Overweight in midlife and risk of cancer in late life: A nationwide Swedish twin study

• Published in: International journal of cancer 2019-05, Vol.144 (9), p.2128-2134
• Main Authors: Bao, Cuiping, Yang, Rongrong, Pedersen, Nancy L, Xu, Weige, Xu, Hui, Song, Ruixue, Qi, Xiuying, Xu, Weili
• Format: Article
• Language: English
• Subjects: Body mass; Body mass index; Body weight; Cancer; cancertwin study; Cervical cancer; Colon cancer; Control data (computers); Ecological risk assessment; Environmental factors; epidemiology; Health risk assessment; Health risks; Liver; Liver cancer; Medical research; midlife overweight; Overweight; population-based cohort; Population-based studies; Regression analysis; Skin cancer; Twin studies; Twins; Uterine cancer
• ISSN: 0020-7136; 1097-0215; 1097-0215
• DOI: 10.1002/ijc.32005

Our study examined whether midlife overweight (body mass index [BMI] ≥25) is associated with late‐life cancer risk and explored the role of genetic and early‐life environmental factors in this association. The study included 14,766 individuals from the Swedish Twin Registry, whose midlife (30–50 years) height and weight were recorded. Information on cancer diagnoses in late life (>65 years) was derived from the National Patient Registry and Cancer Registry. Generalized estimating equation (GEE) models were used to analyze unmatched case–control data (controlled for the clustering of twins within a pair). A co‐twin matched case–control analysis used conditional logistic regression to compare cancer‐discordant twins. Of all participants, 3968 (26.9%) were overweight and 4253 (28.8%) had cancer. In multi‐adjusted GEE models using normal‐weight (BMI 18.5–24.9) participants as the reference group, overweight was related to higher risk of colon cancer (OR 1.36, 95% CI: 1.00–1.84, p = 0.049), liver cancer (OR 2.00, 95% CI: 1.11–3.62), cervix uteri cancer (OR 2.86, 95% CI: 1.19–6.91) and corpus uteri cancer (OR 1.78, 95% CI: 1.14–2.78) but lower risk of nonmelanoma skin cancer (OR 0.77, 95% CI: 0.66–0.90). In conditional logistic regression analysis, these associations were attenuated becoming nonsignificance. The difference in ORs from the unmatched and matched analyses was not significant. In conclusion, midlife overweight is associated with increased risk of late‐life colon, liver and uterine cancer but reduced risk of late‐life nonmelanoma skin cancer. Further investigations are warranted to explore the role of genetic and early‐life environmental factors in these associations. What's new? While overweight and obesity are known risk factors for cancer, the impact of these conditions at midlife on the development of site‐specific cancers after age 65 is uncertain. Here, in a Swedish twin cohort, overweight at ages 30 to 50 was associated with an increased risk of developing colon, liver, or uterine cancer after age 65. Overweight at midlife was also linked, however, to a significant decrease in non‐melanoma skin cancer risk in late life when compared to normal weight individuals. Understanding the degree to which genetic and early‐life environmental factors contribute to these associations requires further investigation.