A healthier lifestyle mitigated the impact of genetic factors on the risk of thyroid cancer, in a study based on data from more than 260,000 individuals.
Thyroid cancer has increased globally in recent years and ranks 9th among 36 cancers worldwide, at a considerable cost to health care systems, wrote Xiuming Feng of Guangxi Medical University, Nanning, Guangxi, China, and colleagues.
Both genetic and lifestyle factors are related to thyroid cancer; previous research suggests a heritability of about 50%, but data on the impact of modifiable lifestyle factors on thyroid cancer are limited, the researchers said.
In a prospective cohort studyin JAMA Network Open, the researchers used data from the UK Biobank and recruited adults aged 40-69 years during March 2006–October 2010. The final study population included 264,956 individuals of European descent. The median age of the participants was 57 years, and 52% were women.
Data on lifestyle behaviors were collected using interviews and questionnaires. The researchers constructed a total lifestyle score based on five variables: diet, physical activity, weight, smoking, and alcohol consumption. Each variable was assigned a score of 0 or 1, with 1 being favorable lifestyle behavior. Lifestyle was divided into three categories: unfavorable (scores 0-1), intermediate (score 2), and favorable (scores 3-5).
Each individual’s polygenic risk score (PRS) was categorized as low, intermediate, or high based on a meta–genome-wide association study of three cohorts.
The main outcome was the development of thyroid cancer.
The researchers identified 423 incident thyroid cancer cases over a median follow-up of 11.1 years.
Overall, higher PRSs were significantly associated with thyroid cancer (hazard ratio, 2.25; 95% confidence interval [CI], 1.91-2.64; P < .00001) as was an unfavorable lifestyle score (HR, 1.93; 95% CI, 1.50-2.49; P < .001 for trend).
An unfavorable lifestyle was significantly associated with thyroid cancer in the highest PRS group, and individuals with high PRS and unfavorable lifestyle had a nearly fivefold increased risk of thyroid cancer (HR, 4.89; 95% CI, 3.03-7.91; P < .001). By extension, “Adherence to a healthier lifestyle could decrease the incidence of thyroid cancer in individuals with a higher PRS,” the researchers wrote in their discussion.
The findings were limited by several factors, including the availability of only baseline lifestyle data, and lack of data on iodine intake, radiation exposure, experience, and family history, the researchers noted. Other limitations include the potential lack of generalizability to populations other than the individuals of European descent in the current study, they said.
However, the study is the first known to address the association among lifestyle, genetic factors, and risk of thyroid cancer, and was strengthened by the large study population, and the results suggest that lifestyle interventions may help reduce the risk of thyroid cancer in those with a genetic predisposition, they concluded.