Olfactory sensitivity in twins.
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Biomedical subjects
Publications and source records attributed to R R Fabsitz.
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Olfactory sensitivity to acetic acid, isobutyric acid, and 2-sec-butyl-cyclohexanone was tested in 97 adult male twin pairs to determine the extent to which variation in odor perception was genetically determined. Analysis of the data revealed no evidence for heritability of olfactory sensitivity. However, factors significantly associated with odor perception included cigar, pipe, and cigarette smoking; body fatness; alcohol consumption; and diabetes mellitus.
In the NHLI Twin Study MZ twins are shown to "get together" substantially more often than DZ twins. With this result as an indicator of differences in shared environment, the assumption of equal shared environmental variation for MZ and DZ twins is assessed using nutritional data calculated from a food frequency questionnaire. Six nutrients show significant genetic variance for the total sample. However, when stratified on the basis of how frequently twins see each other, none of the nutrients shows significant genetic variance for both strata. A similar pattern is seen for several individual items from the questionnaire. In addition, four of the nutrients show significant correlation between the absolute difference in the nutrient intake of MZ twin pairs and how often they "get together." These data appear to show that unequal environmental effects may lead to falsely high estimates of genetic variance for nutrient intake.
Mortality trends from 1950 to 1970 were studied for 473 cities in the United States with populations of 25,000 or more in 1950, according to fluoridation status of their water supplies. Findings showed no relationship between fluoridation and observed changes in general mortality over the 20-year period. Also, no relationship was found between fluoridation and heart or cancer death rate trends.
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Fasting plasma triglycerides and cholesterol, as well as cholesterol in very low density, low density and high density lipoproteins, were measured in 250 MZ and 264 DZ adult male twin pairs. A new method was used to choose an estimate of genetic variance. This includes an estimate of genetic variance for use when the total variances of MZ and DZ twins are unequal. DZ twins had greater total variance for cholesterol. When genetic variance was estimated by subtracting the within-MZ-sets mean square from the within-DZ-sets mean square, all of the lipids had significant estimates of genetic variance; however, when genetic variance was estimated by a method designed to correct bias due to unequal total variances of MZ and DZ twins, only triglycerides had significant genetic variance. The heritability of plasma triglycerides was calculated to be 0.68.
Prehospital delay is considered to be an important cause of out-of-hospital coronary mortality. Behavior of patients and physicians in response to the symptoms of myocardial infarction (MI) or impending out-of-hospital death (OHD) was studied for 107 consecutive acute coronary events in Framingham, Mass. Delay due to inappropriate patient behavior was the most important component of total delay. Delay related to patient-physician contact occurred in two thirds of MI cases and was more than 30 minutes in half of these. Office visits and inappropriate triage by nurses and receptionists were important factors in physician delay. However, 60% to 75% of OHDs occur so rapidly that their prevention by reduction of prehospital delay seems impossible. A strategy for reduction of delay that might be of benefit in preventing some of the remaining OHDs is described.
The Framingham Cardiovascular Disease Survey was undertaken to test the hypothesis that a short-term surveillance study of a defined population could yield incidence data comparable to those obtained by an elaborate longitudinal study of the same population, at a fraction of the cost. New cases of coronary heart disease (CHD), congestive heart failure (CHF) and stroke occurring from June 15, 1970 through June 14, 1971, were detected by monitoring admissions to hospitals and nursing homes, reporting of new events by local physicians and perusal of death certificates, Necessary data on each case were collected and reviewed by a panel of physicians using strict diagnostic criteria. Incidence rates based on 332 CHD or CHF events were calculated and were found to be consistent with findings of the Framingham Heart Study. A one-year community surveillance study is an economical and reasonably accurate method of determining the incidence of CHD and CHF.
Maximal grip strength was measured in kilograms using a hand dynamometer on 344 unrelated males between the ages of 59 and 70 participating in the third examination of the NHLBI Twin Study. There was a significant linear decline in mean grip strength over this age range. Mean grip strength and grip strength per kilogram weight are presented for age 59, ages 60-64 and 65-69. Genetic analysis using 127 pairs of identical (MZ) twins and 130 pairs of fraternal (DZ) twins indicated significant genetic effects for absolute grip strength and grip strength per kilogram weight. The largest estimate of heritability (65%) was obtained for grip strength adjusted for significant effects of weight, height, age, and various anthropometric measures of fatness, muscle mass, and frame size.
BACKGROUND: Both a prolonged QT interval and increased QT interval dispersion (QTD) have been proposed as surface ECG markers of vulnerability to ventricular arrhythmias and potential predictors of mortality. METHODS AND RESULTS: The predictive values of QT prolongation and QTD were assessed in 1839 participants in the Strong Heart Study, a prospective study of cardiovascular disease in American Indians. ECGs were acquired at 250 Hz; QT intervals were measured by computer in all 12 leads and corrected for heart rate (QTc) by use of Bazett's formula. QTD was calculated as the difference between the maximum and minimum QTc. After a mean follow-up of 3.7+/-0.9 years, there were 188 deaths from all causes, including 55 cardiovascular deaths. In univariate Cox analyses, prolonged QTc and increased QTD were significant predictors of all-cause mortality (chi(2)=53.0, P<0.0001; chi(2)=11.3, P=0.0008) and cardiovascular mortality (chi(2)=14.7, P=0.0001; chi(2)=26.5, P<0.0001). In multivariate Cox regression analyses controlling for risk factors, QTc remained a strong predictor of all-cause mortality (chi(2)=16.5, P<0.0001) and a weaker predictor of cardiovascular mortality (chi(2)=5.8, P=0.016); QTD remained a significant predictor of cardiovascular mortality only (chi(2)=12.5, P=0.0004). CONCLUSIONS: These findings support the value of computerized measurements of QTc and QTD in noninvasive risk stratification and suggest that these surface ECG variables may reflect different underlying abnormalities of ventricular repolarization.
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