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Biomedical subjects

R K Ross

Publications and source records attributed to R K Ross.

At least 163 records · Page 9Linked to original sources
PubMed1988

Risk factors for breast cancer in Chinese women of Beijing.

A self-administered questionnaire was completed by 497 Chinese women in Beijing with histologically confirmed breast cancer and by an equal number of age- and neighborhood-matched control women. High body weight (71 + kg) was a risk factor for breast cancer in women aged 50 + (RR = 1.90), but this effect did not quite reach statistical significance. Nulliparity and late age at first birth were associated with an elevated risk of breast cancer. In comparison to parous women who had their first child before age 20, those who delayed this event until after age 29 had an RR of 1.65. The comparable RR for nulliparous women was 3.72. Late age at menopause was a risk factor for breast cancer. The RR for menopause after age 50 compared to menopause before age 45 was 2.16. High parity and long duration of lactation were protective factors against breast cancer. These 2 factors were highly correlated with each other and also with age at first birth. The effect of each on breast cancer risk was somewhat reduced after adjustment for the other two. A personal history of benign breast disease (RR = 3.21) and a family history of breast cancer (RR = 2.17) were also associated with an increased risk of breast cancer.

Adult↗
PubMed1988

Risk factors for breast cancer in Chinese women in Shanghai.

Five hundred thirty-four histologically confirmed incident cases of breast cancer in Chinese women of Shanghai and an equal number of age and sex-matched population controls were interviewed as part of an epidemiological study of breast cancer risk factors. Early age at menarche was positively associated with breast cancer risk whereas early age at first full term pregnancy, high parity, and long duration of nursing were each negatively associated. We found high average body weight to be a risk factor, especially among women over age 60. Use of oral contraceptives after age 45 also was a risk factor, but use in general was not. Personal history of benign breast disease and history of breast cancer in first degree female relatives both increased risk. Multivariate analysis showed that each of these risk (or protective) factors was independently related to breast cancer. In addition to confirming most of the breast cancer risk factors of Western populations in a low risk developing Asian country, this study demonstrates a clear beneficial effect on breast cancer risk of lactation in a population characterized by a long cumulative duration of nursing in the majority of women. Finally, this study supports several other recent reports of a residual and beneficial effect of parity on breast cancer risk after controlling for age at first full term pregnancy.

Abortion, Spontaneous↗
PubMed1988

A case-control study of male breast cancer.

A case-control study was conducted in Los Angeles County, CA, of 75 male breast cancer cases aged 20-74 yr at diagnosis to investigate the role of a number of suspected risk factors. The study involved both interviews and laboratory measurements. Factors under study included fertility and marital history, obesity, alcohol and cigarette consumption, use of drugs known or suspected of causing gynecomastia, family history of breast cancer, history of radiation exposure to the upper body, sex chromatin analysis, serum levels of prolactin, testosterone, estrone, estradiol and sex-hormone-binding globulin, as well as urinary levels of estrone, estradiol, and estriol. Two patients versus no controls tested positive for sex chromatin and were excluded from further analyses. The only statistically significant risk factor identified was greater weight of the cases at age 30; a man who weighed 80 or more kg at age 30 had twice the risk of breast cancer of a man weighing less than 60 kg at that age. Serum estrone levels were positively, and sex-hormone-binding globulin levels were negatively, related to body weight, and we interpret the greater weight of the cases as suggesting that the underlying risk factor is an increased exposure to bioavailable estrogen. None of the differences observed between cases and controls for either the serum or urinary hormone levels was, however, statistically significant and there did not appear to be any large absolute excess of estrogens or deficit of testosterone in the cases. This apparent contradiction may be explained by the fact that there was little difference in weight between the cases and controls at the time of sampling.

Adult↗
PubMed1988

Estrogen replacement therapy and protection from acute myocardial infarction.

