Oral contraceptive use at a young age and the risk of breast cancer: an Icelandic, population-based cohort study of the effect of birth year

Tryggvadóttír, Laufey; Tulinius, Hrafn; Gudmundsdottir, Gudny

doi:10.1038/bjc.1997.23

Cited by 18 publications

(13 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A previous Icelandic study focusing on OC use at young ages and therefore using information given at the first visit to the CDC and only from birth cohorts who had the possibility of exposure to OCs from an early age, indicated a dose-response relationship between breast cancer risk and duration of OC use in young users. 29 The present study group was stratified according to age at diagnosis with cutting points Ͻ40, 40 -55 and Ͼ55 years at diagnosis, where the oldest group represented women diagnosed at postmenopausal ages. The data were also analyzed with stratification according to menopausal status, giving similar results except that this did not allow for investigating separately women diagnosed under the age of 40.…”

Section: Discussionmentioning

confidence: 99%

Breast cancer risk factors and age at diagnosis: An Icelandic cohort study

Tryggvadóttír

Tulinius

Eyfjörd

et al. 2002

Intl Journal of Cancer

View full text Add to dashboard Cite

An increasing number of studies indicates that the strength and even direction of association between breast cancer and established risk factors differ according to the woman's age when she develops the disease. This was studied in the setting of a population based cancer registry using a databank with information on age at menarche, parity, age at first birth, oral contraceptive (OC) use, lactation, height and weight. From a cohort of 80.219 women attending population-based cervical and breast cancer screening in Iceland, 1120 cases were identified, aged 26 -90 years at diagnosis and 10,537 controls, individually matched to the cases on birth year and age when attending. Information given at last visit before diagnosis was used in the analysis, applying conditional logistic regression. Odds ratios and statistical strength of relationships varied according to age at diagnosis for age at first birth, number of births, duration of lactation, height and weight. The decreased risk associated with young age at first birth and increasing duration of breast feeding became less pronounced with advancing age at diagnosis. A reduced risk associated with an increasing number of births was not detected in women diagnosed under the age of 40. An increased risk associated with giving first birth after 30 years of age was mainly detected in women who had only given 1 birth and were diagnosed under the age of 40 (OR ‫؍‬ 7.06 95% CI ‫؍‬ 2.16 -23.01). A positive association with height and especially with weight was confined to women diagnosed after the age of 55. The results confirm that age at diagnosis should be taken into account when studying the effects of breast cancer risk factors. © 2002 Wiley-Liss, Inc. Key words: cohort study; breast cancer; risk factors; age at diagnosis; IcelandThe epidemiology of breast cancer has been studied extensively. 1 The risk of breast cancer is positively associated with age at first birth and negatively associated with number of births, age at menarche and duration of breast feeding. 2 Breast cancer risk has been reported to be positively related with height and body mass index (BMI). 3 But studies taking age at diagnosis into account show a more complicated picture. There are several indications that the observed strength and even direction of association between breast cancer and risk factors differ according to age at diagnosis. 4 -9 Results obtained at 2 different points in time in 2 Icelandic studies using the Cancer Detection Clinic (CDC) cohort did also indicate this. Lower relative risks were observed when the effects of age at first birth were investigated at a later point in time. This was attributed to the higher mean age of the cases in the cohort at the time of the second study. 10,11 Those observations underline the importance of taking into account the age of the group studied, as pointed out by Velentgas et al. 9 In the present nested case-control study we investigated the effects of age at menarche, parity, age at first birth, total duration of oral contraceptive (OC) us...

show abstract

Section: Discussionmentioning

confidence: 99%

Breast cancer risk factors and age at diagnosis: An Icelandic cohort study

Tryggvadóttír

Tulinius

Eyfjörd

et al. 2002

Intl Journal of Cancer

View full text Add to dashboard Cite

show abstract

“…23,27,28 Early oral contraceptive use has a modest effect on breast cancer risk in young women. 29,30 Another study showed that there was an odds ratio of 2.39 for Her-2/neu-positive versus Her-2/neu-negative tumors in women younger than 45 years who had taken oral contraceptives. 31 Parity, particularly early age at first full-term pregnancy combined with higher overall parity, has been hypothesized to explain some of the elevated incidence of breast cancer among young African-American women.…”

Section: Hormones and Hormonal Risk Factorsmentioning

confidence: 99%

“…In addition, studies have shown that African-American breast cancer patients have unique BRCA1 gene mutations, that there are no racial differences in polymorphic distributions of CYP17, and that young women have frequent allelic loss at 11q24.1-q25, which is associated with poor survival rates. 23,30,[35][36][37][38][39][40][41][42][43][44][45] …”

Section: Geneticsmentioning

confidence: 99%

Breast cancer among young African-American women

Swanson

Haslam

Azzouz

2002

Cancer

View full text Add to dashboard Cite

BACKGROUND.African-American women younger than age 45 years have a higher risk of incidence and mortality due to breast cancer than other women. The reason for this disparity in risk is not well understood. METHODS.This review summarizes the literature on the topic of breast cancer in young women and presents a summary of a discussion on this topic during a national forum on breast cancer among African-American women. RESULTS.The occurrence of breast cancer among African-American women younger than the age of 45 years has not been well studied. There is a clear and long-term pattern of higher incidence and mortality and poorer survival in this population subgroup. CONCLUSION.Research is needed to understand the reasons for these disparities and to reduce or eliminate them. Studies focused on hormonal factors, genetic factors, diet and obesity, and timely access to state-of-the-art prevention, information, screening, diagnosis, and treatment are likely to produce important new knowledge in this area. Cancer 2003;97(1 Suppl):273-9.

show abstract

“…Some of the later studies concluded that OC use is a risk factor for breast cancer [3-10], or is for some subgroups [11,12], while other studies have not [13-16]. Young women having used the pill for a long time before their first pregnancy have been identified as a potential risk group [6,14,17,18], but currently there are not enough studies to prove or disprove the increased risk of breast cancer [19]. …”

Section: Introductionmentioning

confidence: 99%