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PubMed1986

Environmental factors and cancer mortality in Italy: correlational exercise.

Mortality rates for 21 cancer sites in 20 Italian regions have been correlated with several economic and dietary variables (including alcohol and coffee consumption), patterns of cigarette smoking and reproductive habits. In both sexes, a large number of strong correlations emerged, the most notable ones being the strong positive coefficients between cigarettes sold in the early 1950s and lung cancer mortality in middle-aged males in the early 1970s, between gross internal product or meat consumption and cancer of the intestines in both sexes, between total per caput consumption and cancer of the prostate and between mean age at first birth, gross internal product and milk consumption and cancer of the breast. Cancer of the ovary was positively correlated with mean age at the first birth, and negatively with average number of births. Among the unexpected correlations observed, the most remarkable ones were the strong positive coefficient between skin cancer mortality and latitude (which can however be explained in terms of different constitutional characteristics of skin color in various Italian regions), and the pattern of coefficients emerging for gastric cancer, showing positive correlations with gross internal product or meat and negative ones with bread, pasta or fish. These and other results (including the analysis of several first-order partial correlation coefficients) are discussed with regard to their limitations and major points of interest, and in comparison with similar studies conducted on different populations.

Adult↗
PubMed1982

Risk factors for breast cancer in women in northern Alberta, Canada, as related to age at diagnosis.

A population-based case-control study involving interviews with 577 female breast cancer patients and 826 controls in northern Alberta. Canada, revealed that some determinants of breast cancer varied according to age. Among women under age 45, risk factors included a younger age at menarche, late age at last birth, high parity, and recent use of oral contraceptives. At older ages risk was related to natural as opposed to surgical menopause, late age at first birth, low parity, late age at natural menopause, and tonsillectomy. At all ages there was an increased risk of breast cancer associated with difficulty in conceiving, benign breast disease, not having breast fed, and a history of breast cancer among mothers or sisters. For some variables the age differences were pronounced; the combination of low parity and late age at first birth was associated with a sevenfold increase in breast cancer risk at risk at ages 55-80 but a slight decrease at ages under 45. The effect of tonsillectomy steadily increased with age and represents a new lead, but certain features of the data suggest that the link to oral contraceptives among among younger women and the inverse relation to breast feeding at all ages may not be causal. Even though design limitations (cases interviewed in a different setting from controls) appeared not to influence conclusions, the results may have been subjected to interview bias and thus should be interpreted cautiously.

Adult↗
PubMed2007

Reproductive factors and family history of breast cancer in relation to plasma prolactin levels in premenopausal and postmenopausal women.

Many reproductive factors are associated with breast cancer risk, potentially through a hormonal pathway. The peptide hormone prolactin is essential in mammary development and lactation and may be a link between risk factors and breast cancer. While higher prolactin levels are associated with increased breast cancer risk, few determinants of prolactin levels are known. We conducted a cross-sectional analysis among 1,089 premenopausal and 1,311 postmenopausal women within the Nurses' Health Study (NHS) and the NHS II to examine the associations of reproductive factors, benign breast disease and family history of breast cancer with plasma prolactin levels. Parous women had significantly lower prolactin levels than nulliparous women (parous vs. nulliparous multivariate-adjusted geometric means = 14.1 ng/mL vs. 16.6 ng/mL, p<0.001 for premenopausal and 9.1 vs. 10.1, p=0.04 for postmenopausal women), although levels did not decrease with increasing number of children for either premenopausal (p-trend = 0.23) or postmenopausal (p-trend = 0.07) parous women. Age at first birth was not associated with prolactin levels. The reduction in prolactin levels among parous premenopausal women appeared to attenuate with increasing time since first birth, but the trend was not statistically significant (p-trend = 0.12). Age at menarche, duration of lactation and benign breast disease were not associated with prolactin levels. Family history of breast cancer was associated with significantly higher prolactin levels when compared with no family history among premenopausal (15.9 ng/mL vs. 14.3 ng/mL, p=0.04) but not postmenopausal (p=0.73) women. In conclusion, the associations of parity and family history with breast cancer risk may be mediated, at least in part, by prolactin levels.

