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Biomedical subjects

B MacMahon

Publications and source records attributed to B MacMahon.

At least 55 records · Page 3Linked to original sources
PubMed1984

Age at first birth and breast atypia.

The relation between age at first birth and the occurrence of fibrocystic breast disease of different atypia subtypes was evaluated using data from a cohort study of the health effects of oral-contraceptive use. Multivariate case-control analysis was performed on 218 parous women with biopsied fibrocystic disease and 928 parous controls. Fibrocystic breast disease, as a whole and as atypia subtypes, was found to be unrelated to age at first birth. Furthermore, the estimated effect of age at first birth did not vary from one atypia subtype to another. Women with high parity were found to be at decreased risk of fibrocystic breast disease compared to those with low parity. Age at completion of education, used as an indicator of socioeconomic status, was found to be moderately associated with fibrocystic breast disease. The estimated effect of parity and age at completion of education also did not vary among subtypes. More epidemiologic studies specific to histopathologic classifications of benign breast disease are called for.

Adult↗
PubMed1984

The effect of westernization on urine estrogens, frequency of ovulation, and breast cancer risk. A study of ethnic Chinese women in the Orient and the USA.

In a 10-year incidence survey of breast cancer in the City of Boston, 14 cases in American Chinese women were observed, while approximately 13 were expected on the basis of age-specific incidence in the white population. In Hawaii, on the other hand, while breast cancer incidence rates for ethnic Chinese are approximately three times as high as those of indigenous Chinese populations, data indicate that they are still 35% lower than those of whites in Hawaii or on the US mainland. We have compared estrogen concentrations in the urine of Chinese women in the Orient, Honolulu, and Boston. Levels of estrone (E1) and estradiol (E2) increased greatly from the low to the high risk group. The increase was evident among both the younger (15-19 years) and the older (20-24 years) women, in both follicular and luteal phase specimens. The crude unweighted average increase from Oriental to continental US Chinese was about 38% and 34% for E1 and E2, respectively. On the other hand, levels of E3 decreased from the low-risk to the high-risk group, but the decrease was modest (16%) and not always regular. There were no systematic or significant differences in the frequency of ovulation in the three groups of women. These results are compatible with the hypothesis that high levels of estrone and estradiol are important to breast carcinogenesis. Whether E3 has some additional "protective" effect or is irrelevant is unclear. The data do not support the hypothesis that total urine estrogens (E1 + E2 + E3) are predictive of population groups at high risk for breast cancer and they appear inconsistent with the hypothesis that frequency of ovulation (or anovulation) is an important aspect of breast carcinogenesis.

Adolescent↗
PubMed1984

Oral contraceptive use and fibrocystic breast disease of different histologic classifications.

The relationship between oral contraceptive (OC) use and occurrence of fibrocystic breast disease (FBD) of different histologic classifications was evaluated with data from a cohort study. Biopsy specimens from 232 women with FBD were classified into different atypia categories. In 96 matched pairs of OC users and nonusers, atypia scores were lower in users than in nonusers. Women without breast diseases (500 OC users and 500 nonusers) were sampled from the original cohort to form a two-stage "anamorphic" study with the 232 cases of FBD. The previously shown inverse association between OC use and FBD occurrence was present and increased with increased length of OC use. However, the "protective effect" of OC use did not vary for different histologic classifications of FBD. The findings from both paired and anamorphic analyses of the data are not consistent with the hypothesis that the use of OC is associated with decreased frequency only of FBD with minimal epithelial atypia.

Adult↗
PubMed1983

Age at any birth and breast cancer risk.