As part of a longitudinal study of a southern California retirement community begun in June 1981, 8841 women 44 to 101 years old completed a health survey questionnaire. As of January 1, 1987, 1019 deaths had occurred among these women, who had contributed 40,919 years of follow-up. Women who had used estrogen replacement therapy had a relative risk of death due to all causes of 0.80 compared with women who had never used estrogens (p = 0.0005). Much of this reduced mortality rate was due to a marked reduction in the death rate of acute myocardial infarction among users of estrogen (55 deaths) compared with nonusers (94 deaths; relative risk = 0.59, p = 0.002). This lower acute myocardial infarction death rate was maintained even in the presence of other known risk factors for coronary artery disease. There was no substantial effect of dose or duration of estrogen use on risk, but the relatively small number of deaths limited our ability to estimate these effects accurately. Current users (those who were using estrogen at the time of the initial questionnaire) had a relative risk of 0.47 and past users had a risk of 0.62 compared with women who had never used estrogen (p = 0.003 for trend). A reduced hospitalization rate for acute myocardial infarction was similarly observed for estrogen users compared with nonusers (relative risk = 0.72, p = 0.03).

Adult↗
PubMed1988

Maternal hormone levels in early gestation of cryptorchid males: a case-control study.

A case-control study was conducted to assess maternal hormonal factors associated with increased risk of bearing a cryptorchid son. Serum samples were collected during the first trimester of pregnancy from participants in the US Collaborative Perinatal Study. Twenty-five mothers of normal offspring (controls) were individually matched on medical center, age, parity, weight and length of gestation at the time of sampling to women bearing sons who had a diagnosis of cryptorchidism at one year of age or older. Compared with controls, mothers of cryptorchid sons (cases) had significantly greater percentages of non-protein bound (P = 0.010) and albumin-bound (P = 0.014) estradiol during the first trimester of the index pregnancy. On average, cases had 16% more bioavailable oestradiol than controls. Levels of human chorionic gonadotropin, testosterone, non-protein bound testosterone and sex-hormone binding globulin did not differ between the two groups. The data presented support the hypothesis that cryptorchidism results from elevated maternal oestrogen levels early in pregnancy.

Adult↗
PubMed1988

Vasectomy, cigarette smoking, and age at first sexual intercourse as risk factors for prostate cancer in middle-aged men.

A population-based case-control study was conducted in men aged 60 or less to assess the risk of prostate cancer associated with vasectomy and other factors. Data were obtained from 216 case-control pairs by telephone interviews; this number represented 55% of all eligible cases. The matched pairs relative risk (RR) for vasectomy in ever married men was 1.4 with a 95% confidence interval (CI) of 0.9-2.3. There was a positive association between the number of years since vasectomy and prostate cancer risk (1-sided P = 0.01). Early age at first sexual intercourse was associated with increased prostate cancer risk (age less than 17 vs. 21+, RR = 2.3, 95% CI = 1.3, 4.0) but there were no consistent associations with number of sexual partners or frequency of sexual intercourse. Cigarette smoking was also associated with increased risk of prostate cancer (RR = 1.9, 95% CI = 1.2, 3.0) and there was a positive dose-response relationship with years of smoking (1-sided P = 0.001). We discuss the possible implication of the low response rate on each of these findings. To determine whether the association with vasectomy might have a hormonal basis, we compared levels of testosterone (T) and testosterone binding globulin-binding capacity (TeBG-bc) in 33 of the vasectomized control men with levels in 33 non-vasectomized controls of the same age, weight and height. T levels were higher in vasectomized than in non-vasectomized controls (1-sided P = 0.06). The ratio of T to TeBG-bc (an index of bioavailable T) was 13.5% higher in vasectomized men (1-sided P = 0.03).

Adenocarcinoma↗
PubMed1988

Hormonal factors and risk of ovarian germ cell cancer in young women.

