Synergistic effect between alcohol and estrogen replacement therapy on risk of breast cancer differs by estrogen/progesterone receptor status in the Iowa Women's Health Study

Two cohort studies have reported that alcohol and estrogen replacement therapy (ERT) act synergistically to increase the incidence of breast cancer. Possible interactions between alcohol consumption and family history of breast cancer or body mass index were also reported in the Iowa Women's Health Study data. In the Iowa Women's Health Study cohort, alcohol appears to be associated only with estrogen receptor-negative (ER-)/progesterone receptor-negative (PR-) breast cancers. Therefore, we investigated whether the interactions between alcohol and other risk factors differ according to ER/PR status. In January 1986, participants completed a questionnaire that included alcohol intake and other information. Through 1992, 939 breast cancer cases occurred among 37,105 postmenopausal women at risk. Cox proportional hazards regression was used to compute adjusted relative risks and to test for multiplicative interactions. Relative risks of ER+/PR+, ER+/PR-, and ER-/PR- breast cancer for women who consumed > or = 4.0 g of ethanol/day and reported ever using ERT compared to abstainers who never used ERT were 1.8, 1.3, and 2.6, respectively. Relative risks of ER+/PR+, ER+/PR-, and ER-/PR- breast cancer associated with any alcohol intake and a positive family history of breast cancer compared to abstainers with no family history of breast cancer were 1.7, 0.8, and 3.1, respectively. Relative risks of ER+/PR+, ER+/PR-, and ER-/PR- breast cancer associated with the highest quintile of body mass index and drinking > or = 4.0 g of ethanol/day compared to abstainers in the lower four-fifths of body mass index were 0.9, 1.8, and 2.0, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac troponin I phosphorylation increases the rate of cardiac muscle relaxation

Cardiac troponin (Tn) I (CTnI), compared with skeletal TnI, contains extra amino acids (32 to 33) at its amino terminus, including two adjacent serine residues. These two serine residues are believed to be phosphorylated by protein kinase A (PKA) upon stimulation of the heart by beta-agonists. In this study, we found that phosphorylation of a cardiac skinned muscle preparation by PKA, mainly at CTnI, results in a decrease in the Ca2+ sensitivity of muscle contraction. The pCa50 decreased by approximately 0.27 +/- 0.06 pCa units upon phosphorylation. To study cardiac muscle relaxation, we used diazo-2, a photolabile Ca2+ chelator with a low Ca2+ affinity in its intact form that is converted to a high-affinity form after photolysis. We found that the rate of cardiac muscle relaxation increased from a time of half-relaxation (t1/2) = 110 +/- 10 milliseconds to t1/2 = 70 +/- 8 milliseconds after CTnI phosphorylation. This result demonstrates that CTnI phosphorylation can be linked with the increased rate of muscle relaxation in a relatively intact muscle preparation. Since CTnI phosphorylation has been shown previously to affect the Ca2+ affinity and Ca2+ off-rate of CTnC in vitro, it is likely that the faster relaxation seen here reflects faster dissociation of Ca2+ from cardiac TnC (CTnC). Model calculations show that increased dissociation of Ca2+ from CTnC, coupled with the faster uptake of Ca2+ by the sarcoplasmic reticulum stimulated by PKA phosphorylation of phospholamban, can account for the faster relaxation seen in the inotropic response of the heart to catecholamines.

Progesterone and estrogen receptors and mammary neoplasia in the Iowa Women's Health Study: how many kinds of breast cancer are there?

Characterization of breast tumors on both estrogen receptor (ER) and progesterone receptor (PR) status suggests distinct biological and clinical profiles. We hypothesized that these tumor subtypes might also show specific differences in their relations with epidemiologic risk factors. Risk factors were assessed via a questionnaire mailed in January 1986 to 37,105 cancer-free women, ages 55-69 years: the Iowa Women's Health Study. To the end of 1992 (241,627 person-years of follow-up), 939 incident breast cancers were ascertained by the Iowa population-based Surveillance, Epidemiology, and End Results Cancer Registry. Joint ER and PR status was determined on a total of 610 (65%) tumors. Three patterns of association were seen in relation to epidemiologic risk factors. Endogenous hormone exposure variables--parity, age at first birth, age at menarche, body mass index, and body fat distribution as defined by waist-to-hip ratio--showed their expected pattern of associations only with PR+ breast cancers. In age- adjusted and polychotomous logistic regression analyses, both ER-PR- and ER+PR- breast cancers showed evidence of an inverted pattern of associations with several risk factors compared with that seen for ER+PR+ cancers [including parity (ER-PR-), waist-to-hip ratio (ER-PR-), body mass index (both), body mass index at age 18 years (ER-PR-), history of bilateral oophorectomy (ER+PR-), and oral contraceptive use (ER+PR-)]. Family history was not associated with ER+PR- cancers; only 8 (8%) of 99 patients with this subtype had a family history of breast cancer compared with 16% of all other types combined.(ABSTRACT TRUNCATED AT 250 WORDS)