Adult↗
PubMed1993

Oral contraceptives and breast cancer in northern Italy. Final report from a case-control study.

To assess the relation between oral contraceptive (OC) use and breast cancer, we analysed data from a case-control study conducted in Northern Italy between 1983 and 1991 on 2,309 cases below age 60 and 1,928 controls admitted to hospital for acute diseases unrelated to OC use and to any of the known or potential risk factors for breast cancer. OC use was reported by 16% of cases and 14% of controls. The multivariate relative risk (RR) for ever vs never use of combination OC was 1.2 (95% confidence interval (CI) 1.0-1.4). However, there was no trend in risk with duration. The RR was elevated for very short use, but declined to 0.8 (95% CI = 0.5-1.0) for five or more years' use. No noteworthy relationship was found for other major measures of OC use, although RR estimates were above unity for women who had stopped use less than 5 years before (RR = 1.5, 95% CI = 1.1-2.0), started use less than 10 years before (RR = 1.3, 95% CI = 1.0-1.9), started when 25 or more years old (RR = 1.4, 95% CI = 1.1-1.7), or after first birth (RR = 1.2, 95% CI = 1.0-1.5). No interaction was observed between OC use and family history of breast cancer, parity and age at first birth. A separate analysis of 373 cases and 456 control below age 40 showed no association with ever use (RR = 0.9, 95% CI = 0.6-1.2).

Adult↗
PubMed2005

Relations of gestational length and timing and type of incomplete pregnancy to ovarian cancer risk.

While the protective nature of parity with respect to ovarian cancer has been well documented, whether a history of incomplete pregnancy affects ovarian cancer risk is uncertain. Data collected from 739 epithelial ovarian cancer cases and 1,313 community controls in the Delaware Valley from 1994 to 1998 were used to evaluate the relation between gestational length and timing of first induced or spontaneous abortion and ovarian cancer risk. Incomplete pregnancy was not associated with ovarian cancer among nulliparous women or among ever-pregnant women either before or after adjustment for relevant confounders (for nulliparous women, odds ratio (OR) = 1.12, 95% confidence interval (CI): 0.66, 1.89; for ever-pregnant women, OR = 0.95, 95% CI: 0.76, 1.18). Among unigravid women, one full-term pregnancy was more protective than an incomplete pregnancy (adjusted OR = 0.29, 95% CI: 0.15, 0.57). These results were independent of the type of pregnancy loss. Among ever-pregnant women, a spontaneous abortion before a first birth provided significant protection (adjusted OR = 0.47, 95% CI: 0.30, 0.75), while no significant effect was found for an induced abortion prior to a first birth (adjusted OR = 0.80, 95% CI: 0.44, 1.47). These data do not support an independent association between incomplete pregnancies, either spontaneous or induced, and ovarian cancer risk.

Abortion, Induced↗
PubMed2004

Pesticide exposure and risk of breast cancer: a nested case-control study of residentially stable women living on Long Island.

We conducted a nested case-control study of women in the New York State cohort who lived on Long Island. We estimated the historical environmental exposure to pesticides in 105 women diagnosed with breast cancer between 1980 and 1992 and 210 age and race-matched controls in this cohort of long-term residentially stable women who completed a short mailed questionnaire in 1980. Prior agricultural land use was assessed from aerial photographs taken in 1947 and 1950. Pesticides detected in drinking water were estimated from measures taken between 1977 and 1992. Geographic information system software was used to calculate the distance between residences and hazardous waste sites (HWS) containing pesticides. We found an increased breast cancer risk for women residing within 1 mile of HWS containing organochlorine pesticides (odds ratio [OR]=2.8; 95% confidence interval [CI], 1.1-7.1), after adjusting for other risk factors. A significant interaction was shown for women residing on land that was previously used for agriculture and women who were either nulliparous or had an older age at first birth (> or =26 yr old), compared to women who did not live on previously agricultural land and with a younger age (<26 yr old) at first birth (OR=6.4; 95%CI, 2.2-18.2). Study power was limited and confidence intervals were wide. Our findings suggest that exposure to pesticides in the environment needs to be more comprehensively investigated in relation to breast cancer risk.

