Five-year incidence and progression of thyroid dysfunction in an older population
Very few studies have assessed both the incidence and progression of thyroid dysfunction in a single older population-based cohort. In this study, we aimed to assess the 5-year incidence, progression and risk factors for development of thyroid dysfunction in an older Australian population. Methods:
The Blue Mountains Eye Study is a longitudinal population-based cohort study. During 1997–1999, 1768 participants (≥55 years) had thyroid function assessed. After excluding participants reporting any form of treatment for their thyroid condition at baseline, 951 participants (91.4%) without thyroid dysfunction and 54 (5.4%) with thyroid dysfunction were re-examined 5 years later. Thyroid dysfunction was defined using serum thyrotropin (thyroid stimulating hormone (TSH)) screen, followed by serum free T4 assessment. Results:
The overall 5-year incidence of thyroid dysfunction was 4.7% (95% confidence interval (CI) 3.4–6.1). Obesity (body mass index ≥ 30 kg/m2) and serum TSH > 2 mIU/L at baseline predicted incident overt hypothyroidism (odds ratio (OR) 4.05, CI 1.74–9.41) and (OR 5.46, CI 1.16–25.67) respectively. The 5-year incidence of subclinical hypothyroidism was significantly higher in women than in men, 2.5% versus 0.7% (P= 0.03). Progression to overt hypothyroidism was observed in 17.9% of subjects with subclinical hypothyroidism over 5 years. Conclusions:
The 5-year incidence of thyroid dysfunction in this older population was relatively low, and was associated with obesity and serum TSH level > 2 mIU/L at baseline. Over one in six persons with subclinical hypothyroidism progressed to overt thyroid dysfunction over the 5-year period. Our findings highlight the need for appropriate management of subclinical hypothyroidism among older people.
Document Type: Research Article
Affiliations: 1: Centre for Vision Research, Department of Ophthalmology, Westmead Millennium Institute, 2: Department of Medicine, Nepean Clinical School, 3: International Council for Control of Iodine Deficiency Disorders, University of Sydney, Sydney, New South Wales and 4: Australian Health Policy Institute, University of Sydney,
Publication date: September 1, 2010