Response rates among control subjects in case-control studies

Response rates are an important component of epidemiologic research. The purposes of this study are (a) to evaluate how response rates are defined and calculated for control subjects in epidemiologic case-control studies, and (b) to explore factors that may impact response in epidemiologic studies. Our results show that the method of control subject selection has an impact on study response. Gender of respondent does not appear to impact response rates. However, response rates are generally worse for individuals less than 45 years old. Methods used to calculate response have a great impact on "response rate"; therefore, it is important for researchers to define exactly what the reported response rates represent and how they are derived so that data can be interpreted appropriately.

Early body size and subsequent weight gain as predictors of breast cancer incidence (Iowa, United States)

We examined whether associations of adult weight gain with the risk of postmenopausal breast cancer vary by stature, waist-hip ratio (WHR), and early adult size in a cohort of 37,105 Iowa (United States) women. Both low body mass index (kg/m2) (BMI) at age 18 and high subsequent weight-gain were associated independently with increased risk of incident postmenopausal breast cancer. After stratifying on BMI at age 18, high weight gain was associated with increased risk irrespective of whether early BMI was low (relative risk [RR] = 1.92, 95 percent confidence interval [CI] = 1.45-2.53) or high (RR = 1.59, Ci = 1.19-2.12). Women with lower BMI at 18 were at a higher risk at all levels of weight change, but having low BMI at age 18 and low subsequent weight gain conferred no significantly excess risk over those with high BMI at 18 and low gain. An inconsistent increase in risk was associated with taller stature; there was no additional risk associated with high WHR. Part of the observed risk from lower early size may reflect greater weight gain by lighter women. Limiting adult weight gain thus may be a feasible method to avoid increasing an individual's risk of breast cancer. Reasons for different effects of early cf late weight gain are not established, but benefits of a greater size at age 18 are likely to be offset by increased risks of other weight-related diseases at older ages.

A direct regulatory role for troponin T and a dual role for troponin C in the Ca2+ regulation of muscle contraction

Troponin (Tn), containing three subunits: Ca2+ binding (TnC), inhibitory (TnI), and tropomyosin binding (TnT), plays a crucial role in the Ca2+ regulation of vertebrate striated muscle contraction. These three subunits function by interacting with each other and with the other thin filament proteins. Previous studies suggested that the primary role of TnT is to anchor the TnI.TnC complex to the thin filament, primarily through its interactions with TnI and tropomyosin. We propose here a new role for TnT. Our results indicate that, when TnT is combined with the TnI.TnC complex, there is an activation of actomyosin ATPase that is Ca(2+)-dependent. To determine whether the latter results from a direct effect of TnC on TnT or indirectly from an effect of TnC on TnI which is transmitted to TnT, we prepared a deletion mutant (deletion of residues 1-57) of TnI, TnId57 (Sheng et al. (1992) J. Biol. Chem. 267, 25407-25413), which interacts with TnC but not TnT. Both wild type (TnI.TnC.TnT) and mutant (TnId57.TnC.TnT) Tn complexes demonstrated equivalent activity in the Ca2+ regulation of actomyosin-S1 ATPase activity. Similarly, both TnI and TnId57 could equally reconstitute TnI-depleted skinned muscle fibers. Therefore, since TnId57 does not interact with TnT, these results suggest that TnT reconstitutes native Ca2+ sensitivity via direct interaction with TnC. Thus Ca2+ binding to TnC would have a dual role: 1) release of the ATPase inhibition by TnI and 2) activation of the ATPase through interaction with TnT.

