Reproductive and Hormonal Factors and Thyroid Cancer Risk: Pooled Analysis of Prospective Cohort Studies in the Asia Cohort Consortium

Given the female predominance of thyroid cancer, particularly in the reproductive age range, female sex hormones have been proposed as an etiology; however, previous epidemiological studies have shown conflicting results. We conducted a pooled analysis using individual data from nine prospective cohorts in the Asia Cohort Consortium to explore the association between 10 female reproductive and hormonal factors and thyroid cancer risk. Using Cox proportional hazards models, cohort-specific hazard ratios (HR) and 95% confidence intervals (CI) were estimated and then pooled using a random-effects model. Analyses were stratified by country, birth years, smoking status, and body mass index, and thyroid cancer risk based on age of diagnosis was also examined. Among 259,649 women followed up for a mean of 17.2 years, 1,353 incident thyroid cancer cases were identified, with 88% (n = 1,140) being papillary thyroid cancer. Older age at first delivery (≥26 vs. 21-25 years) was associated with increased thyroid cancer risk (P-trend = 0.003; HR = 1.16; 95% CI, 1.03-1.31), particularly when diagnosed later in life (≥55 vs. < 55 years; P-trend = 0.003; HR = 1.19; 95% CI, 1.02-1.39). Among younger birth cohorts, women with more number of deliveries showed an increased thyroid cancer risk [P-trend = 0.0001, HR = 2.40; 95% CI, 1.12-5.18 (≥5 vs. 1-2 children)], and there was no substantial trend in older cohorts. Distinct patterns were observed for the number of deliveries and thyroid cancer risk across countries, with a significant positive association for Korea [P-trend = 0.0008, HR = 1.89; 95% CI, 1.21-2.94 (≥5 vs. 1-2 children)] and nonsignificant inverse associations for China and Japan. Contextual and macrosocial changes in reproductive factors in Asian countries may influence thyroid cancer risk. Prevention Relevance: This analysis of prospective cohort studies across three Asian countries highlights that older age at first birth is linked to increased thyroid cancer risk. As women delay motherhood, understanding these trends is vital for public health strategies addressing reproductive factors influencing thyroid cancer risk in these populations.

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Journal
Cancer Prevention Research
Published
2025-01-22
DOI
https://doi.org/10.1158/1940-6207.capr-24-0330
Primary Topic
Thyroid Cancer Diagnosis and Treatment
Type
article
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article

Reproductive and Hormonal Factors and Thyroid Cancer Risk: Pooled Analysis of Prospective Cohort Studies in the Asia Cohort Consortium

Eiko Saito, Melissa A. Merritt, Habibul Ahsan, Seiki Kanemura et al.
Cancer Prevention Research
Thyroid Cancer Diagnosis and Treatment
article

Reproductive and Hormonal Factors and Thyroid Cancer Risk: Pooled Analysis of Prospective Cohort Studies in the Asia Cohort Consortium

Eiko Saito, Melissa A. Merritt, Habibul Ahsan, Seiki Kanemura, Atsushi Hozawa, Md. Shafiur Rahman, Paolo Boffetta, Sayada Zartasha Kazmi, You‐Lin Qiao, Aesun Shin, Takashi Kimura, Shoichiro Tsugane, Jeongseon Kim, Daehee Kang, Akiko Tamakoshi, Sarah Krull Abe, Md. Rashedul Islam, Ryoko Katagiri, Ritsu Sakata, Keitaro Matsuo, Norie Sawada, Ji‐Yeob Choi, Yumi Sugawara, Manami Inoue, Xiao‐Ou Shu, Hui Cai, Sue K. Park, Nathaniel Rothman, Wei Zheng, Sooyoung Cho, Kee‐Seng Chia
article en

Abstract

Given the female predominance of thyroid cancer, particularly in the reproductive age range, female sex hormones have been proposed as an etiology; however, previous epidemiological studies have shown conflicting results. We conducted a pooled analysis using individual data from nine prospective cohorts in the Asia Cohort Consortium to explore the association between 10 female reproductive and hormonal factors and thyroid cancer risk. Using Cox proportional hazards models, cohort-specific hazard ratios (HR) and 95% confidence intervals (CI) were estimated and then pooled using a random-effects model. Analyses were stratified by country, birth years, smoking status, and body mass index, and thyroid cancer risk based on age of diagnosis was also examined. Among 259,649 women followed up for a mean of 17.2 years, 1,353 incident thyroid cancer cases were identified, with 88% (n = 1,140) being papillary thyroid cancer. Older age at first delivery (≥26 vs. 21-25 years) was associated with increased thyroid cancer risk (P-trend = 0.003; HR = 1.16; 95% CI, 1.03-1.31), particularly when diagnosed later in life (≥55 vs. < 55 years; P-trend = 0.003; HR = 1.19; 95% CI, 1.02-1.39). Among younger birth cohorts, women with more number of deliveries showed an increased thyroid cancer risk [P-trend = 0.0001, HR = 2.40; 95% CI, 1.12-5.18 (≥5 vs. 1-2 children)], and there was no substantial trend in older cohorts. Distinct patterns were observed for the number of deliveries and thyroid cancer risk across countries, with a significant positive association for Korea [P-trend = 0.0008, HR = 1.89; 95% CI, 1.21-2.94 (≥5 vs. 1-2 children)] and nonsignificant inverse associations for China and Japan. Contextual and macrosocial changes in reproductive factors in Asian countries may influence thyroid cancer risk. Prevention Relevance: This analysis of prospective cohort studies across three Asian countries highlights that older age at first birth is linked to increased thyroid cancer risk. As women delay motherhood, understanding these trends is vital for public health strategies addressing reproductive factors influencing thyroid cancer risk in these populations.

Cancer Prevention ResearchVol. 18(4)
Hitotsubashi University (JP), The University of Sydney (AU), Shizuoka University (JP), Seoul National University (KR), Osaka Prefecture University (JP), National University of Singapore (SG), Chicago Department of Public Health (US), Chinese Academy of Medical Sciences & Peking Union Medical College (CN), Tohoku University (JP), Sapporo University (JP), Hokkaido University (JP), Radiation Effects Research Foundation (JP), Peking Union Medical College Hospital (CN), New Generation University College (ET), Hamamatsu University School of Medicine (JP), University of Chicago (US), National Institute of Biomedical Innovation, Health and Nutrition (JP), National Cancer Centre Japan (JP), National Cancer Center (US), Tohoku University Hospital (JP), National Center for Global Health and Medicine (JP), National Cancer Center (KR), Prevention Group (US), Aichi Cancer Center (JP), National Cancer Institute (US), National University Health System (SG), Hokkaido Institute of Public Health (JP), National Cancer Research Institute (GB), Stony Brook University (US), Nagoya University (JP), The University of Tokyo (JP), International University of Health and Welfare (JP), Vanderbilt University Medical Center (US), University of Bologna (IT), Cancer Council NSW (AU)
Good health and well-being
Openalex Percentile: Top 98%
Thyroid Cancer Diagnosis and Treatment
DOIOpen Access PDFOpenAlex
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