No previous controlled studies of ovarian germ cell tumours have been reported; however the tumour is similar to germ cell testicular cancer in terms of histology, age-specific incidence rates (i.e. highest rates in young adulthood), and secular trends of increasing incidence. The investigation was designed to determine if maternal hormonal factors which have been found to increase the risk of testis cancer in male offspring are also risk factors for the ovarian tumour. The analysis is based on 73 cases diagnosed before age 35 and 138 age-race matched controls. The cases were identified by tumour registries in Los Angeles (1972-84) and Seattle (1974-84) and controls were selected from friends and/or neighbourhood residents. Interviews were conducted on the telephone with mothers of cases and controls. The primary finding was that mother's use of exogenous hormones (including the hormonal pregnancy test, DES or other supportive hormones, and inadvertant use of oral contraceptives after conception) increased risk (Odds ratio, OR = 3.60, 95% CL = 1.2-13.1). Other maternal factors associated with elevated risk were high pre-pregnancy body mass (OR = 2.7, 95% CL = 1.0-7.6), more rapid achievement of regular menstruation after menarche (OR = 1.8, 95% CL = 0.9-3.8), and age at index pregnancy under 20 (OR = 2.8, 95% CL = 1.0-10.7). In conclusion, these results support findings from testis cancer studies regarding a hormonal aetiology for germ cell tumours, and a mechanism by which oestrogen may affect the germ cells is proposed.

Adolescent↗
PubMed1988

Reproductive, genetic, and dietary risk factors for ovarian cancer.

A case-control study of 110 women with ovarian epithelial carcinoma and 220 individually age-matched controls was conducted in Hokkaido, Japan, to identify ovarian cancer risk factors. Both the cases and the matched controls were surveyed either from 1980 to 1981 or from 1985 to 1986. Ovarian cancer risk was increased in single women (p less than 0.01), and in women with a family history of breast, uterine, or ovarian cancer in a mother or sister (p less than 0.001). Conversely, risk was decreased in women who had experienced a livebirth (p less than 0.001), an induced abortion (p less than 0.05), or who had had permanent sterilization by tubal ligation (p less than 0.05). Each of the reproductive factors remained significant when adjusted for each other using logistic regression analysis. The odds ratio for ovarian cancer decreased significantly with increasing number of livebirths (p less than 0.001). Furthermore, a significant negative association between anovulatory periods and ovarian cancer risk was noted (p less than 0.01). No association was observed for any types of contraceptive methods other than tubal ligation, but the prevalence of oral contraceptive use was very low. A significant positive association with daily fish consumption (p less than 0.05) and a marginally significant negative association with daily milk consumption (p = 0.05) were also observed.

Diet↗
PubMed1988

Past and present preferred prescribing practices of hormone replacement therapy among Los Angeles gynecologists: possible implications for public health.

Usual prescribing strategies of hormone replacement therapy for postmenopausal women by Los Angeles area gynecologists, both now and 10 years ago, were investigated by a mail survey. Of the 330 gynecologists who responded, estrogen therapy is currently used as a routine by nearly all (95 per cent), for women both with and without a uterus. Over three-fourths of these physicians favor use of 0.625 mg of conjugated equine estrogen. The estrogen is combined with cyclic progestin therapy, usually 10 mg of medroxyprogesterone acetate, by 86 per cent of gynecologists using estrogen for women with a uterus, and by 47 per cent for women without a uterus. Although conjugated equine estrogens were used widely for both groups of patients 10 years ago, a higher dose generally was preferred. Use of progestin therapy was uncommon (less than 20 per cent) for any postmenopausal patients at that time. Although the most common monthly therapeutic regimen for estrogen/progestin therapy is estrogen for days 1-25 and progestin for days 16-25, there is wide variation in prescribing strategies. We present these findings in the context of the probable effects of estrogen/progestin therapy on various chronic disease outcomes.

Adult↗
PubMed1988

Avoidable nondietary risk factors for cancer.

Smoking cessation has the greatest potential for reducing cancer mortality. Moderate physical activity may prevent colon cancer by modifying bowel peristalsis patterns and may prevent breast cancer by modifying ovulatory frequency. Radiation therapy and the use of certain drugs may increase the risk of some cancers. Liver cancer may be the most preventable major cancer.

Adult↗
PubMed1988

Re-evaluating the role of progestogen therapy after the menopause.