Epidemiologic and genetic follow-up study of 544 Minnesota breast cancer families: design and methods

In 1944, a case-control family study was initiated at the Dight Institute for Human Genetics at the University of Minnesota to study the influences of childbearing breastfeeding, and hereditary susceptibility on the occurrence and age-of-onset of breast cancer. Index cases (probands) were women ascertained at the Tumor Clinic of the University of Minnesota Hospital. Medical history and life style information were obtained on probands and relatives, and all cancers were histologically verified. A total of 544 families were studied, with probands diagnosed between 1931 and 1952. All of the records and pathology slides have been maintained from the original study; for most probands this includes the original tissue blocks. We are conducting a historical cohort study of selected of selected first- and second-degree female relatives (sisters, daughters, nieces, granddaughters) of the probands and a group of control women identified as the spouses of all male first- and second-degree relatives (brothers, sons, grandsons, and nephews). The subsequent development of breast cancer is being determined to quantify the absolute risk associated with a positive family history. Current disease status is ascertained with mammography, and stromal density is measured using digital imaging. Segregation analysis will be applied to examine how non-genetic factors such as diet, exogenous hormone use, and body fat distribution influence risk in women at high risk because of family history. A subset of families are being selected for molecular analysis of the BRCA1 gene or for linkage analyses to identify putative susceptibility loci other than BRCA1. Documented cancer histories were known for at least three generations, and the current study extends the pedigrees up to four or five generations for every family, allowing a detailed description of familial risk. This cohort study of breast cancer families is likely to be important in both quantity and quality of data and will serve as a major genetic epidemiologic resource, being free of selection bias and having relevant non-genetic exposure determined in at least four generations.

Segregation analysis of breast cancer in a population-based sample of postmenopausal probands: The Iowa Women's Health Study

Inheritance of a major susceptibility gene for breast cancer has been primarily investigated in families with early-onset disease. However, familial clustering of late-onset breast cancer is well documented, and genetic factors may also be relevant. In the Iowa Women's Health Study, we evaluated evidence for a major gene after allowing for measured environmental risk factors. Two hundred sixty-five incident breast cancer probands were identified from a prospective cohort study of 41,837 women aged 55 to 69 years at baseline in 1986. A pedigree development form was mailed to the probands to ascertain all first-degree female relatives. A questionnaire and body measurement protocol were mailed to identified living relatives or surrogates. Segregation analyses were conducted on a total of 1,145 women in 251 families using regressive models as implemented in S.A.G.E. Mendelian codominant inheritance of an allele that produced an earlier-age-at-onset provided the best fit to the data. Incorporation of measured environmental risk factors as covariates yielded no significant improvements in the likelihoods. Approximately 50% of this population could be expected to carry a late-onset breast cancer susceptibility gene, and 23% of the population is susceptible because of the environment in which they live. Homozygous gene carriers are predicted to have a mean age-at-onset of 48 years, over 20 years earlier than heterozygotes; few cases would be expected among non-gene carriers. In conclusion, the transmission pattern of late-onset breast cancer may be determined by a common susceptibility gene.

Dietary fat and risk of breast cancer according to hormone receptor status

The association of dietary fat with breast cancer in prospective cohort studies has generally been weak and not statistically significant. However, these studies have not considered whether the risk related to fat intake may differ according to estrogen or progesterone receptor status. Dietary habits and other breast cancer risk factors were assessed by mailed questionnaire in January 1986 in 34,388 postmenopausal Iowa women. Through 1991, 724 incident breast cancer cases were ascertained in this cohort using the Iowa cancer registry. Joint estrogen and progesterone receptor status was determined for 479 (66%) breast cancers. For tumors that were positive for both estrogen and progesterone receptors (ER+/PR+) (n = 329), age- and energy-adjusted relative risks for breast cancer adjusted from lowest to highest third of fat intake were 1.0, 1.05, and 1.22 (P trend = 0.14). Corresponding risks for ER+/PR- tumors (n = 75) were 1.0, 0.85, and 1.05 (P trend = 0.86) and for ER-/PR- tumors (n = 61) were 1.0, 1.06, and 0.73 (P trend = 0.68). Only 14 cases were classified as having ER-/PR+ tumors. Adjustment for other breast cancer risk factors did not appreciably alter these findings. There was a suggestion that dietary fat may be associated with ER+/PR+ breast cancers and not other breast cancers. These results are also consistent with an interpretation of no association between dietary fat with breast cancer, regardless of hormone receptor status. It has been suggested that etiological studies of breast cancer should investigate associations according to receptor status. This study provides evidence of a subset of breast cancers that may be related to dietary factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Familial clustering of breast and prostate cancers and risk of postmenopausal breast cancer

BACKGROUND

Previous studies have suggested that cancers of the breast and prostate cluster in families and that the presence of both diseases in a family may be associated with increased risk of breast cancer.