In an effort to assess the relative importance of age at first birth, age at subsequent births, and total parity to the occurrence of breast cancer, reproductive data from 4,225 women with breast cancer and 12,307 hospitalized women without breast cancer were analyzed by a multiple logistic regression model. Age at first birth was confirmed to be the most important reproductive risk indicator; it was associated with a 3.5% increase of relative risk for every year of increase in age at first birth (the 95% confidence interval of this estimate was 2.3 to 4.7% increase per year). However, age at any birth after the first was also an independent and statistically significant risk indicator; it was associated with a 0.9% increase of relative risk for every year of increase in age at any (and every) birth (the 95% confidence interval of this estimate was 0.4 to 1.5% increase per year). There is evidence that the age of approximately 35 years represents for every birth a critical point; before this age any full-term pregnancy confers some degree of protection; after this age any full-term pregnancy appears to be associated with increase in breast cancer risk. The effect of parity is determined by the age of occurrence of the component pregnancies. While most pregnancies occur under the age of 35, the distribution varies from population to population, and this may account for the differences between populations in whether or not a protective effect is seen for births after the first, and if it is seen, its extent.

Adolescent↗
PubMed1983

Obesity, serum cholesterol, and estrogens in premenopausal women.

Creatinine-adjusted levels of estrone, estradiol, and estriol were determined in luteal phase urine specimens of 200 premenopausal women from rural areas of Greece. The relation of each estrogen to height, weight, obesity index, and serum cholesterol was studied by multiple regression, controlling for age, age at menarche, and ovulation status (ovulation, anovulation, undetermined). No consistent relation between any of the somatometric variables and any of the urine estrogens emerged from the statistical analysis, but among older women (30-40 years old) both estrone and estradiol were positively associated with serum cholesterol (p less than 0.05). The data provide no support for the hypothesis that the relationship between body weight and breast cancer risk is mediated through an influence of body weight on estrogen levels--at least in premenopausal women. On the other hand the data on serum cholesterol levels are consonant with the idea that qualitative aspects of nutrition may affect breast cancer risk among older (e.g., postmenopausal) women.

Adolescent↗
PubMed1983

Urine estrogens, frequency of ovulation, and breast cancer risk: case-control study in premenopausal women.

Urine specimens from 94 premenopausal women with breast cancer and from 70 control women have been compared with respect to concentration of the three major estrogen fractions and to frequency of ovulation as assessed by urine pregnanediol. The probability of anovulation (0.14 in the breast cancer patients and 0.09 among the controls) was not significantly higher among the women with breast cancer (P approximately 0.30). However, there was a positive association between urine estrogen concentration and breast cancer risk. The association was statistically significant (P less than 0.05) for each of the three estrogens measured and in both the follicular and the luteal phases of the menstrual cycle; the relative risk increased from 1 in the referent category (less than 5 micrograms estrogen/g creatinine) to about 3 in the highest category (greater than or equal to 15 micrograms estrogen/g creatinine). The association between urine estrogens and breast cancer risk was consistently stronger when the comparison was restricted to specimens collected in menstrual cycles during which ovulation occurred.

Breast Neoplasms↗
PubMed1982

Risk factors for cancer of the pancreas.

The descriptive epidemiology of cancer of the pancreas is hampered by the difficulty of differential diagnosis and the variation in diagnostic expertise and resources around the world. The condition is a disease of the elderly and there are few patients under 40 years of age. The disease is somewhat more common in American blacks than in whites. Two populations of Polynesian origin--Maoris and Hawaiians--show high incidence rates, especially in males. Geographic variation is not striking and is difficult to interpret. The most consistently observed exogenous risk factor is cigarette smoking, the disease being approximately twice as common in heavy smokers as in nonsmokers. In sharp contrast to chronic pancreatitis, pancreatic cancer does not appear to be related to use of alcoholic beverages. Recent observations of association of risk with coffee consumption and with use of decaffeinated coffee require further evaluation.

Adult↗
PubMed1982

Age at menarche, urine estrogens and breast cancer risk.

In 511 nulliparous women aged 15-19 years and 347 aged 30-39, an analysis has been undertaken of the relationship of urine concentrations of the three principal estrogens to age, age at menarche and Quetelet's index of adiposity. The analysis was undertaken by means of multiple regression, controlling for each of the 12 centers from which the data originated, as well as for the other study variables. In the younger women, age was strongly and positively related to concentrations of E1 and E2 and less so to E3. In the age group 30-39, follicular phase specimens showed positive relationships with age for all three fractions but luteal specimens did not. Age at menarche showed inverse relationships to levels of E1 and E2 which were significant in the younger but not in the older age group. The associations of estrogens with Quetelet's index were weak and not statistically significant. The data suggest that women whose menarche occurs early not only have a longer duration of exposure to estrogens during years which are probably important in the initiation of breast cancer but, in addition, their exposures are at a higher level during those years and probably at later ages also. These observations support the hypothesis that the mechanism of the association of early menarche with breast cancer risk is via the association of both with estrogen stimulus.