Adult↗
PubMed1985

A model of growth with first-order birth and death rates.

This paper describes the derivation, behavior, and application of a model of growth based on elementary kinetic considerations. The model is based on an abbreviated version of the cell cycle in which first-order kinetics govern both production in a growing fraction and loss from the resting fraction of a cell population. Transition between the resting and growing fraction is assumed. The model is derived in the form of a first-order ordinary differential equation with a simple general form, but no closed form solution. Model behavior is examined analytically at equilibrium, in a limiting case, and qualitatively by numerical integration. Because of the simplicity of the underlying assumptions, the model parameters have direct biological interpretations and simple units. Examples of model fitting to data are given, including a direct comparison to the Gompertz growth law.

Animals↗
PubMed2003

Demography, female life history, and reproductive profiles among the chimpanzees of Mahale.

Demography provides critical data to increase our understanding of the evolution, ecology, and conservation of primate populations. The chimpanzees of the Mahale Mountains National Park, Tanzania, have been studied for more than 34 yr on the basis of individual identification and standardized attendance records. From this long-term study, we derived the following demographic data: The major cause of death was disease (48%), followed by senescence (24%) and within-species aggression (16%). Fifty percent of Mahale chimpanzees died before weaning. The median ages of female life history variables were: first maximal swelling, 10.0 yr (n = 5); emigration, 11.0 yr (n = 11); and first birth, 13.1 yr (n = 5). The median period of adolescent infertility was 2.8 yr (n = 4) when calculated from the age at immigration to that at first birth. Female fecundity was highest between 20 and 35 yr of age, with an annual birth rate of 0.2. Twenty-six females that were observed from a young age (10-13 yr) to death at various ages (15-40 yr) gave birth to an average of 3.9 and weaned an average of 1.4 offspring. Twenty-five females that were observed from middle age (18-33 yr) to death in older age (31-48) gave birth to an average of 2.7 and weaned an average of 2.0 offspring. The post-reproductive lifespan for female chimpanzees was defined as the number of years that passed from the year when the last offspring was born to the year when the female died, minus 5. Twenty-five percent of old females had a post-reproductive lifespan. The interbirth interval after the birth of a son (x = 72 mo) tended to be longer than that after the birth of a daughter (x = 66 mo). The extent of female transfer, which is a rule in chimpanzees, is influenced by the size and composition of the unit group and size of the overall local community.

Age Factors↗
PubMed1999

Correlates of hysterectomy among African-American women.

Hysterectomy is the second most common surgery performed on US women. Baseline data from a large study of African-American women were used to examine correlates of premenopausal hysterectomy. Analyses were conducted on participants aged 30-49 years; 5,163 had had a hysterectomy and 29,787 were still menstruating. Multiple logistic regression was used to compute prevalence odds ratios for the association of hysterectomy with various factors. Hysterectomy was associated with region of residence: Odds ratios for living in the South, Midwest, and West relative to the Northeast were 2.63 (95% confidence interval (CI): 2.38, 2.91), 2.02 (95% CI: 1.81, 2.25), and 1.89 (95% CI: 1.68, 2.12), respectively. Hysterectomy was inversely associated with years of education and age at first birth: Odds ratios were 1.96 (95% CI: 1.74, 2.21) for < or =12 years of education relative to >16 years and 4.33 (95% CI: 3.60, 5.22) for first birth before age 20 relative to age 30 or older. Differences in the prevalence of major indications for hysterectomy did not explain the associations. This study indicates that the correlates of hysterectomy among African-American women are similar to those for White US women. The associations with geographic region and educational attainment suggest that there may be modifiable factors which could lead to reduced hysterectomy rates.

Adult↗
PubMed1991

Reproduction following treatment for childhood leukemia: a population-based prospective cohort study of fertility and offspring.

