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Biomedical subjects

G S Omenn

Publications and source records attributed to G S Omenn.

At least 19 recordsLinked to original sources
PubMed1992

Restricted activity days among older adults.

OBJECTIVES: The number of restricted activity days experienced by an individual in the course of a year is an important measure of functional well-being, particularly for older adults. We sought to determine multivariate associations between restricted activity days and various health conditions. METHODS: We used data from the 1984 Supplement on Aging of the National Health Interview Survey to estimate the relationship between restricted activity days and age, gender, and the presence or absence of selected chronic conditions and falls for all noninstitutionalized people aged 65 years and over. Chronic conditions and falls accounted for most of the variance in the model. RESULTS: Of an annual average of 31 restricted activity days, 6 days were associated with falls; 4 days with heart disease; 4 days with arthritis and rheumatism; 2 days each with high blood pressure, cerebrovascular disease, and visual impairment; and 1 day each with atherosclerosis, diabetes, major malignancies, and osteoporosis. CONCLUSIONS: These results can be used in estimating the potential impact of health promotion programs on the health status of noninstitutionalized older adults.

Accidental Falls↗
PubMed1992

Older adults and smoking.

This review supports the following conclusions regarding the benefits of smoking cessation in older adults: 1. Older smokers who quit have a reduced risk of death compared with current smokers within 1 to 2 years after quitting. Their overall risk of death approaches that of those who never smoked after 15 to 20 years of abstinence. 2. Smoking cessation in older adults markedly reduces the risks of coronary events and of cardiac deaths within 1 year of quitting, and risk continues to decline more gradually for many years. This is true for older adults both with and without a previous history of coronary disease and symptoms. 3. Risks of dying from several smoking-related cancers are reduced by quitting. Although the decline in risk may be more gradual for older than middle-aged adults, the benefits of cessation are apparent within 5 to 10 years of quitting. 4. Smoking cessation reduces the risk of COPD mortality after 10 to 15 years of abstinence in men and 5 to 10 years of abstinence in women. Within a shorter period of time, quitting reduces the prevalence of respiratory symptoms, slows the rate of decline in pulmonary function, and may reduce functional impairments and improve tolerance for exercise. 5. Smoking cessation may help slow osteoporosis and reduce the risk of hip fractures, but effects on rates of bone loss or subsequent risk of fracture have not yet been studied adequately. 6. Continued smoking in late life is associated with the development and progression of several major chronic conditions, loss of mobility, and poorer physical function. Former smokers appear to have higher levels of physical function and better quality of life than continuing smokers. Physicians and others should encourage older adults to stop smoking. Of course, not every older adult who quits will benefit in all, or indeed any, of these ways. Nevertheless, at the population level, the prospects are excellent that smoking cessation after age 65 will extend both the number of years of life and the quality of life.

Age Factors↗
PubMed1991

Future research directions in cancer ecogenetics.

There are many productive directions for future research in cancer ecogenetics. Genetic variation in susceptibility to chemicals and other carcinogenic agents has been neglected in most epidemiologic and rodent investigations of cancer etiology. Genetic variation is important to characterization of risks for population subgroups. Genetic investigations also may enhance inquiries into the underlying mechanisms of carcinogenesis and of cancer prevention. Polymorphisms of cytochrome P450 mono-oxygenases, epoxide hydrolase, glutathione-S-transferases, and N-acetyltransferase offer important windows on biotransformation of pro-carcinogens. Assays in peripheral blood cells need to be related closely to variation in activity in target organs. Tumor suppressor genes, signal transduction pathways, and cell surface receptors are additional sites where genetic variation would be highly important to cancer risks.

Biotransformation↗
PubMed1991

Participation and adherence among older men and women recruited to the Beta-Carotene and Retinol Efficacy trial (CARET).

We evaluated as functions of age and gender participation and adherence rates in older adults recruited to pilot studies for CARET, a multicenter chemoprevention trial. Eligible were men and women aged 50-69 who were current or recent former smokers, and men aged 45-74 with occupational exposure to asbestos. We found negligible differences by age in response to recruitment mailings, drop out during the enrollment process and after randomization, and adherence to taking the study capsules. Men had numerically lower drop-out and higher adherence rates than women, but differences were not statistically significant. These results should encourage researchers to recruit older men and women (at least up to age 69) to clinical trials.