An estrogen-progestogen regimen of hormone replacement therapy has become widely used in recent years, primarily as a means to protect the endometrium from the carcinogenic effects of unopposed estrogen therapy (ERT). In this article, we evaluate the probable effects of this regimen on mortality from endometrial cancer as well as mortality from other chronic diseases. We conclude from this analysis that ERT is to be preferred to combination therapy for postmenopausal women without a uterus, primarily because it is predicted that ERT confers a significantly greater benefit on heart disease risk. In women with a uterus, if progestogens are to be prescribed, they should be given in the lowest possible dose needed to achieve the desired histologic changes in the endometrium, since the predicted loss in heart disease benefit from adding the progestogen is substantial.

Breast Neoplasms↗
PubMed1987

Hyperemesis gravidarum in relation to estradiol levels, pregnancy outcome, and other maternal factors: a seroepidemiologic study.

Two studies were conducted to assess factors associated with increased risk of hyperemesis gravidarum during pregnancy with data and serum samples collected from participants in the Collaborative Perinatal Study. In the case-control study, 419 pregnant women with hyperemesis gravidarum were matched on medical center, date of study registration, and race with 836 pregnant women who did not vomit during the index pregnancy. Younger age, nulliparity, and high body weight were significantly associated with increased risk of hyperemesis. Women with hyperemesis had significantly reduced risk of fetal loss; however, their infants had higher risk of central nervous system malformations. In the second study, first-trimester pregnancy hormones were measured in the serum of 35 women with hyperemesis and 35 control women who were individually matched to cases on age, parity, and medical center. After adjusting for length of gestation, mean levels of total estradiol were 26% higher and mean levels of sex hormone binding-globulin binding capacity were 37% higher in patients with hyperemesis gravidarum than in control subjects. These differences were statistically significant. Although human chorionic gonadotropin concentrations were higher in control pregnancies, the differences were not statistically significant. The average amount of estradiol that was nonprotein bound (adjusted for length of gestation) was also higher in patients than in control subjects. These results are consistent with the hypothesis that elevated estrogen levels are responsible for excessive vomiting in pregnancy.

Adult↗
PubMed1987

Use of preventive care by the elderly.

Use of five early disease detection tests was examined in relation to history of specific chronic disease and other health habits, as part of a cohort study including 11,888 residents of a retirement community in Southern California. Self-reported utilization rates by residents in the year preceding study entry were approximately 90, 30, 60, and 10% for blood pressure measurement, fecal occult blood test, Papanicolaou test, and mammography, respectively. Breast self-examination was practiced by 37% of the women on a regular basis. With the exception of the Pap test and blood pressure check, the majority of the study population did not use preventive procedures at the recommended frequencies. The most important determinants of use of screening tests in this elderly population were previous diagnosis of chronic disease, especially of the disease detected by the test itself, and having a regular physician. These two factors appeared to affect use independently.

Aged↗
PubMed1987

The effects of moderate physical activity on menstrual cycle patterns in adolescence: implications for breast cancer prevention.

Girls who engage in strenuous physical activity are often amenorrheic and have recently been reported to be at a reduced risk of breast cancer. To determine whether moderate amounts of exercise affect menstrual cycle patterns and ovulatory frequency in young postmenarcheal girls, the menstrual cycles and physical activity patterns of 168 high school girls were monitored for a 6 month period. Anovulatory cycles were associated with later age at menarche, fewer elapsed years since menarche and greater levels of energy expended per week in physical activity. After adjusting for age at menarche and years since menarche, there was a significant dose-related trend in the risk of anovular menstrual cycles associated with increasing levels of physical activity (1-sided P = 0.03). Major determinants of average cycle length were weekly average energy expenditure (less than or equal to 750 kcal wk-1 associated with cycles that were on average 2.4 days longer), age at menarche (an increase of 0.7 days per year of age) and race (Asians having cycles about 1.9 days longer than Caucasians). Because a major determinant of breast cancer risk may be the cumulative number of ovulatory cycles, these data suggest that regular participation in moderate physical activity, by reducing the frequency of ovulatory cycles in adolescence, may provide an opportunity for the primary prevention of breast cancer.