PURPOSE

Our purpose was to evaluate whether 1) prostate cancer aggregates in families with postmenopausal breast cancer, 2) families with cancers of the breast and prostate are the same ones as families with cancers of the breast and ovary, and 3) a family history of prostate cancer is associated with increased risk of postmenopausal breast cancer.

METHODS

We analyzed data from a large prospective cohort study of Iowa women that were (at baseline) aged 55-69 years in 1986. At the third follow-up survey in 1992, self-reported data on family history of breast, ovarian, and prostate cancers in parents and siblings were provided by 30,883 women. Additional information was collected to ascertain whether the age-of-onset of breast cancer in mothers or sisters was before or after the age of 45 years. Cancer occurrence was documented using the State Health Registry of Iowa.

RESULTS

History of prostate cancer in their father or a brother was reported by 3384 (11.0%) of the women, and a total of 4090 women (13.2%) reported breast cancer in their mother or a sister. A positive family history of both cancers was reported by 556 women, significantly (two-sided P < .001) greater than the 457 women expected if the family histories were independent. The aggregation of breast, prostate, and ovarian cancers was reported by 22 participants, greater than the 2.7 expected (two-sided P < .0001). During 6 years of follow-up, 578 breast cancers were identified in the cohort at risk. Compared with women without a family history of either cancer, women with a family history of breast cancer had a relative risk (RR) of 1.37 (95% confidence interval [CI] = 1.06-1.79) if the affected relative had onset after the age of 45 years, and an RR of 1.71 (95% CI = 1.13-2.61) if the affected relative had onset at or before the age of 45. A family history of prostate cancer in the absence of a family history of breast cancer was associated with an RR of 1.19 (95% CI = .90-1.56). However, a family history of both breast and prostate cancers was associated with RRs of 2.06 (95% CI = 1.23-3.45) and 2.35 (95% CI = .97-5.67) for breast cancer onset in relatives of greater than 45 and less than or equal to 45 years, respectively.

CONCLUSIONS

These observations are concordant with recent reports that suggest a shared familial risk (inherited or environmental) for these hormone-dependent malignancies.

Objective system for interviewer performance evaluation for use in epidemiologic studies

In this paper, the authors present an objective system to evaluate interviewer performance for use in epidemiologic studies. With this quality control system, all study interviews are audio-taped, and a random sample of interviews are coded according to interviewer behaviors, such as whether the interviewer asked the questions exactly as written and used the probes appropriately. With the use of data obtained from a large case-control study of colon cancer, the authors observed that 94.2% of all questions were asked in the same manner by all interviewers and that 89.5% of all probing behaviors were appropriate. They show that questions that required additional interviewer behaviors were more likely to result in variation in response that can be attributed to the interviewer. These findings have implications for study design and interpretation of study results. From simulations, the authors have estimated the impact of uncorrected interviewer variability on study power and ability to detect disease associations. Uncorrected interviewer variability could decrease study power from 84% to 56%. From simulations, the authors observed that odds ratios could be biased downward from 1.8 to 1.3. These findings illustrate the importance of using a continuous quality control program in epidemiologic research.

Age and risk factors for colon cancer (United States and Australia): are there implications for understanding differences in case-control and cohort studies?

Data from two population-based case-control studies were used to investigate the effect of age on colon cancer risk. Dietary intake data were assessed from a study conducted in Utah (United States) between 1979 and 1983; reproductive data were assessed from a study conducted in Adelaide (Australia) between 1979 and 1980. Data from both studies were assessed for their impact on those less than 65 years of age and those 65 or more years of age. Intake of energy, fat, and protein had a greater impact on risk among older men than among younger men. Risk estimates for the upper quartile of intake relative to the lowest quartile of intake were 8.5 (95 percent confidence interval [CI] = 1.7-43.0) for energy, 8.2 (CI = 1.6-41.3) for protein, and 7.2 (CI = 1.6-31.4) for total fat for older men, while comparable risk estimates were 2.4 (CI = 0.6-9.1) for energy, 3.0 (CI = 0.7-13.6) for protein, and 1.9 (CI = 0.5-7.1) for total fat among younger men. Similar trends were seen for older women for energy and protein. beta-carotene decreased colon cancer risk among younger men (odds ratio [OR] = 0.4, CI = 0.1-1.2) and women (OR = 0.1, CI = 0.1-0.5), although not among older men (OR = 1.2, CI = 0.3-4.9) and women (OR = 1.9, CI = 0.6-64). Calcium decreased risk of colon cancer among older men (OR = 0.1, CI = < 0.1-0.8) and younger women (OR = 0.2, CI = < 0.1-0.7).(ABSTRACT TRUNCATED AT 250 WORDS)

