Obesity and Risk of Differentiated Thyroid Cancer

A Large-Scale Case-Control Study

Qiao He; Hui Sun; Fang Li; Nan Liang

Disclosures

Clin Endocrinol. 2019;91(6):869-878. 

In This Article

Abstract and Introduction

Abstract

Objective: Recently, the incidence of thyroid cancer as well as obesity has dramatically increased worldwide. Whether obesity contributes to the development of differentiated thyroid cancer (DTC) remains controversial. We evaluated the relationship between anthropometric measurements and DTC risk.

Design/Patients/Measurements: A large frequency-matched case-control study based on hospital data was performed. A total of 10 668 DTC patients and 11 858 controls were enrolled. Body mass index (BMI), body surface area (BSA) and body fat percentage (BF%) were calculated. An unconditional logistic regression model was applied.

Results: The univariate analysis showed a significant increase in DTC risk with increased height, weight, BMI, BSA and BF%. The multivariate analysis also showed a positive relationship. Based on the Chinese BMI (CN-BMI) classification, for women of all ages, the ORs for DTC risk in overweight and obesity were 1.151 (1.037–1277) and 1.292 (1.092–1.528), respectively. For men under 50, the ORs were 1.221 (1.014–1.469) and 1.520 (1.202–1.923), respectively, but the ORs for men over 50 were not significant. Additionally, BSA showed a significant association with DTC risk for both sexes under 50 (P = .02 and P < .001). BF% remained significant only for women under 50 (P = .003). However, for both sexes over 50, neither BSA nor BF% was significantly associated with DTC risk. Based on The World Health Organization BMI (WHO-BMI) classification, for all women and men over 50, the results were consistent with CN-BMI. For men under 50, BF%, but not BMI, showed a significant association with DTC risk.

Conclusion: BMI, BSA and BF% were positively correlated with the risk of DTC, which was potentially affected by age and sex.

Introduction

The incidence of thyroid cancer has increased during the last few decades, possibly due to the increased use of ultrasound and increased screening practice, as well as the availability of other sensitive radiological investigations.[1,2] Recently, evidence has suggested that obesity is a suspected risk factor for differentiated thyroid cancer (DTC).[2,3] Previous epidemiological studies and meta-analyses have demonstrated that obesity is independently associated with an increased incidence of thyroid cancer.[1,4,5] It was also reported that the prevalence of obesity coincided with the increased incidence of thyroid cancer in the United States.[1] Similarly, recent data have shown that China has become the country with the greatest number of obese individuals worldwide and has an increasing rate of thyroid cancer.[6] The prevalence of overweight and obese individuals in China reached 41.2% and 12.9%, respectively, in 2014, with increases of 3.8% and 4.3%[7] since 2000. During the same period, the age-standardized incidence of thyroid cancer in China increased from 2.40/100,000 in 2003 to 13.75/100,000 in 2012, revealing a 4.73-fold increase.[8]

Currently, the relationship between obesity and the risk of DTC is controversial. Some studies showed a positive association, while some showed no significant connection.[9,10] In addition, recent studies mainly focused on Western populations, with few studies performed in Asian populations.[11] It is well known that obesity can be quantified by several indicators. Body mass index (BMI) and body fat percentage (BF%) are widely accepted and applied and can be obtained through simple measurements and calculations.[12,13] Body surface area (BSA), another indicator, is positively proportional to basal metabolism and can reflect the ratio of body fat to nonfat components in individuals with the same BMI.[14] Hence, through retrospective analysis of large-scale case-control data, we evaluated the relationship between obesity indicators (BMI, BF% and BSA) and the risk of DTC to provide new evidence for the epidemiological study of DTC and guide the primary prevention of DTC.

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