Adipose Tissue↗
PubMed1982

Age at menarche, probability of ovulation and breast cancer risk.

An analysis is undertaken of the frequency of ovulation in 17 groups of women aged 15 to 19 who had been the subjects of other studies. A urine specimen of at least 8 h accumulation had been provided on the 20th or 21st day of a menstrual cycle by 681 women. Analysis is restricted to 431 specimens which had been collected between 11 and 3 days prior to the onset of the subsequent menstrual period. A pregnanediol concentration of less than 1 mg per litre in such a specimen was taken as evidence that the cycle was anovular. The probability of a cycle being anovular was inversely and significantly related to the number of years since menarche, and, with years since menarche held constant, was positively but not significantly associated with age at menarche. This observation indicates that women with early menarche do not have a longer duration of exposure to anovular cycles than do those whose menarche is delayed, and that variation in the duration of exposure to post-menarcheal anovular cycles does not explain the association of breast cancer risk with early age at menarche. The 17 groups of women were classified into four categories according to ethnic origin and breast cancer incidence in the populations from which they derived. Anovular cycles were not more common in the high-risk groups; indeed, the two centers in the lowest risk category had the highest proportion of anovular cycles.

Adolescent↗
PubMed1982

Consumption of alcohol and tobacco and other risk factors for pancreatitis.

Histories of alcohol and tobacco consumption and other potential risk factors were obtained from 98 patients with pancreatitis and 451 comparison patients at 11 large hospitals in Eastern Massachusetts and Rhode Island between 1975 and 1979. The great majority of the patients with pancreatitis had chronic or recurrent disease. From the comparison patients were excluded patients with other diseases of the pancreas and biliary tract and those admitted for disorders known to be associated with smoking or alcohol use. A statistically significant association of pancreatitis with alcohol use was present in males, but not in females. Cigarette use was very strongly associated with pancreatitis in males and less so in females. The associations with alcohol and cigarette use were independent, each retaining significance after adjustment for the other. There was no significant association of risk with coffee consumption in either sex. A history of biliary tract disease was given by 45 per cent of the male and 60 per cent of the female cases. The associations with alcohol use and cigarette smoking did not appear to be restricted either to the patients with or those without a history of biliary tract disease. Chronic or recurrent pancreatitis appears to have different dominant etiologies in males and females.

Adult↗
PubMed1982

Association of breast cancer risk with age at first and subsequent births: a study in the population of the Estonian Republic.

Information on reproductive history was obtained from 362 urban breast cancer patients attending the oncological dispensaries at Tallinn and Tartu, Estonian Republic, and from 694 urban women participating in gynecologic screening programs offered by the same centers. The 2 groups were compared by means of Mantel-Haenszel and logistic regression procedures to estimate age-adjusted odds ratios. Women whose first birth occurred before 20 years of age had a breast cancer risk less than one-third the risk of nulliparous women. Risk increased with increase in age at first birth (AFB) but remained below 1.0 (relative to nulliparae), even in the highest AFB categories. The fertility rate in Estonia during the period of this study was relatively low, which facilitated an evaluation of the effect of births subsequent to the first. After adjustment for AFB, it appeared that in this population subsequent births had a protective effect additional to that conferred by the first birth. Moreover, for women who had only 2 children, the age at the time of birth of the second child was a determinant of that effect. Compared to nulliparous women, the breast cancer odds ratio for uniparous women who had their child before age 25 was 0.62, and the ratio for duoparous women who had both their children under that age was 0.18. Neither lactation nor menarche was a risk factor for breast cancer in this pouplation.

Adult↗