Age Factors↗
PubMed1991

CARET, the beta-carotene and retinol efficacy trial to prevent lung cancer in asbestos-exposed workers and in smokers.

CARET is a two-armed, double-blind, randomized chemo-prevention trial to test the hypothesis that oral administration of beta-carotene 30 mg/day plus retinyl palmitate 25,000 IU/day will decrease the incidence of lung cancer in high-risk populations: heavy smokers and asbestos-exposed workers who have smoked. The agents combine anti-oxidant and nuclear tumor suppressor mechanisms. Fastidious monitoring for possible side effects is facilitated by inclusion of a Vanguard population. As of 31 December 1990, 6,105 participants of the 18,000 needed have been randomized in the trial. Efficacy results are expected in 1999.

Aged↗
PubMed1990

Serum paraoxonase and its influence on paraoxon and chlorpyrifos-oxon toxicity in rats.

Paraoxon and chlorpyrifos-oxon, the active metabolites of the organophosphorus insecticides parathion and chlorpyrifos, respectively, are hydrolyzed by an "A"-esterase, paraoxonase, which is present in the sera of several mammalian species. In this study, we investigated whether levels of serum paraoxonase activity in laboratory animals can influence the in vivo toxicity of paraoxon and chlorpyrifos-oxon. Paraoxonase was found to be 7-fold higher in rabbit serum than in rat serum. The dose of paraoxon required to produce similar signs of toxicity and similar degrees of cholinesterase inhibition in rats and rabbits (0.5 and 2.0 mg/kg, respectively) differed by 4-fold. Paraoxonase was then purified from rabbit serum and 8.35 units was injected in the tail veins of rats, increasing the peak hydrolytic activity of rat serum by 9-fold toward paraoxon and by 50-fold toward chlorpyrifos-oxon. The increase in serum paraoxonase/chlorpyrifos-oxonase activity was long-lasting, with a 2- and 10-fold increase, respectively, still present after 24 hr. Thirty minutes following enzyme injection, rats were challenged with an acute dose of paraoxon or chlorpyrifos-oxon given by the intravenous, intraperitoneal, dermal, or oral route. Cholinesterase activities were measured in plasma, red blood cells, brain, and diaphragm after 4 hr. Rats pretreated with paraoxonase exhibited less inhibition of cholinesterase than vehicle-treated controls following identical doses of paraoxon, particularly when the organophosphate was given iv or dermally. A very high degree of protection, particularly toward brain and diaphragm cholinesterase, was provided by paraoxonase pretreatment in animals challenged with chlorpyrifos-oxon by all routes. These results indicate that levels of serum paraoxonase activity can affect the toxicity of paraoxon and chlorpyrifos-oxon.

Animals↗
PubMed1990

The degree of roentgenographic parenchymal opacities attributable to smoking among asbestos-exposed subjects.

Considerable controversy surrounds the question of whether cigarette smoking has the potential to increase the prevalence of small opacities on chest roentgenographs among asbestos-exposed workers. To compare the relative contribution of smoking with other predictors of the presence of roentgenographic small opacities, we examined 661 men enrolled in a double-blind, randomized trial designed to assess the efficacy of vitamin A and beta-carotene in the prevention of lung cancer among workers with heavy occupational asbestos exposure. Subjects in the study population had a mean latency of 35 yr from first asbestos exposure and a mean of 28 yr in their trade. The prevalence of roentgenographic abnormalities consistent with asbestos exposure was 26% for pleural abnormalities alone, 10% for parenchymal abnormalities alone, and 20% for pleural and parenchymal abnormalities together. We investigated occupation, age, latency from first asbestos exposure, and smoking status as predictors of roentgenographic small opacities. Smoking history, independent of latency, contributed to the prevalence and extent of small opacities, but its effect was less than that of latency. We conclude, that in the setting of heavy occupational exposure to asbestos, cigarette smoking confers added risk for the development of roentgenographic small opacities.

Aged↗
PubMed1990

Value-of-information analysis of testing strategies: estimating the effect of uncertainty about the proportion of chemicals that are true human carcinogens.