Adolescent↗
PubMed1987

Alcohol, physical activity and other risk factors for colorectal cancer: a prospective study.

The aetiology of colorectal cancer was studied in a cohort of 11,888 residents of a retirement community. After four and one-half years of follow-up, 58 male and 68 female incident colorectal cancers were identified. Daily alcohol drinkers experienced nearly a two-fold increase in risk (2 sided P = 0.002). Colorectal cancer was also positively associated with Quetelet's index and inversely associated with avocational physical activity. The results were consistent for both sexes but were statistically significant only for males. With the exception of dietary vitamin C, none of the nutrients under study (i.e., vitamins A and E, dietary fibre, calcium, and beta carotene) showed a significant association with colorectal cancer. An inverse relationship between colorectal cancer and dietary vitamin C was observed in females, but there was no association with either vitamin C from supplements or with total vitamin C intake. Males and females who had 3 or more children showed a significantly reduced risk of colorectal cancer (RR = 0.45, 95% CI = 0.2, 0.9), but those with no children did not show the highest risk.

Age Factors↗
PubMed1987

Cancer of the gastrointestinal tract among Japanese and white immigrants in Los Angeles County.

With the use of age-adjusted incidence rates and proportional incidence ratios, investigators studied the risk of cancer of the stomach and 3 subdivisions of the large bowel in three race-ethnic groups--Spanish surnamed whites, other whites, and Japanese--and compared Los Angeles County native residents, immigrants, and representative "homeland" populations. The risk pattern for each of the four anatomic sites was quite distinctive, suggesting at least four different etiologic complexes. For each site the observed gradients of risk are nearly identical for each sex, usually with risk for immigrants intermediary between that for homeland residents and that for local natives; the differences between race-ethnic groups are consistent with known international patterns. Particularly notable is the contrast between the low risks of cancer of both the sigmoid and the rectum in Japan and the high risks for Japanese immigrants to Los Angeles, which are nearly double those of their U.S. white neighbors. In all instances, and especially for both the upper and lower colon, the influence of the adult environment predominates over that of the early environment. The environmental determinants of stomach cancer do not always appear in inverse correlation with those of colon cancer, since Japanese immigrants to Los Angeles and their descendants are at high absolute and relative risk of both neoplasms. Our findings suggest that patterns of risk in relation to migration are complex and defy simple dietary or other interpretation. Without more information about the impact of migration to the United States on qualitative and quantitative aspects of lifestyle, it is not possible to put forward simple hypotheses that explain all available facts.

California↗
PubMed1987

Case-control studies of prostate cancer in blacks and whites in southern California.

To identify risk factors for prostate cancer and to try to explain the high risk of blacks relative to whites, case-control interview studies of prostate cancer were conducted in both populations in southern California. Both studies included 142 pairs of cases and population controls matched on age. Cases in blacks were identified by the population-based tumor registry of Los Angeles County and cases in whites were identified by a population-based tumor registry of a southern California retirement community. A past history of venereal disease was associated with a high risk of prostate cancer in both populations [relative risk (RR) = 2.3 in whites; RR = 1.7 in blacks]. The result in blacks was statistically significant (P = .03). Black cases tended to have more frequent sexual intercourse than black controls at all ages; the difference became statistically significant for intercourse late in life. Data from controls suggested that, overall, blacks have earlier and more frequent sexual activity than whites, but the two populations were dissimilar in social class characteristics. Fat intake was a risk factor for prostate cancer in both populations, but vitamin A consumption and protein intake were inconsistently related or unrelated to prostate cancer risk. While beta-carotene was not consistently related to risk, there was some indication that in persons with low fat intake, low beta-carotene intake may be associated with high risk. Circumcision was negatively associated with risk in both populations (RR = 0.5 in whites; RR = 0.6 in blacks). These results are discussed in the context of major etiologic hypotheses for prostate cancer.

Black People↗