Of all children diagnosed with leukemia in Denmark, Finland, Iceland, Norway, and Sweden, 981 had discontinued therapy before 1985 and had been followed up annually after cessation of therapy. Progeny was registered and fertility evaluated among survivors who passed age 18 years without a relapse (n = 299). By April 1989, 48 offspring were registered, one of whom had congenital anomalies. This was no more than expected from the incidence of birth defects in the general population. No childhood malignancies or genetic diseases have so far been diagnosed in the progeny. In the study group, none of the 19 female and 8 male survivors of myeloid leukemias had become parents, and only 4 fathers were reported among the 131 male survivors of acute lymphoblastic leukemia (ALL). However, 23 of the 149 females treated for ALL had delivered 41 children. Fertility was measured as cumulative rates of first birth by maternal age. In a Cox regression analysis, cases who had received prophylactic radiation of the central nervous system (CNS) had a lower first birth rate than those without radiation (rate ratio 0.39, 95% CI 0.15-1.00), indicating that doses of 18-24 Gy to the brain may possibly be a risk factor. By using the Norwegian birth cohort of 1966 as a control group, matching the median year of birth for the study subjects, the group of female ALL survivors as a whole was as likely as the general female population to have given birth up to the age of 23. The first generation of females successfully treated for childhood ALL seems to have a nearly normal reproductive pattern during young adulthood, without increased risk of congenital anomalies in the offspring. However, cranial radiation as CNS prophylaxis may possibly impair subsequent reproduction.

Adolescent↗
PubMed2003

An increased risk of breast cancer after delayed first parity.

BACKGROUND: As delayed childbirth increases for socioeconomic and fertility reasons, its impact on breast cancer risk needs definition. METHODS: From 1975 to 1981, 1307 women with childbirth at >or=40 years of age were identified. They were divided into four groups by estimated first birth median ages (EFBMA): 23, 34, 38, and 41 years, corresponding to previous parity of more than 3, 2 or 3, 1, and zero, respectively. Cancer Registry cross-referencing identified those diagnosed with breast cancer. RESULTS: Breast cancer developed in 39 women. The EFBMA of 41 years carried a relative risk of 3.7, (95%CI: 1.30 to 10.5) compared with age 23. Odds ratio of breast cancer was 1.08 (95%CI: 1.02 to 1.14) with each year older at first birth and 0.79 (95% CI: 0.67 to 0.93) for each additional previous birth. CONCLUSIONS: Increased breast cancer risk with advancing maternal age at first childbirth is supported by 3.7 relative risk in women with an EFBMA of 41 years compared with those with an EFBMA of 23 years.

Adult↗
PubMed1987

Parity specific perinatal mortality. A longitudinal study based on sibships.

Perinatal mortality in sibships has been examined using the Medical Birth Registry of Norway. Using linear logistic regression, parity specific perinatal mortality in the period 1967-1981 has been analysed, controlling simultaneously for maternal age, year of birth and survival of earlier births. The risk of a perinatal loss was increased by a factor of up to 6.0 following one earlier perinatal loss, and with three earlier losses the increase was 17.0. The general reduction in mortality between the different five year periods varied according to parity and maternal age. No secular reduction in risk, however, was demonstrated in sibships where the first birth died perinatally; for some subgroups of women the risk actually increased between the first and the second five year period. The effect of maternal age changed with parity, being strong in the first birth order, but of no effect either for the third or the fourth birth orders once the perinatal survival of earlier births was controlled for. This study shows the need to take heterogeneity of risk between women into account in studies of perinatal loss; the overall improvement in perinatal mortality does not apply to every woman. As care improves, perinatal losses become less and less random, demonstrated by increased risks of recurrence.

Adolescent↗
PubMed2006

Do breast cancer risk factors modify the association between hormone therapy and mammographic breast density? (United States).

