Obesity, Overweight Responsible for 1-in-5 Future Thyroid Cancers in Australia

Maarit Laaksonen, PhD

New research from Australia suggests the ballooning obesity epidemic in the country could contribute to an increase in thyroid cancers over the next decade.

In what investigators are calling the first study of its kind, the pooled cohort study sought to assess the thyroid cancer burden attributable to current levels of overweight and obesity and found excess weight could be a primary driver of nearly 10,000 cases of thyroid cancer from 2021-2030.

“This finding translates to close to 10,000 thyroid cancers in the next 10 years,” said Maarit Laaksonen, PhD, of the School of Mathematics and Statistics University of New South Wales Sydney, in a statement. “Obesity explains 75% of this burden in Australia.”

With previous research demonstrating an association between increase body mass and risk of thyroid cancer, Laaksonen and a team of colleagues sought to evaluate the thyroid cancer burden attributable to current levels of overweight and obesity, with a secondary interest in evaluating associations by sex. Designed as a pooled cohort study leveraging data from 7 unique cohorts, investigators identified a cohort of 367,058 patients, included 431 incident cases of thyroid cancer, for inclusion in the current study.

Using this data with nationally representative estimates of overweight and obesity prevalence from 2017-2018, investigators estimated the Population Attributable Fractions (PAFs) of future thyroid cancers attributable to overweight and obesity from 2021-2030. Investigators noted planned analyses were adjusted for competing risk of death and would also compare PAFs across multiple population subgroups.

Upon analysis, investigators found current trends in prevalence of overweight and obesity contributed to 18.6% (95% CI, 5.2-30.2) of the future thyroid cancer burden, while obesity alone accounted for 13.7% (95% CI, 5.2-21.4) of the future burden. The obesity-attributable thyroid cancer burden among men was 21.4% (95% CI, 2.8-36.5) and 10.1% (95% CI, 0.8-18.6) among women.

“It is still not well understood what causes the sex difference in overweight/obesity-related thyroid cancer risk,” Laaksonen added. “But our findings add evidence to the urgent need to halt and reverse the current global trend in weight gain, especially obesity and especially in men.”

Further analysis suggested 9.9% (95% CI, 1.0-18.1) of thyroid cancers could be avoided if the current obese were overweight instead. Additionally, results indicated the relative attributable burden of overweight and obesity was greater among those who consumed more than 2 alcoholic drinks per day (63.4%) and among those who were not married or co-habiting (33.2%).

This study, “Thyroid cancers potentially preventable by reducing overweight and obesity in Australia: a pooled cohort study,” was published in the International Journal of Cancer.