Search

Human Bifidobacteriumsp strain bifidum(B. bifidum) was administered to BALB/c lactating mice (n= 58) and their litters (n= 327 pups) to evaluate the ingested strain's adherent properties and ability to inhibit murine rotavirus (MRV) infection. ELISA and anaerobic bacteriologic techniques were used to measure MRV shedding and colonization of Bifidobacteriumin the small intestine. At 13–16 d gestation, pregnant dams (and their expected litters) were randomly assigned to one of four experimental groups: 7) normal controls; 2) B. bifidum-treated only; 3) MRV-infected only; and 4) B. bifidum-treated + MRV-infected dams and litters. During the acute phase of diarrhea, 80 of small-intestine cultures in B. bifidum-treated litters were positive for the ingested B. bifidumstrain compared with 24 of fecal cultures. Examination of tissue cross sections under electron microscopy revealed the ingested B. bifidumstrain survived passage through the upper gastrointestinal tract and adhered to the small-intestine epithelium. After the administration of the high dose of virus, diarrhea developed in all pups, but onset was significantly delayed in B. bifidum-treated + MRV-infected litters compared with litters infected with MRV only (p< 0.02). B. bifidum-treated + MRV-infected pups demonstrated a significant reduction in MRV shedding compared with litters challenged with MRV only at d 2 to 10 after inoculation (p< 0.009). More direct studies are needed to assess mechanisms by which this anaerobe can alter the course of MRV infection at the level of gut epithelium.

To examine the belief that women with endometriosis have "voluntarily" delayed childbirth, the authors used a case-control approach to assess the relation between sexual, contraceptive, and reproductive factors and endometriosis. A total of 104 laparoscopically confirmed newly diagnosed cases of endometriosis were identified from a gynecologic specialty clinic in western New York state in 1987. Two control groups were used: 1) 100 friend controls, and 2) 98 medical controls. No differences were found between study groups on use of reliable birth control, use of birth control before a first pregnancy, age at first intercourse, frequency of intercourse, decisions to delay pregnancy, age at first pregnancy, or measures of body size. Cases were older than medical controls by about 1 year when they first began using birth control (19.8 vs. 18.6 years, p < 0.05). Cases were also 1 year older than friend controls when they began regular intercourse (20.9 vs. 19.5 years, p < 0.005) and at first marriage (22.8 vs. 21.7 years, p < 0.05). A larger percentage of cases than friend controls were never pregnant (p < 0.0001) and were more likely to have problems becoming pregnant (p < 0.0001). Results, overall, do not support simplistic assumptions that characterize endometriosis patients as career women who voluntarily delay pregnancy. Rather, the results point to a complex relation between endometriosis and reproductive, sexual activity, and fertility-related factors.

The authors studied 439 postmenopausal breast cancer cases, identified in hospitals throughout western New York, with an interview schedule that considered frequency and amount ingested of 172 foods and provided data for an estimate of total calories ingested. These were compared with age-matched controls comprising a random sample of the same communities as the cases. The extensive interviews, requiring 2.0 hours on average to administer, also covered alcohol ingestion, Quetelet index, and a wide variety of reproductive factors. The authors found, as have most investigators over the past 25 years, that risk increased with increases in age at first pregnancy, decreased with increases in numbers of children and pregnancies, and increased in those with history of benign breast disease and in those with female relatives previously affected with breast cancer. Risk adjusted for potential confounders was highest among women with the lowest ingestion of carotene or a substance correlated with its ingestion. Risk was not associated with retinol ingestion. It increased with increases in Quetelet index. Fat intake, whether studied in terms of quantity or the proportion of total calories derived from fat, was not associated with risk of breast cancer. Our analyses of these factors were adjusted for age, education, and the reproductive history traits described above.

The role of occupational exposure to heat and electromagnetic fields was investigated in a case-control study of male breast cancer. Seventy-one cases reported to the New York State Tumor Registry between 1979 and 1988 were compared with 256 healthy male controls. Controls were frequency matched to cases by race, year of diagnosis, and age in 5-year intervals. Unconditional logistic regression modeling indicated that males with occupations that involved heat exposure had an elevated risk for the disease. The age- and county-adjusted odds ratio was 2.3 (95% confidence interval (CI) 0.95-5.3). Exposure to heat on the job could influence testicular function. No increase in disease risk was observed for males believed to have occupational exposure to electromagnetic fields (odds ratio = 0.7, 95% CI 0.3-1.9).

