Body fatness at a young age, body fatness gain and risk of breast cancer: systematic review and meta‐analysis of cohort studies

Abstract

Higher body fatness in adulthood has been consistently associated with an increased risk of postmenopausal breast cancer, as well as a tendency towards a lower risk of premenopausal breast cancer. However, the association between body fatness at a young age (≤30 years), body fatness gain and the risk of breast cancer is less defined. PubMed and Web of Science databases were searched to identify relevant publications. Risk estimates with 95% confidence intervals from each study were transformed into a continuous variable for each 5 kg m increase in body mass index (BMI) and were pooled under a random-effects model. Each 5 kg m increase in BMI was significantly associated with a 14%, 12% and 17% lower risk of breast cancer later in life among all women, premenopausal women and postmenopausal women, respectively. Significant heterogeneity and publication bias were observed. The results remained unchanged after the trim and fill method was applied to correct the bias. Each 5 kg m increase in BMI from a young age until cohort entry was significantly associated with a 13% and 14% higher risk of breast cancer in all women and postmenopausal women, respectively. In summary, higher body fatness at a young age may have a protective role in the later development of breast cancer in both premenopausal and postmenopausal women. However, this potential benefit should not be overemphasized, as our findings suggest that increased body fatness gain from a young age is positively associated with postmenopausal breast cancer risk. These findings further justify the need to maintain a steady weight throughout life.

Body fatness at a young age and risks of eight types of cancer: systematic review and meta‐analysis of observational studies

“…Taken together, the cumulative epidemiological evidence suggests that body fatness at a young age is positively linked with at least 11 types of cancer (Table 1), which are also known to be associated with excess body fatness in middle and late adulthood (1). However, an inverse association was observed between higher body fatness at a young age and breast cancer risk (4). Our findings of a positive association between higher body fatness at young age and subsequent cancer risks may have implications for future cancer incidence, particularly obesity-related cancer, given that overweight and obesity in childhood and adolescence continue to rise around the world (85).…”

“…Taken together, the cumulative epidemiological evidence suggests that body fatness at a young age is positively linked with at least 11 types of cancer (Table ), which are also known to be associated with excess body fatness in middle and late adulthood . However, an inverse association was observed between higher body fatness at a young age and breast cancer risk .…”

“…Both the summary RRs of the eight cancers investigated in the present meta‐analysis and the summary RRs for five cancer types, based mainly on recent meta‐analyses , are summarized in Table . Each 5 kg m −2 increase in BMI at a young age was associated with significantly increased risks of DLBCL (RR 1.21, 95% CI 1.09, 1.35; Figure S1), oesophageal adenocarcinoma (RR 1.88, 95% CI 1.37, 2.57; Figure S2), gastric cardia cancer (RR 1.59, 95% CI 1.15, 2.21; Figure S3), hepatocellular carcinoma (RR 1.31, 95% CI 1.13, 1.51; Figure S4), multiple myeloma (RR 1.23, 95% CI 1.15, 1.30; Figure S5), pancreatic cancer (RR 1.17, 95% CI 1.11, 1.24; Figure S6), renal cell cancer (RR 1.22, 95% CI 1.16, 1.28; Figure S7) and thyroid cancer (RR 1.12, 95% CI 1.07, 1.17; Figure S8).…”

“…The meta-analyses (2,3) by Aune et al reported that each 5 kg m À2 increase in body mass index (BMI) in young adulthood was associated with 45% and 12% higher risks of endometrial and ovarian cancers, respectively. By comparison, our recent meta-analyses (4,5) showed that higher body fatness at a young age was positively associated with colorectal cancer risk but inversely associated with the risks of premenopausal and postmenopausal breast cancer. In contrast, higher body fatness at a young age was not associated with the risk of prostate cancer later in life (6).…”

Risk Models for Breast Cancer and Their Validation

“…Other factors are known to affect the risk of breast cancer, but most have some difficulties for inclusion in a relatively simple model. Using weight change from age 20 or weight at a young age in addition to current weight does appear to improve risk assessment to some extent [36], but requires accurate recall of previous weight. Alcohol consumption is a well documented risk factor [34], but underestimation of consumption is well known and it is not clear how best to allow for this.…”