To analyze and compare the characteristics of comorbidity patterns in skeletal fluorosis patients across different endemic regions, laying the foundation for further research on influencing factors, while providing references for healthcare systems to develop more targeted, effective, and cost-efficient chronic disease management plans for this special population.

This study adopted a cross-sectional design, selecting patients over 40 years old with skeletal fluorosis from Nayong County, Guizhou Province (a coal-burning fluorosis endemic area), Jishan County, Shanxi Province (a water-drinking fluorosis endemic area), and Ruoergai County, Sichuan Province (a tea-drinking fluorosis endemic area) as research subjects. The Apriori algorithm was used to analyze the dataset, and indicators such as the minimum conditional support were set to derive disease association rules. Additionally, Yule’s Q method was applied for systematic cluster analysis, and a dendrogram was drawn to explore the comorbidity patterns of chronic diseases in the elderly.

In the coal-burning type disease area, patients aged over 70 accounted for the highest proportion (43.55%), and the prevalence rates of chronic kidney disease (12.61%), hypertension (33.24%), and cholelithiasis/cholecystosis (11.89%) were higher than those in the drinking-water type and tea-drinking type disease areas. The tea-drinking type disease area was dominated by individuals aged 50-60 years (38.57%), with the highest prevalence of other bone diseases (68.93%). The drinking-water type disease area had the largest proportion of patients aged 60-70 years (43.04%).Comorbidity analysis showed that the coal-burning type disease area had the highest comorbidity rate (43.98%). In terms of comorbidity patterns, the most typical combination of two concurrent diseases was diabetes-coronary heart disease, while the combination of three concurrent diseases was mainly diabetes-coronary heart disease-hypertension. The tea-drinking type disease area had a comorbidity rate of 34.29%, with the main two-disease comorbidity pattern being coronary heart disease-cholelithiasis/cholecystosis, and the three-disease comorbidity pattern adding other bone diseases to the above combination. The drinking-water type disease area had the lowest comorbidity rate (21.43%), with the main two-disease comorbidity being cholelithiasis/cholecystosis-stroke, and the three-disease comorbidity pattern being stroke combined with diabetes and hypertension.Cluster analysis independently showed that the coal-burning type disease area could be clustered into 6 categories (dominated by metabolic cardiovascular diseases), the tea-drinking type disease area into 4 categories (highlighting metabolic skeletal diseases), and the drinking-water type disease area into 5 categories (characterized by multi-system metabolic inflammatory diseases).

There are significant differences in the comorbidity patterns of skeletal fluorosis patients among coal-burning, tea-drinking, and water-drinking fluorosis endemic areas. The coal-burning endemic area is dominated by metabolic and cardiovascular diseases such as diabetes, coronary heart disease, and hypertension. In the tea-drinking endemic area, there is a significant association between coronary heart disease and gallstones/gallbladder cysts, as well as a comorbidity pattern of diabetes and pulmonary tuberculosis. The water-drinking endemic area is characterized by the association between gallstones/gallbladder cysts and stroke; meanwhile, the combination of kidney disease and metabolic diseases highlights multisystem damage.