonomic axes of epidemiologic study designs: a refutationist perspective.

Overlap among the axes of study design used for classifying epidemiologic research creates a taxonomic problem, the complexity of which may be illustrated by Venn diagrams. The diagrams also suggest a solution: to rank axes according to their bearing on study validity. This is consistent with the refutationist criterion for distinguishing strong from weak science--the potential to refute alternative explanations. In epidemiology, this means refuting confounding, reverse-causation bias, selection or allocation bias, and misclassification bias. Using susceptibility to bias as a criterion for ranking axes, a simple taxonomy emerges that is compatible with widespread usage of terminology.

Bias↗
PubMed1991

A prospective cohort study of nutrient intake and age at menarche.

A cohort of 213 girls (aged 10 y, range +/- 9 mo) whose parents reported their dietary intakes (including nutritional supplements) using a semiquantitative food frequency questionnaire, was followed for 4 y until 82% of the 194 parents who responded to follow-up letters had reported that their daughters had had their first menstrual periods. The relative risk (RR) of menarche before age 12.5 y was 2.0 [95% confidence interval (CI) = 1.1-3.8] for the tallest girls (greater than 150 cm) compared with the shortest girls (less than 130 cm). The RR was 2.1 (95% CI = 1.1-3.8) for the fattest girls [Quetelet's index of relative weight (in kg/m2) greater than 19] vs the leanest girls (less than 15). After adjusting for height and Quetelet's index, menarcheal age was not associated with intake of energy nor energy-adjusted intake of protein, fat, or carbohydrate. The overall results are consistent with the hypothesis that nutritional factors influence age at menarche mainly through their effects on accumulation of adipose tissue.

Age Factors↗
PubMed1990

Analysis of possible triggers of acute myocardial infarction (the MILIS study).

Recent documentation of a circadian variation in acute myocardial infarction (AMI) suggests that AMI is not a random event, but may frequently result from identifiable triggering activities. The possible triggers reported by 849 patients enrolled in the Multicenter Investigation of Limitation of Infarct Size were analyzed. Possible triggers were identified by 48.5% of the population; the most common were emotional upset (18.4%) and moderate physical activity (14.1%). Multiple possible triggers were reported by 13% of the population. Younger patients, men and those without diabetes mellitus were more likely to report a possible trigger than were older patients, women and those with diabetes. The likelihood of reporting a trigger was not affected by infarct size. This study suggests that potentially identifiable triggers may play an important role in AMI. Because potential triggering activities are common in persons with coronary artery disease, yet infrequently result in AMI, further studies are needed to identify (1) the circumstances in which a potential trigger may cause an event, (2) the specific nature of potential triggering activites, (3) the frequency of such activities in individuals who do not develop AMI and (4) the presence or absence of identifiable triggers in various subgroups of patients with infarction.

Aged↗
PubMed1990

Decline of the hemoglobin adduct of 4-aminobiphenyl during withdrawal from smoking.

The hemoglobin adduct of the human bladder carcinogen 4-aminobiphenyl (4ABP-Hb) declined in the blood of 34 smokers enrolled in a withdrawal program, from a mean of 120 +/- 7 (SE) pg/g of hemoglobin at the start to a mean of 82 +/- 6 pg/g after 3 weeks and a mean of 34 +/- 5 pg/g among the 15 exsmokers who had not resumed smoking after 2 months. Although 4ABP-Hb declined faster than expected under the assumption that the human erythrocyte has a life span of 120 days, it persisted much longer than cotinine. Therefore, 4ABP-Hb may complement the use of cotinine as a marker of exposure to tobacco smoke. The strength of the within-person association of 4ABP-Hb with smoking, coupled with the weakness of the between-person association (correlation coefficient, 0.33), is evidence that between-person variation in modifying factors is substantial. Study of the modifiers of 4ABP-Hb levels may help elucidate the etiology of human susceptibility to aromatic amine-induced bladder cancer.

Adult↗
PubMed1990

Multivariate refutation of aetiological hypotheses in non-experimental epidemiology.