OBJECTIVE: To evaluate whether the association between hormone therapy (HT) and breast density differs by levels of breast cancer risk factors. METHODS: We evaluated 80,867 screening mammograms from 39,296 postmenopausal women from Washington State. We estimated odds ratios and 95% confidence intervals for dense breasts (Breast Imaging Reporting and Data System categories 3 "heterogeneously dense" and 4 "extremely dense") compared to fatty breasts (categories 1 "almost entirely fat" and 2 "scattered fibroglandular") among HT users compared to never users. We separately examined former HT use and current HT use by type (estrogen plus progestin therapy (EPT) and estrogen-only therapy (ET)). We stratified the associations by age, BMI, race, family history, and reproductive and menopausal factors. RESULTS: Current EPT users had a 98% (1.87-2.09) greater odds of having dense breasts and current ET users had a 71% (1.56-1.87) greater odds compared to never users. Current HT users were more likely to have dense breasts if they were older, had more children, or younger at first birth compared to never users; these associations were stronger among EPT users than ET users. CONCLUSIONS: HT, particularly EPT, may reduce protective effects of older age, parity, and younger age at first birth on mammographic density.

Adult↗
PubMed2003

Dual effect of parity on breast cancer risk in African-American women.

BACKGROUND: In the United States, breast cancer incidence is higher among African-American women than among white women before age 45 but lower at older ages. To explore whether differences in childbearing patterns can explain this observation, we assessed the relation of several childbearing variables to breast cancer risk in a large prospective cohort study of U.S. African-American women. METHODS: Black Women's Health Study participants were enrolled in 1995 and were followed by mailed questionnaires every 2 years (in 1997 and 1999). Of the 64,500 women enrolled, 56,725 (88%) completed at least one of the follow-up questionnaires. During 214,862 person-years of follow-up, participants reported 349 breast cancers, of which 128 were among women younger than 45 years and 221 were among women aged 45-70 years. Incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were derived from age-stratified Cox regression models that adjusted for each of the childbearing variables (parity, age at first birth, and time since last birth). RESULTS: Compared with primiparity, high parity was associated with an increased risk of breast cancer among women younger than 45 years (IRR for four or more births = 2.4, 95% CI = 1.1 to 5.1) and a decreased risk among women aged 45 years and older (IRR = 0.5, 95% CI = 0.3 to 0.9). The IRR for late age at first birth compared with early age was 2.5 (95% CI = 1.1 to 5.8) among the younger women and was not elevated among older women. We found no statistically significant association of time since last birth with breast cancer risk among either younger or older women. CONCLUSIONS: Parity has a dual association with breast cancer risk in African-American women; among women younger than 45 years, parity is associated with an increased risk and among women 45 years and older it is associated with a decreased risk. This dual effect may explain some of the observed differences in breast cancer incidence rates among African-American and white women.

Adult↗
PubMed1993

Epidemiology of breast cancer. Findings from the nurses' health study.

BACKGROUND: The epidemiology of breast cancer was reviewed in the context of hormonal, hereditary, histologic, and dietary risk factors. METHODS: Literature review. RESULTS: Late age at menarche and early age at first birth decrease the risk of breast cancer as does an early age at menopause. These risk factors relate to the lifetime exposure of the breast tissue to ovarian hormones. Although an early first birth is associated with a transient increase in the risk of breast cancer, perhaps as a result of the breast's exposure to high levels of hormones before terminal differentiation, in older women, parity is associated with a decreased risk of breast cancer. Among postmenopausal women, obesity is associated with higher levels of estrogens and an increased risk of breast cancer. Within the strata of breast cancer stages at diagnosis, obesity is associated with increased mortality, again supporting the influence of endogenous estrogens on this disease's incidence, recurrence, and survival rates. Consistent with these relationships, current use of estrogen therapy among postmenopausal women is associated with an increased risk of breast cancer. A family history of breast cancer is associated with approximately a two-fold increase in the risk of breast cancer, and this risk is greater if the diagnosis was made when the woman's mother was young, although even a diagnosis in an older mother is associated with an increased risk in her daughters. The follow-up of women with a history of benign breast biopsy results shows that atypical hyperplasia is associated with a fourfold increase in risk compared with a biopsy specimen without proliferative changes. Atypia doubles the risk. These data support the concept of atypia as a precursor lesion for breast cancer and may warrant its use as a marker in further studies. Consistent data from retrospective and prospective studies show a positive association between moderate alcohol intake and the risk of breast cancer. This may reflect the increase in estrogen levels observed among women who consume alcohol. Data from prospective studies do not support a relationship between dietary fat intake and the risk of breast cancer either in premenopausal or postmenopausal women. CONCLUSIONS: Few of these associations offer the potential for intervention to reduce the breast cancer risk.