The protective effect of a human strain ofBifidobacterium bifidum(B. bifidum) against murine group A rotavirus (MRV) was examined in the intestines of BALB/c infected mice. In experiments designed to determine whetherB. bifidummediated MRV shedding during diarrheal disease, pregnant dams (and their expected litters) were randomly assigned to the following groups: (1) mice infected with MRV alone; (2)B. bifidum-treated + MRV-infected mice; (3)B. bifidum-treated controls; and (4) saline control animals. An enzyme-linked immunosorbent assay (ELISA) for the detection of group A rotavirus was used to measure virus protein. The sensitivity of the MRV antigen detector ELISA was determined by serially diluting the rotavirus antigen in test samples. Antigen was detected in dilution ranges of 1:256–1:4096 during the acute phase and 1:16–1:512 in the recovery phase of MRV clinical disease, in the samples tested. Treatment withB. bifidumsignificantly reduced shedding of MRV antigen (P<0.009) on days 2–10 postinoculation. The reduction in shedding of virus protein corresponded well with delayed onset of acute diarrhea (P<0.02). Closer examination of tissue cross sections under electron microscopy revealed that theB. bifidum-ingested strain adhered to the epithelium of the small intestine. These results suggest that priming the intestine withB. bifidumis effective against experimental MRV challenge and confirmed the potential usefulness of this detector ELISA for studying the kinetics of group A rotavirus infection in animals and humans.

A number of authors have presented evidence that high dietary fat increases the risk of breast cancer, and a number have presented evidence to the contrary. In this study, dietary histories were obtained in 1980 from 18,586 postmenopausal women in New York State. These women were followed through 1987 to ascertain their incidence of breast cancer and other cancers and deaths from all causes, as registered in the New York State Tumor Registry and Office of Vital Statistics. Survival analysis revealed that the incidence of breast cancer increased with age, was higher among the nulliparous, was higher for those with a late (> 26 years) age at first pregnancy, and increased with increasing socioeconomic status--all risk factors discovered before for breast cancer. No increase in risk was related to the ingested amount of calories, vitamins A, C, or E, dietary fiber, or fat. Although dietary fat has been found to be associated with higher risk of cancer at a number of other sites, e.g., the lung, colon, and rectum, and although some previous writers have suggested an association with risk of breast cancer, the findings in three cohort studies as well as in eight substantial case-control studies are negative and suggest that a relation is far from established.

This study of 178 cases of cancer of the esophagus from three counties in western New York, as compared with sex- and age-matched neighborhood controls in 1975-1986, replicated some earlier findings, particularly with regard to the increased risks associated with use of cigarettes and alcohol. The concentration of alcohol in an alcoholic beverage apparently did not affect risk: Beer carried a substantial risk, whereas less-dilute forms of alcohol carried no risk. These findings also suggest that the risk of cancer of the esophagus increases with ingestion of foods containing retinol but not carotene. Although increased risks were found to be associated with increases in total calories and fat ingested, as well as calcium, they appeared to be confounded with the risk associated with retinol, as distinct from carotene. Inasmuch as a difference in risk associated with retinol and carotene has been shown in a few previous inquiries dealing with esophageal cancer and cancer at other sites, a need for further investigations distinguishing risks associated with the two compounds is apparent.

In a study of 250 cases of cancer of the testis and of neighborhood- and age-matched controls in upstate New York in 1977-1980, the authors found that risk was enhanced by possession of a number of traits associated with exposure of the testis to heat; occupational exposures to fertilizers, phenols, and fumes or smoke; and trauma to the testis. Risk was also increased for characteristics related to congenital and developmental aberrancies and testis-related abnormalities, e.g., low sperm count, fertility problems, atrophic testis, and cryptorchidism. Several of these risk factors were statistically significant in a multiple regression model that adjusted for all other significant traits, age, and education.

The authors interviewed 428 pathologically confirmed cases of colon cancer and controls matched on age, sex, race, and neighborhood in the New York counties containing the cities of Buffalo, Niagara Falls, and Rochester. Risk of colon cancer in both males and females, studied separately, appeared to increase with the amount of total fats and total calories ingested. In addition, we found the risk to increase with increases in the Quetelet index of relative weight (weight (kg)/height (m)2). Dietary fiber was only equivocally associated with risk. Fats and Quetelet index were associated with increased risk in a regression analysis adjusting each factor for the other, as well as for fiber, age, and socioeconomic status. The same was true for calories and Quetelet index. Future efforts to clarify a possible protective role for fiber and to disentangle the effects of fats and calories need to be undertaken. The fact that calories ingested and obesity are each associated with increased risk suggests the importance of studying calorie expenditure.