Extension of Karl Popper's logic of refutation from the realm of contingency tables to multivariate modelling leads to the conclusion that rigorously scientific multivariate analysis in non-experimental epidemiology differs from the traditional quasi-scientific approach. Instead of aiming for high sensitivity in detecting aetiological agents, the goal in refutation is high specificity--to give the best defence of the 'innocence' of every exposure hypothesized as being a cause. Instead of 'forward selection' or 'backward elimination', multivariate refutation uses the method of 'forward elimination'. This entails a likelihood approach (which may be complemented by, but should be demarcated from, Bayesian methods) not only for statistical inference but also, by analogy, for study design and conduct: one starts with the conclusion (the estimate or hypothesis) and works backwards to the observations (the likelihood of the data or the design of the study). Differences in practice can sometimes be large, as illustrated by a study of hypothesized triggers of myocardial infarction. Multivariate refutation should replace the concept of multivariate modelling in non-experimental epidemiology.

Bayes Theorem↗
PubMed1990

A case-control study of diet and risk of renal adenocarcinoma.

We examined dietary and other risk factors for renal adenocarcinoma in a case-control study of 203 incident and 207 prevalent cases and 605 neighborhood controls. Using unconditional logistic regression to control selection biases identified in an adjunct study, we found exposure odds ratios (OR) similar to those from other studies: 1.9 (with a 95% confidence interval (Cl) from 0.8 to 4.4) for smoking 2 packs of cigarettes per day; 3.8 (95% Cl: 0.78-18) for 3 or more packs per day; 1.7 (95% Cl: 0.9-3.2) for women and 1.7 (95% Cl: 1.1-2.8) for men in the highest quintile of relative weight (kg/m2); 2.0 (95% Cl: 1.3-3.1) for northeastern European ancestry; and 2.3 (95% Cl: 1.3-4.1) for history of kidney stones. Incident cases consumed more meats and fewer vegetables than controls: the age-sex-education-adjusted OR for average intake of 85 g (3 oz) of beef per day was 3.4 (95% Cl: 1.6-7.2). Inverse associations were seen for most vegetables. Dietary animal protein, animal fat, and saturated fat, with and without energy adjustment, were weakly associated with disease in unconditional and conditional logistic regressions. Prior hypotheses concerning intake of cholesterol, beta-carotene, preformed vitamin A, and cruciferous vegetables were not corroborated.

Adenocarcinoma↗
PubMed1990

Analysis of selection bias in a case-control study of renal adenocarcinoma.

Crude estimation of the selection probability ratio (SPR), described previously, was extended to stratified and multivariate estimation and used to assess selection bias in a case-control study of renal adenocarcinoma. It was shown that the directly pooled estimate of the SPR, using the same weights as the directly pooled estimate of the exposure odds ratio (OR) from the case-control study (assuming the OR and SPR are common to all strata and data are abundant), can be multiplied with the OR to yield an adjusted OR that is free from selection bias. Medical records of 548 interviewed cases were compared with 640 noninterviewed cases, and interviews of 640 controls were compared with mailed questionnaires from 272 (60%) of the noninterviewed controls. Age-sex-adjusted point estimates of SPRs ranged from 0.65 to 1.4. Multivariate estimates from binomial regression ranged from 0.34 to 2.0. Higher socioeconomic status and history of renal stones were predictors of participation by both cases and controls. Obesity in women, hypertension, and nonsmoking were predictors in cases only. Heart disease was associated with control participation and case nonparticipation. This study cast doubt on the OR for obesity in women and hypertension in the case-control risk analysis.

Adenocarcinoma↗
PubMed1989

Elevated blood levels of carcinogens in passive smokers.

The hypothesis that involuntary exposure to tobacco smoke--passive smoking--results in greater risk of cancer was assessed by measuring the levels of two known carcinogens in the blood of 57 nonsmokers with varying degrees of involuntary exposure, including six heavily exposed bartenders. The concentrations of hemoglobin adducts of 4-aminobiphenyl, a bladder carcinogen, were significantly higher in subjects with confirmed involuntary exposure (plasma cotinine concentrations between 2 and 23 ng/ml) compared with subjects with undetectable levels of cotinine. Similarly, adducts of 3-aminobiphenyl were significantly elevated in subjects with confirmed exposure. The odds of 3-aminobiphenyl adduct levels exceeding 2 pg/g of hemoglobin were 6:7 among the confirmed exposed, compared with the odds of 2:42 among subjects with undetectable cotinine (odds ratio = 18; 95 percent confidence interval = 3.3, 94). The validity of the assay was demonstrated by showing striking declines in adduct levels among quitting smokers.

