AIMS AND SUBJECTS: We investigated the prospective relationship between thyroid status and the risk of dementia and Alzheimer's disease among a random sample of 1843 participants, aged 55 years and over, from the population-based prospective Rotterdam Study. METHODS: Thyroid status was measured at baseline (1990-93), through assessment of serum antibodies to thyroid peroxidase (TPO-Abs, positive: >10 IU/ml), serum TSH levels, and when TSH was abnormal (<0.4 or >4.0 mU/I), serum thyroxin levels (T4). At baseline and at follow up, after on average 2 years, participants were screened for dementia. Diagnoses were based on international criteria. RESULTS: Persons with reduced TSH levels at baseline had a more than threefold increased risk of dementia (RR = 3.5, 95%Cl: 1.2-10.0) and of Alzheimer's disease (RR = 3.5, 95%Cl: 1.1-11.5), after adjustment for age and sex. Among persons with reduced TSH levels, T4 levels appeared to be positively related to the risk of dementia (RR per SD increase = 2.9, 95%Cl: 0.7-12.2), although none of those who became demented had a T4 level above the normal range (>140 nmol/l). The risk of dementia was especially increased in subjects with low TSH who were positive for TPO-Abs (RR = 23.7, 95%Cl: 4.0-140). CONCLUSIONS: This is the first prospective study to suggest that subclinical hyperthyroidism in the elderly increases the risk of dementia and Alzheimer's disease.,
Clinical Endocrinology
Department of Immunology

Kalmijn, S., Mehta, K., Pols, H., Hofman, A., Drexhage, H., & Breteler, M. (2000). Subclinical hyperthyroidism and the risk of dementia. The Rotterdam study. Clinical Endocrinology, 53(6), 733–737. doi:10.1046/j.1365-2265.2000.01146.x