Predictors of cancer prevention attitudes and participation in cancer screening examinations

BACKGROUND

Few current data are available regarding factors associated with participation in cancer screening examinations in the general population.

METHODS

To identify factors associated with participation in cancer screening examinations, random population samples of 25- to 74-year-old men and women in six various-sized communities in three upper-Midwestern states (n = 4,915) were surveyed in 1987-1989. Multivariate-adjusted means were calculated and compared using analysis of covariance.

RESULTS

Statistically significant (P < 0.05) strong predictors (other than age and sex) of ever having had a specific cancer screening test were as follows (the numbers in parentheses following each listed association are the absolute maximum differences in mean proportions among the levels of the predictors): (1) rectal examination: higher education (14%); (2) fecal occult blood testing: higher education (6%) and never smoker (5%); (3) sigmoidoscopy: higher income (7%) and higher education (6%); and (5) mammography: higher income (25%), higher education (8%), and a positive family history of breast cancer (7%). There were no strong predictors (out of nine) of ever having had a Papanicolaou smear or a breast self-examination.

CONCLUSIONS

The largest differences among the population for participation in cancer screening examinations involves income and the two most expensive cancer screening tests: higher income is a strong predictor of having a mammogram and, to a lesser extent, of having a sigmoidoscopy. The most consistent predictor of participation in cancer screening examinations across all cancer screening tests is education: higher education is a predictor of having each kind of cancer screening test.

Examination of the effect of nongenetic risk factors on the familial risk of breast cancer among relatives of postmenopausal breast cancer patients

Relatives of postmenopausal breast cancer patients have a greater risk of breast cancer than do women with no family history of the disease. However, no study has previously examined the contribution of other breast cancer risk factors to risk in these relatives, thus precluding the ability to discern between shared environment or genes as the cause of familial aggregation. We conducted a nested case-control study of 251 index case families and 234 index control families. Incident breast cancer cases occurring in 1988-1989 and cancer-free controls were selected from a prospective cohort study. A pedigree development form was mailed to identify female relatives, who were then mailed a health history questionnaire. Index cases were significantly more likely than index controls to have at least one first-degree female relative with breast cancer [odds ratio = 1.62; 95% confidence interval = 1.03-2.54] after controlling for the total number of first-degree female relatives. After excluding the index cases and controls, logistic regression models were used to predict the odds of breast cancer in sisters (n = 72 cases). Sisters of index cases had slightly, although not statistically significant, elevated risk of both early-onset (age < 50 years; odds ratio = 1.34; 95% confidence interval = 0.54-3.30) and late-onset (age > or = 50 years; odds ratio = 1.56; 95% confidence interval = 0.87-2.79) breast cancer. Adjustment for nongenetic risk factors increased the odds ratio to 1.41 and 1.81, respectively. These data suggest that risk to sisters of postmenopausal breast cancer cases may be increased for both early- and late-onset breast cancer and this risk is apparently independent of measured risk factors.

Dietary cholesterol, fat, and lung cancer incidence among older women: the Iowa Women's Health Study (United States)

To test the hypothesis that a high intake of dietary cholesterol and fat is associated with elevated risks of lung cancer, we analyzed data from a population-based, prospective, cohort study conducted among 41,837 postmenopausal Iowa (United States) women who completed, in 1986, a comprehensive mailed questionnaire including information on usual intake of 127 food items. All cohort members were followed for cancer incidence through the statewide cancer registry. By 1991, after six years of follow-up, 272 incident lung-cancer cases were identified. After controlling for total energy intake and other confounding factors, dietary cholesterol, total fat, and animal fat were unrelated to lung cancer risk. Intake in the upper three quartiles of plant-derived fat, however, was related to a 30 to 40 percent lower incidence of lung cancer, comparative with those in the lowest quartile, with more pronounced reduction in risk observed among smokers (relative risk = 0.6, 95 percent confidence interval = 0.4-0.9). This prospective cohort study suggests that high intake of fat of plant origin may be associated with reduced risk of lung cancer, while dietary cholesterol and animal fat intake is unrelated to the etiology of this malignancy in postmenopausal women.

