A case-control study of risk indicators among women with premenopausal and early postmenopausal breast cancer

Abstract

Among 714 premenopausal and 130 postmenopausal breast cancer cases matched with 8440 controls for age in years and menopausal status, risk indicators for breast cancer were similar, although most associations were stronger in the premenopausal women. Compared with nulliparous women, the relative risk (RR) for those with first birth before age 25 years was 0.7 (95% confidence limits [CL] from 0.5 to 0.9) among premenopausal women, and 0.7 (0.4–1.4) for postmenopausal women. In the premenopausal cases, a history of breast cancer in a sister gave a RR of 3.0 (2.1–4.1) and in a mother 1.9 (1.4–2.5), whereas for the postmenopausal women the RRs were 1.4 (0.6–3.1) and 13 (0.6–2.6), respectively. Fibrocystic breast disease was also a significant predictor of subsequent breast cancer in the premenopausal and postmenopausal women. In relation to women having a single birth, premenopausal women with six or more births had a risk of breast cancer of 0.6 (0.4–1.0), which was present even after adjustment for age at first birth.

Absence of association between reproductive variables and the risk of breast cancer in young women in Sweden and Norway

“…A closer view of available data, however, often reveals a pattern of contradictory findings rather than consistent ones. For instance, the duration of breast feeding and the number of children became accepted as proxy variables for age at first birth almost two decades ago (MacMahon et al, 1973;Kelsey, 1979), whereas later evidence indicates that both breast feeding and high parity exert independent protective effects against the development of breast cancer (Tulinius et al, 1978;Adami et al, 1980;Paffenbarger et al, 1980;MacMahon et al, 1982;Brinton et al, 1983;Helmrich et al, 1983;Trapido, 1983;Lipnick et al, 1984;Byers et al, 1985;Pathak et al, 1986;Ewertz & Duffy, 1988;La Vecchia et al, 1987;Layde et al, 1989).…”

“…The results of several studies have pointed to interactions between parity and age (Janerich & Hoff, 1982;Pathak et al, 1986;Negri et al, 1988) or differences between the risk factors operative in pre-and postmenopausal women (Paffenbarger et al, 1980;Helmrich et al, 1983;Lipnick et al, 1984;Byers et al, 1985;McTierman & Thomas, 1986;Brignone et al, 1987;Layde et al, 1989). But there is no agreement as to the details.…”

“…But there is no agreement as to the details. For instance breast feeding has been claimed by some investigators to confer a protective effect before menopause only (Byers et al, 1985;McTierman & Thomas, 1986), whereas others have failed to show any association (MacMahon et al, 1982;Lipnick et al, 1984). Likewise, a significant protective effect of high parity has been reported to be absent (Hunt et al, 1980;McTierman & Thomas, 1986), confined to premenopausal (Lipnick et al, 1984) or post-menopausal (Paffenbarger et al, 1980;Pathak et al, 1986) women, or present irrespective of age (Helmrich et al, 1983;Byers et al, 1985).…”

“…For instance breast feeding has been claimed by some investigators to confer a protective effect before menopause only (Byers et al, 1985;McTierman & Thomas, 1986), whereas others have failed to show any association (MacMahon et al, 1982;Lipnick et al, 1984). Likewise, a significant protective effect of high parity has been reported to be absent (Hunt et al, 1980;McTierman & Thomas, 1986), confined to premenopausal (Lipnick et al, 1984) or post-menopausal (Paffenbarger et al, 1980;Pathak et al, 1986) women, or present irrespective of age (Helmrich et al, 1983;Byers et al, 1985). A first birth at an early age has been found to entail a reduced risk of developing breast cancer only or primarily before menopause (Lipnick et al, 1984;Ewertz & Duffy 1988;Layde et al, 1989), after menopause (Stavraky & Emmons, 1974;Lubin et al, 1982;Byers et al, 1985), or at all ages (Tulinius et al, 1978;Kelsey, 1979;Paffenbarger et al, 1980;Helmrich et al, 1983;Negri et al, 1988;Layde et al, 1989).…”

“…Likewise, a significant protective effect of high parity has been reported to be absent (Hunt et al, 1980;McTierman & Thomas, 1986), confined to premenopausal (Lipnick et al, 1984) or post-menopausal (Paffenbarger et al, 1980;Pathak et al, 1986) women, or present irrespective of age (Helmrich et al, 1983;Byers et al, 1985). A first birth at an early age has been found to entail a reduced risk of developing breast cancer only or primarily before menopause (Lipnick et al, 1984;Ewertz & Duffy 1988;Layde et al, 1989), after menopause (Stavraky & Emmons, 1974;Lubin et al, 1982;Byers et al, 1985), or at all ages (Tulinius et al, 1978;Kelsey, 1979;Paffenbarger et al, 1980;Helmrich et al, 1983;Negri et al, 1988;Layde et al, 1989). A protective effect of late menarche has been shown in premenopausal women (Stavraky & Emmons, 1974;Paffenbarger et al, 1980;Helmrich et al, 1983;McTierman & Thomas, 1986), post-menopausal women (Choi et al, 1978;Byers et al, 1985) and both categories (Kelsey, 1979).…”