Dyslipidemia Is Associated With Increased Risk of Achilles Tendon Disorders in Underweight Individuals to a Greater Extent Than Obese Individuals: A Nationwide, Population-Based, Longitudinal Cohort Study

Background: The association between dyslipidemia and Achilles tendinopathy (AT) or Achilles tendon rupture (ATR) remains controversial, although some studies have examined this topic. Purpose: To evaluate the correlation of dyslipidemia and the risk of AT or ATR, and its association with body mass index (BMI), by assessing data from a nationwide population-based cohort. Study Design: Cohort study; Level of evidence, 3. Methods: We used the National Health Insurance database, which includes the entire population of the Republic of Korea, to evaluate participants in the National Health Screening Program between January 2009 and December 2010. Participants diagnosed with AT or ATR before December 31, 2017, were selected. The variables assessed were age, sex, frequency of high-intensity exercise per week, BMI, waist circumference, systolic blood pressure, and levels of low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and fasting blood glucose. Multivariate Cox proportional hazards regression was used for data analysis. Results: A total of 16,830,532 participants were included. Of these, 125,814 and 31,424 participants developed AT and ATR, respectively. A higher level of LDL-C was associated with an increased risk of AT (adjusted hazard ratio [HR], 1.16) and ATR (adjusted HR, 1.18). A slightly increased risk of AT was observed in participants with higher TG levels (adjusted HR, 1.03), whereas higher HDL-C level was associated with a slight risk reduction for AT (adjusted HR, 0.95). However, no significant association was observed between higher TG or HDL-C levels and ATR. In the underweight group (BMI <18.5 kg/m²), a higher LDL-C level was associated with an increased risk of AT and ATR by 37% and 116%, respectively, compared with lower LDL-C. Higher LDL-C level was associated with an increased risk of AT and ATR by 10% and 16%, respectively, in the obese group (BMI ≥25 kg/m²). Conclusion: Dyslipidemia was related to the development of AT and ATR. The association of higher LDL-C levels with AT and ATR risk was more pronounced in underweight than in overweight and obese individuals.