The authors used data on patients aged 30-79 years admitted to the Roswell Park Memorial Institute in Buffalo, New York, 1957-1965, to compare the amount of lifetime occupational physical activity for 210 white male patients with cancer of the colon and 276 white male patients with cancer of the rectum to the lifetime occupational physical exercise of 1,431 patients with nonneoplastic nondigestive diseases. The authors found that risk of cancer of the colon increased with increasing amount and proportion of time in jobs involving only sedentary or light work. This relationship was not found for rectal cancer. These findings corroborate those of Garabrant et al. (Am J Epidemiol 1984; 119:1005-14). The strength of the associations presented here and the dose-response relationship indicate that limited physical activity could be an important etiologic factor. More inquiries need to be undertaken to study exercise in relation to other factors, such as diet, in colon cancer risk.

The authors conducted a study of 404 melanoma patients and 521 control patients of both sexes at Roswell Park Memorial Institute. As have previous investigators, they found that higher risk attaches to upper socioeconomic status, as measured by occupation and education, lightness of complexion and hair, and amount of blue in the admixture of eye color. The authors also found a higher risk among individuals who reacted to sun exposure by burning, blistering, or freckling rather than by tanning. A particular concern was to measure risk associated with exposure to the sun. As have two other investigators, they found that risk decreased with increasing exposure, suggesting either that individuals continually exposed to the sun have less risk because of tanning, or that susceptibles purposely avoid sun exposure, or both. The fact that melanoma occurs with greater frequency on sites exposed to the sun suggests that sun exposure plays a part. These studies showed a dose-response increase in risk (odds ratios of up to 4 for males and over 6 for females) with increases in number of traits possessed, such as light complexion, and burning or freckling in response to sun exposure. This is consistent with the authors' earlier finding of a strong familial aggregation of melanoma.

A major barrier to the conduct and interpretation of retrospective studies of diet and cancer has been uncertainty about the reliability of retrospective measures of diet from the distant past. The authors therefore conducted a study to assess the reliability of retrospective dietary reports and to determine whether the retrospective report or the report of current diet is the better indicator of past diet. Persons (n = 323) originally interviewed regarding their diets in 1975-1979 were retrospectively reinterviewed in 1984-1985. There was little difference between the retrospective reports and the reports of current diet when group means were examined as indicators of past diet. The retrospective reports tended to overestimate the past frequency of consumption for most foods, whereas the reports of current diet tended to yield underestimates. Because food frequency-based dietary history data are more useful for ranking study subjects than for generating estimates of group means, correlation analysis was used as the principal assessment of the reliability of the two indicators of past diet. The retrospective reports more closely correlated with the diet reported at the original interview than did the report of current diet (for 37 of 47 foods). Nutrient indices based on the retrospective history were also more highly correlated with those of the original diet than were indices based on the current diet. No differences were noted in the reliability of retrospective reports according to age or sex. Subjects accurately reported perceptions of changes in their consumption of most foods, yet an estimate of past diet created by adjusting current diet for perceived change did not correlate more highly with the original diet than did the retrospective report. The authors conclude that assessing current diet to make inference about diet from the distant past does not yield more reliable estimates of past diet than does the retrospective dietary history. The best estimate of diet from several years in the past may be derived directly from a retrospective dietary history which focuses on that past period of time.

There is considerable interest in developing a means of assessing dietary intake of specific nutrients with minimal time and expense in epidemiologic studies. Using data from 1,682 individuals who were interviewed using an extensive food frequency dietary history, the authors examined the question of how many foods might be minimally required in order to estimate specific nutrient intakes for epidemiologic purposes. Nutrient indices were constructed for vitamins A and C, dietary fiber, fat, protein, and total calories based on 128 foods included in the interview. They found that a large fraction of the variability of nutrient intake in this population could be explained by a small number of foods. An abbreviated dietary history ascertaining the intake of as few as 15-20 food items may be all that is required in order to test the association between disease outcome and the intake of a single nutrient.

If small effects of exposure on disease outcome are to be appropriately assessed, it is necessary to consider all potential sources of the fluctuation of relative odds. The authors consider the impact of differential variance in case and control exposure reports on the magnitude of the observed relative odds. With equal dispersion of case and control exposure, a difference in mean exposure generally produces a dose-response increase in relative odds. The combination of equal mean and unequal dispersion of case and control exposure produces a curvilinear pattern of relative odds. Greater mean exposure and dispersion of exposure among cases produce odds ratios lower than those that would be observed if dispersion among cases and controls were equal. Conversely, less dispersion among cases than among controls produces higher relative odds estimates. Differential error as a source of differential dispersion constitutes a potentially important source of bias.