History of childbearing and colorectal cancer risk in women aged less than 60: An analysis of Swedish routine registry data 1960–1984

Abstract

Data from a computerised linkage between the Swedish Cancer Registry and the Fertility Registry were used to study the influence of reproductive history on the risk of colorectal cancer in women aged less than 60, in the period 1960 to 1984. A "nested" case-control design was used with 1,415 colon cancer cases and 733 rectal cancer cases, and 7,073 and 3,665 age-matched controls, respectively. Conditional logistic regression was employed to study the independent effects of parity, age at first birth and years since last birth on the risk of colorectal cancer. High parity was associated with reduced risk in women older then 50 years at diagnosis, both for the colon as a whole and for colon subsites. Women having had 5 children or more had an odds of colon cancer of 0.44 (95% confidence interval 0.24-0.82) relative to that of nulliparous woman. Contrary to the hypothesis advanced by McMichael and Potter (J. Nat. Cancer Inst., 75, 185-191 [1985]), which predicted a strong protective effect of parity in the proximal compared to the distal colon, we found the reverse. Increasing years since last birth seemed to be associated with a reduced risk of rectal cancer. A significant positive trend with increasing age at first birth was suggested with respect to distal colon cancer and rectal cancer risk. The mutually adjusted effects of the reproductive variables under study were similar to the unadjusted effects. Our data suggest that increasing parity is associated with a decline in risk of colon cancer but not rectal cancer, although the association with colon cancer is restricted to women aged 50 or more. The effects of age at first birth and years since last birth are not consistent or pronounced.

Reproductive History and Risk of Colorectal Adenocarcinoma

“…Some have found an inverse association of old age at first birth, 28 while others have observed a decreased risk of colorectal cancer with earlier age at first birth. 29 Older age at first birth might be generally related with lower parity and vice versa, which was verified in the present study (data not shown). the dissimilar reproductive patterns of adenocarcinoma in the proximal colon and rectum in the present study indicate that the association of sex hormones with colorectal adenocarcinoma might be confounded by lifestyle factors differently for colorectal cancer in different anatomical locations.…”

“…although many previous case-control 9,10,14,15,23,24,[34][35][36][37][38][39][40][41][42][43] or cohort studies 1,2,[11][12][13]16,17,20,23,25,44,45 examined the relation of reproductive factors and risk of colorectal cancer, most did not find associations. to the extent that pregnancy might have long-lasting effects on the hormonal milieu, it is possible that resulting changes in appetite, taste, or physical activities could contribute to the development of colorectal cancer.…”

Does parity affect mortality among parous women?

“…A few studies have shown a positive relationship between the number of deliveries and the overall risk of gastric cancer morbidity, 25 26 although Palli et al 27 could not confirm that. A protective effect of multiparity on colon cancer morbidity has been seen in some studies, 28 although some other studies have failed to find any association between parity and mortality from colorectal cancer. 29 In this study, the risk of accidental death was over twofold among the primiparous women compared with those of the reference group, and there was a clear tendency towards decreasing suicide rates with an increasing number of children.…”

Specific nutritional infections early in life as risk factors for human colon and breast cancers several decades later

“…38 A larger number of case/control studies more uniformly reported a risk reduction of colorectal cancer in multiparous women. [39][40][41][42][43][44][45][46][47][48] It is likely that the concentration of protective sugars produced during the breastfeeding period is high in the milkproducing breasts, but decreases with increasing physical distance from the producing organ. This may explain a somewhat lower rate of colon cancer reduction after multiple breastfeeding periods in comparison to breast cancer.…”