Choosing a cost-effective strategy for classifying chemicals as human carcinogens and non-carcinogens depends upon the costs of false positives (carcinogens erroneously treated as non-carcinogenic) and false negatives (non-carcinogens erroneously treated as carcinogenic); upon the accuracy (sensitivity and specificity) of the classification strategy; and upon the underlying proportion of carcinogens in the population of chemicals to be classified. If these values are known, value-of-information analyses can indicate the most cost-effective among three strategies: classify as carcinogenic without testing, classify as non-carcinogenic without testing, or choose the most cost-effective test and classify on the basis of the test result. When some or all of the values are uncertain, the analysis becomes more complex, but still helps to guide decisions among the three classification strategies.

Animals↗
PubMed1988

Beneficial six-year outcome of smoking cessation in older men and women with coronary artery disease. Results from the CASS registry.

We investigated the effects of cigarette smoking and cessation of smoking in a cohort of 1893 men and women from the Coronary Artery Surgery Study (CASS) registry who were 55 years of age or older and had angiographically documented coronary artery disease. The six-year mortality rate was greater among continuing smokers (n = 1086) than among those who quit smoking during the year before enrollment in the study and abstained throughout the study (n = 807) (relative risk, 1.7 [95 percent confidence limits, 1.4, 2.0]). Continuing smokers were also at higher risk of either myocardial infarction or death (1.5 [1.2, 1.7]). There was no diminution of the beneficial effect with increasing age. The relative risks of death were 1.7 (1.4, 2.1) and 1.6 (1.1, 2.3) for the groups 55 to 64 years old and 65 or older, respectively, and 1.6 (1.4, 1.9) for comparable subgroups among CASS subjects 35 to 54 years of age. When subjects were arrayed according to risk quartile, the benefits of smoking cessation were greatest in those at moderate risk. We conclude that smoking cessation lessens the risk of death or myocardial infarction in older as well as younger persons with coronary artery disease.

Adult↗
PubMed1988

Physical, morphological, and chemical studies of dusts derived from the machining of composite-epoxy materials.

This work (in three parts) inquires into whether respirable dusts derived from the machining of six composite-epoxy materials (e.g., aircraft industry) may pose a health risk to the operators. Dust samples representative of a variety of composites and structural components were aerodynamically sized and fractionated. Bulk and fractionated samples were examined by light and electron microscopy and analyzed chemically by thermogravimetry (TGA), gas chromatography (GC) and mass spectrometry (MS). Relative fractions of respirable to total mass of bulk samples were less than 3%; aerodynamic diameters of fractionated particles ranged from 0.8 to 2.0 microns. By microscopy, bulk particles ranged from 7 to 11 microns in diameter, with mean aspect ratios from 4 to 8:1. Mean diameter of fractionated particles was 2.7 microns. By TGA, weight losses were negligible below 250 degrees C and variable but elevated at temperatures up to 860 degrees C. In assays of vapors released at 250 degrees C, GC/MS indicated a variety of compounds in different amounts for each sample. We conclude that under the present machining protocols, dusts at the tool face contained few particles of respirable size with no evidence of splitting of fibers longitudinally and were of a low volatilizable chemical content. Overall, composites were judged to be well cured and thermally stable.

Chemical Phenomena↗
PubMed1988

Association of food frequency questionnaire estimates of vitamin A intake with serum vitamin A levels.

To assess the validity of nutrient intake estimates from a food frequency questionnaire, the authors compared estimates of intake of preformed retinol (dietary plus supplements), beta-carotene, other active carotenoids, and total vitamin A computed from questionnaire responses with serum retinoid and carotenoid concentrations. Data were obtained from 302 male and female current or former smokers, participants in a lung cancer chemoprevention trial at the Fred Hutchinson Cancer Research Center in Seattle, Washington, during 1985-1986. Both serum beta-carotene and serum alpha-carotene were associated, although weakly, with food frequency estimates of total vitamin A intake, dietary vitamin A, beta-carotene, other carotenoids, and total carotenoids (0.18 less than or equal to r less than or equal to 0.26). Serum retinol was associated with supplementary vitamin A intake (r = 0.16). Nondietary factors were also associated with serum nutrient concentrations--in particular, cigarette smoking, alcohol intake, and body mass index. Cigarette smoking emerged as an important modifying factor of the relation between serum beta-carotene and dietary beta-carotene (r = 0.14 for current smokers, r = 0.30 for former smokers).

Aged↗