[Ecological analysis of the association between dietary factors and thyroid carcinoma incidence based on GBD 2021...

To examine the association between dietary factors and thyroid carcinoma incidence.

Data on thyroid carcinoma incidence and per capita intake of 15 dietary factors in 194 countries and territories from 1990 to 2021 were extracted from the Global Burden of Disease (GBD) 2021 database. At the dietary factor level, collinearity diagnostics were first performed, continuous dietary exposure variables were standardized using Z-scores before model fitting, and Bayesian generalized linear mixed models with a gamma distribution and log link function were fitted using the age-standardized incidence rate of thyroid carcinoma as the outcome to estimate posterior regression coefficients and rate ratios (per one-standard-deviation increase in each dietary exposure). At the dietary pattern level, principal component analysis was used to derive dietary patterns. After calculating and standardizing the dietary pattern scores, the statistical strength of the association between different dietary patterns and the age-standardized incidence rate of thyroid carcinoma was evaluated. Heterogeneity in the associations was further assessed by stratified analyses according to the sociodemographic index (SDI), sex, and age.

From 1990 to 2021, the global age-standardized incidence rate of thyroid carcinoma increased and showed marked regional variation. Incidence remained consistently higher in females than in males, and the age-specific incidence rates increased with age. Analysis of dietary exposure indicated that intake of dietary fiber, legumes, and nuts increased globally, whereas trans fat intake generally declined. Intake patterns of sugar-sweetened beverages and animal-source foods showed pronounced SDI-related differences. Bayesian generalized linear mixed model identified 11 factors significantly associated with the age-standardized incidence rate of thyroid carcinoma. Intake of legumes, fruits, sugar-sweetened beverages, red meat, trans fats, and sodium was positively associated with thyroid carcinoma incidence, whereas intake of nuts, dietary fiber, processed meat, milk, and vegetables was negatively associated with thyroid carcinoma incidence. Three dietary patterns were identified, scores for pattern 1 (characterized by high loadings of red meat, processed meat, sugar-sweetened beverages, and milk) and pattern 2 (characterized by high loadings of fruits, legumes, vegetables, and polyunsaturated fatty acids, accompanied by a moderate loading of sugar-sweetened beverages) were positively associated with thyroid carcinoma incidence. In contrast, the score for dietary pattern 3 (characterized by high loadings of nuts and omega-3 fatty acids) was negatively associated with thyroid carcinoma incidence.

The global increase in thyroid carcinoma incidence may be associated with changes in dietary structure, especially in medium-development countries undergoing nutritional transition.