Thyroid dysfunction and its associated factors: a cross-sectional study based on Rafsanjan cohort study in the...

This study aimed to determine the prevalence and associated factors with thyroid dysfunction within a large cohort participating in the Rafsanjan Cohort Study (RCS), part of the Prospective Epidemiological Research Studies in Iran (PERSIAN).

A cross-sectional study based on RCS.

The study was carried out in Rafsanjan, a region in the southeast of Iran.

Participants were chosen using a cluster sampling technique. A total of 9991 participants between the ages of 35 and 70 years from both genders participated in the initial phase of the RCS.

Thyroid dysfunction was determined based on self-reported diagnosis.

The association of thyroid dysfunction with gender, age, body mass index (BMI), physical activity, substance use, education and Wealth Score Index (WSI) was assessed using multivariable logistic regression.

Among 9867 participants, thyroid dysfunction prevalence was 8.98%. Women had 6.56 times higher odds compared with men (OR: 6.56, 95%CI 5.03 to 8.55). BMI ≥30 had 22% higher odds compared with BMI <25 (OR: 1.22, 95% CI 1.01 to 1.50). Middle high WSI and high WSI were positively associated with thyroid dysfunction (OR: 1.35, 95% CI 1.11 to 1.65 and OR: 1.61, 95% CI 1.17 to 2.23, respectively). Former smoking was associated with increased odds of thyroid dysfunction (OR: 1.65, 95% CI 1.14 to 2.38). Age groups 46-55 years and ≥56 years exhibited higher odds of hypothyroidism compared with 35-45 years (OR: 1.47, 95% CI 1.15 to 1.87 and OR: 1.61, 95% CI 1.24 to 2.09, respectively).

This study shows the elevated burden of thyroid dysfunction among women and older adults and highlights modifiable associated factors such as BMI and smoking history. These findings emphasise the need for targeted screening and lifestyle interventions in high-risk groups. Future longitudinal studies are warranted to elucidate causal pathways.