Adult↗
PubMed1987

Hemoglobin adducts of 4-aminobiphenyl in smokers and nonsmokers.

A quantitative method has been developed for the analysis of 4-aminobiphenyl (4-ABP) covalently bound as the sulfinic acid amide to the 93 beta cysteine of human hemoglobin. The method uses mild basic hydrolysis of hemoglobin to release the parent amine, derivatization to form the pentafluoropropionamide, and capillary gas chromatography with detection by negative-ion chemical ionization mass spectrometry. The method is precise and gives reproducible results on multiple blood samples taken from individuals over 48 h. Application of this method to blood samples from cigarette smokers and nonsmokers revealed consistently higher adduct levels in smokers. The mean value for smokers was 154 pg 4-ABP per g Hb compared to 28 pg/g Hb for nonsmokers, with no overlap of adduct levels between the two groups. Studies on quitting smokers revealed that adduct levels declined over a period of 6-8 weeks to nonsmoker levels. The finding of 4-ABP adducts in all nonsmokers was not anticipated but is consistent with low-level ubiquitous contamination of air, food, or water. In other animals sampled, rats and dogs had measurable adduct levels, but monkeys and fish did not. The hemoglobin adduct of 4-ABP is the product of a series of reactions between the hemoprotein and N-hydroxy-4-ABP. The formation of hydroxylamines from carcinogenic aromatic amines and their subsequent reactions with DNA are generally thought to be critical events in the initiation of bladder tumors. We suggest that the observed hemoglobin adduct levels formed by this proximate carcinogen will reflect the extent to which these steps have occurred. This is the first report of 4-ABP adducts in human blood.

Aminobiphenyl Compounds↗
PubMed1987

Relative activity of unsaturated fatty acid metabolic pathways in humans.

The four families of unsaturated fatty acids (w9, w7, w6, w3) appear to be elongated and desaturated by enzymes shared among all families. The order of relative pathway activity is hypothesized to be w3 greater than w6 greater than w9 greater than w7. In order to examine this question, we measured by high resolution capillary column gas-liquid chromatography, the relative concentrations of the various fatty acids in plasma from 20 healthy reference subjects, 33 randomly selected subjects from the Framingham Heart Study, and six patients with intestinal malabsorption and suspected severe essential fatty acid deficiency (SEFAD). The ratios of the concentrations of daughter (derivative) fatty acids (DFA) to parent (precursor) fatty acids (PFA) within each family was found to reflect the hypothesized pathway activity. DFA/PFA ratios were 10 to 20 times greater for w3 than for w6 fatty acids (P less than .01), and 5 to 10 times greater for w6 than w9 fatty acids (P less than .01). Patients with SEFAD had lower levels of w3 and w6 fatty acids than the other two groups (P less than .01), higher DFA/PFA in each family (P less than .01), and increased production of both PFA9 and DFA9, consistent with a previously shown shift towards production of w9 fatty acids and with regulation of the pathways by their end products. We also examined the rate of restoration of levels of DFA in the w3 and w6 families in a SEFAD patient intravenously fed soybean oil (55% linoleic acid and 8% linolenic acid). Levels of DFA3s were restored faster than levels of DFA6s, indicating higher w3 pathway activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Asbestos and renal adenocarcinoma: a case-control study.

A case-control study of renal adenocarcinoma has corroborated the hypothesis that asbestos is a cause of the disease. The odds of having been moderately or heavily exposed to asbestos 30 years before diagnosis were 45:473 among cases, whereas the comparable odds among controls were 26:492. A matched-pair analysis yielded an exposure odds ratio of 1.8 with 95% confidence limits of 1.1 and 3.1. After controlling for potential confounders and selection factors by means of logistic regression, the incidence rate ratio was estimated to be 1.6, with a one-sided 95% confidence limit of 1.0.

Adenocarcinoma↗