Familial aggregation and heritability of waist-to-hip ratio in adult women: the Iowa Women's Health Study

The aim of this study was to assess evidence that genetic factors influence body fat distribution. First-degree relatives of 324 cancer-free females in a population-based prospective study of 41,837 women (99% white) between the ages of 55 and 69 at baseline in 1986 were studied. A total of 396 living sisters (mean age 65.7 years) and 446 living daughters (mean age 41.2 years) were identified through a mailed 'family tree' questionnaire sent to each participant. Family members were mailed a questionnaire to obtain self-reported measures of current height and weight. A paper tape measure and written instructions were enclosed to obtain waist and hip circumferences. The age-adjusted mother-daughters correlations for waist-to-hip ratio and body mass index (kg/m2) were 0.19 and 0.23, respectively (P < 0.05 using Fisher's z-transformation). The corresponding sister-sister correlations were 0.23 and 0.19, respectively (P < 0.05). The sister-sister correlations were not significantly different from the mother-daughter correlations. After adjustment for body mass index the mother-daughter correlation for waist-to-hip ratio increased to 0.20 and the sister-sister correlation increased to 0.26. These familial correlations suggest that genes and common environment may contribute 40 to 50% of the total variance of waist-to-hip ratio in white women in the Midwest.

Segregation analysis of smoking-associated malignancies: evidence for Mendelian inheritance

Tobacco consumption is an established risk factor for cancer at a number of sites: oral cavity, esophagus, nasopharynx, lung, larynx, pancreas, bladder, kidney, and uterine cervix. These sites also demonstrate familial aggregation. To determine if evidence exists for a major gene controlling susceptibility to smoking-associated cancers, maximum likelihood segregation analyses were performed on 337 families (3,276 individuals) ascertained through a deceased lung cancer proband. Models were fitted that allowed for personal tobacco use and variable age of onset. The hypotheses of environmental transmission and no major gene were rejected (P < 0.005), but none of the Mendelian models could be distinguished. According to Akaike's Information Criterion, Mendelian dominant inheritance of an allele that produces cancer at an earlier age of onset provided the best fit to the data. The model suggests that 62% of the population are susceptible, and that the mean age-of-onset differs for men and women: at the mean level of tobacco exposure, female gene carriers are affected, on average, 24 years earlier than non-carriers (77 vs. 101), while in males the difference was 20 years (71 vs. 91). These findings extend our earlier observations on the genetic epidemiology of lung cancer and suggest that Mendelian factors may influence the risk of cancers that are known to be smoking associated.

Plasma carotenoids as biomarkers of vegetable and fruit intake

Higher intakes of vegetables and fruits are associated with a lower risk of certain human cancers. A biomarker of vegetable and fruit intake would be a valuable research tool. A cross-sectional study assessed the association between plasma carotenoid concentrations and intakes of vegetables and fruits. Plasma carotenoids (alpha-carotene, beta-carotene, lutein, beta-cryptoxanthin, and lycopene) were measured in 50 male and 49 female participants, aged 18-37 years, with a wide range of habitual vegetable and fruit intakes. Dietary intakes were assessed via a food frequency questionnaire. Intake of vegetables and fruits and high carotenoid foods were measured. The sum of the plasma carotenoids (excluding lycopene) was highly correlated with intake of total vegetables and fruits (r = 0.59). Of the individual plasma carotenoids, plasma alpha-carotene had the highest correlation with intakes of both total vegetables (r = 0.50) and total fruits (r = 0.58). Intakes of foods with high carotenoid contents were correlated with their corresponding plasma concentrations as follows: high beta-carotene foods (r = 0.41); high lutein foods (r = 0.46); and high lycopene foods (r = 0.11). Multiple regression analyses showed that intake of total vegetables and fruits was the most significant determinant of each plasma carotenoid except lycopene. The utility of combining the plasma carotenoids as biomarkers of vegetable and fruit intake was assessed by a stepwise regression of total vegetable and fruit intake on plasma carotenoids. Significant determinants of intake of total vegetables and fruits were alpha-carotene, beta-cryptoxanthin, lutein, and energy intake (R2 = 0.53).(ABSTRACT TRUNCATED AT 250 WORDS)