Adolescent↗
PubMed1985

Reproductive variables as possible confounders in occupational studies of breast and ovarian cancer in females.

In a study of occupational mortality among all females dying at age 20 years or over in British Columbia during the period 1950 through 1978, significantly elevated proportional mortality ratios (PMRs) were seen for breast and/or ovarian cancer among teachers, nurses, office clerks, and sales clerks. Approximately 91% of the female deaths were recorded as occurring among "homemakers." When the PMRs were recalculated for "working women" only (ie., excluding homemakers), most of the excesses in risks for breast and ovarian cancer observed among the four occupational groups disappeared. The authors suggest that the differences in PMR values between all women and working women are due to protective higher parity and lower maternal age at first birth among homemakers as opposed to working women in general. In occupational studies of hormone-related tumors among women, every effort should be made to control for parity level and maternal age at first birth.

Adult↗
PubMedDate not supplied

Reproductive life of Bhoksa women.

The paper discusses the reproductive life of 111 ever-married Bhoksa women. The mean age at marriage for women of all ages among Bhoksas, like other tribal populations, is high, unlike the caste populations. The mean ages at first birth of the pooled sample and of the completed fertility cases suggest late and early marriages of the older and younger generations. The maximum number of marriages occur between 15 and 19 years and of first births between 16 and 20 years. Percentage of reproductive wastage is high in both the lower and higher age groups. Young mothers with low birth orders and older mothers with high birth orders display a high frequency of reproductive wastage. Evidently, both birth order and the age of the mother have effects on reproductive wastage. Average number of children ever born (including stillbirth but not abortion or miscarriage) per mother of all ages is the highest among Bhoksas of all the studied ethnic groups of India. The Bhoksa, like caste populations, show a high number of children ever born per mother of completed fertility. Quite a high masculinity in the secondary sex ratio, like other mongoloid population is noticed. The contribution of mortality component to the Total Index of Opportunity for Selection is more than that of the fertility component. Bhoksas conform to the general low range of net reproductive index, which is however greater than unity, suggesting that they are in a growth stage.

Age Factors↗
PubMed2005

Breast cancer risk among women who start smoking as teenagers.

OBJECTIVE: To examine the effect of smoking on breast cancer risk in a large population-based cohort of women, many of whom started smoking as teenagers. METHODS: We followed 102,098 women, ages 30 to 50 years, completing a mailed questionnaire at recruitment to the Norwegian-Swedish Cohort Study in 1991/1992, through December 2000. We used Cox proportional hazard regression models to estimate relative risk (RR) of breast cancer associated with different measures of smoking initiation, duration, and intensity adjusting for confounding variables. We conducted analyses on the entire study population, among women who had smoked for at least 20 years, among nondrinkers, and separately for each country. RESULTS: Altogether, 1,240 women were diagnosed with incident, invasive breast cancer. Compared with never smokers, women who smoked for at least 20 years and who smoked 10 cigarettes or more daily had a RR of 1.34 (95% CI, 1.06-1.70). Likewise, those who initiated smoking prior to their first birth (1.27, 1.00-1.62), before menarche (1.39, 1.03-1.87), or before age 15 (1.48, 1.03-2.13) had an increased risk. In contrast, women who had smoked for at least 20 years, but started after their first birth, did not experience an increased breast cancer risk. The increased RR associated with smoking was observed among nondrinkers of alcohol, women with and without a family history of breast cancer, premenopausal and postmenopausal women, and in both countries. CONCLUSION: Our results support the notion that women who start smoking as teenagers and continue to smoke for at least 20 years may increase their breast cancer risk.

Adolescent↗