Supplementary Material for: Association Between Thyroid-Stimulating Hormone and Tooth Loss Risk in Community-Dwelling Older Adults in Taipei City: A Prospective Cohort Study

Background: This study assessed the association between thyroid-stimulating hormone (TSH) levels and the risk of tooth loss.
Methods: From 2005 to 2013, 56,743 community-dwelling individuals aged ≥65 years underwent biennial physical examinations in Taipei. Dental evaluations documented tooth count and TSH levels were measured using a third-generation assay. Participants averaged 3.4 follow-ups over 4.9 years and were categorized into four groups based on plasma TSH concentrations. A generalized estimating equation model analyzed the longitudinal relationship between tooth loss and TSH levels
Results: Participants’ mean age was 73.1 years (SD, 6.3), being highest in the clinical hypothyroidism group (74.6 years) and lowest in the euthyroid group (73.0 years). Hypertension and diabetes were more prevalent in the clinical hypothyroidism group. Periodontitis rates were consistent across TSH categories, and 81.5% of participants retained ≥20 teeth, 12.0% had 10–19 teeth, and 6.5% had 1–9 teeth. Severe tooth loss (1–9 teeth) was slightly more frequent in the clinical hypothyroidism group (6.7%), suggesting a potential link between thyroid function and tooth retention. Multivariable-adjusted models found no significant association between subclinical hypothyroidism and tooth loss, whereas clinical hypothyroidism reduced risk (OR = 0.82, 95% CI: 0.74–0.92). Stratified analysis showed this protective effect in those with ≥20 teeth and in individuals aged 65–75 years (OR = 0.79). Conversely, subclinical hypothyroidism increased tooth loss risk in participants aged ≥75 years (OR = 1.12). Sex-stratified analysis revealed 26% lower risk in females with clinical hypothyroidism (OR = 0.74), suggesting age- and sex-specific influences of thyroid function on oral health.
Conclusion: This study suggests a link between clinical hypothyroidism and reduced tooth loss, particularly in women and individuals aged 65–75 years. Conversely, subclinical hypothyroidism in persons ≥75 years correlates with greater risk, underscoring the role of thyroid function in geriatric oral health.