Statistical analysis of proliferative index data in clinical trials

Measurements of proliferative activity in colonic epithelial cells are being used as surrogate endpoints in clinical trials for colon cancer prevention. Proliferative index data exemplify an important type of clinical trial endpoint. The outcome variable is a proportion in which the denominator is an ancillary statistic and in which measurement error and technician judgement are important sources of variability. The paper proposes a statistical model for a repeated measures clinical trial with this type of endpoint, in the context of proliferative activity data. The model is a two-stage random effects linear model in the log scale. In addition to fixed effects covariates, it explicitly incorporates two major sources of variability: the number of epithelial cells counted and the reader effect. Although the resulting likelihood is complicated, one can fit an approximate likelihood with minimal loss of efficiency using standard packages. We apply the model to a pilot randomized clinical trial.

Handedness and mortality risk in older women

Left-handedness has been associated with decreased longevity, although this finding is controversial and not universal. The authors prospectively studied 39,691 women aged 55-69 years from the Iowa Women's Health Study through 5 years of mortality follow-up. No increase in mortality risk was found for left-handed women as compared with right-handed women (age-adjusted hazard ratio 1.10, 95% confidence interval (CI) 0.86-1.39) or for ambidextrous women (age-adjusted hazard ratio 1.05, 95% CI 0.73-1.49). Adjustment for body mass index, body fat distribution, smoking, and education did not alter these findings. Further analysis by cause-specific mortality (breast cancer, all other cancer, and circulatory disease) showed no relation to handedness. There was no difference in the mean age at death of left-handed, right-handed, and ambidextrous women. These findings do not support an association between left-handedness and increased mortality risk.

The thiadiazinone EMD 57033 speeds the activation of skinned cardiac muscle produced by the photolysis of nitr-5

EMD 57033 is thought to produce its potentiating effect by increasing the apparent Ca2+ sensitivity of the myofilaments, possibly by altering the kinetics of actomyosin interaction. We have investigated the effect of 10 microM EMD 57033 upon activation speed, induced by flash photolysis of 2mM nitr-5 (caged Ca2+), in chemically skinned trabeculae from the guinea-pig at 12 degrees C. EMD 57033 increases the half time of activation from 238 +/- 18.5 msec (n = 6) to 132.1 +/- 34.0 msec (n = 8) (mean +/- s.e.m.) and suggests that this Ca2+ sensitiser has an important effect upon fapp, that is the transition from the non-force to force generating cross-bridge states.

Egg consumption and cancer of the colon and rectum

We systematically reviewed 15 previous case-control and cohort studies that examined egg consumption as a risk factor for cancers of the colon and rectum. Nine of the 11 studies of colon cancer reported risk estimates consistent with a positive association; in three of these studies the association was statistically significant. The positive association for egg consumption was generally stronger for females than for males, and for cancer of the proximal, rather than distal colon. Six of eight studies of cancer of the rectum reported risk estimates consistent with a positive association; in two of these studies the association was statistically significant. Notably, in every study that met specific design criteria (defined a priori), risk estimates were consistent with a positive association. Two studies reported seven- to eight-fold increases in risk with high egg consumption. In some studies, positive associations remained after adjustment for intakes of macronutrients or for other food groups. The presence of a variety of bioactive compounds, including cholesterol, lends biological plausibility to a role of egg consumption in the aetiology of colorectal cancer.

Effect of consumption of whole milk and skim milk on blood lipid profiles in healthy men

A controlled crossover feeding study was conducted in eight males aged 20-36 y to compare the effects of skim milk and whole milk on blood lipids. For 6-wk diet periods, 236 mL/4191 kJ of skim or whole milk was consumed with a background diet designed according to the American Heart Association recommendations. Plasma lipids were analyzed at baseline and at 3 and 6 wk. After 6 wk, the mean total cholesterol concentration was 4.47 mmol/L with skim milk and 4.80 mmol/L with whole milk (P < or = 0.001); mean low-density-lipoprotein-cholesterol concentrations were 2.64 and 2.96 mmol/L, respectively (P < or = 0.001). Mean apolipoprotein B decreased with skim milk and increased with whole milk (P < or = 0.05). No statistically significant differences were observed for plasma high-density lipoprotein-cholesterol, triglyceride, apolipoprotein A-I, or fatty acids. Substitution of skim milk for whole milk may decrease the risk of coronary heart disease.