Subclinical hyperthyroidism and dementia: the Sao Paulo Ageing & Health Study (SPAH)
1 Hospital Universitário, University of Sao Paulo, Sao Paulo, Brazil
2 School of Medicine, University of Sao Paulo, Sao Paulo, Brazil
3 Hospital das Clínicas, University of Sao Paulo, Sao Paulo, Brazil
4 Hospital João Evangelista, São Paulo, Brazil
BMC Public Health 2010, 10:298 doi:10.1186/1471-2458-10-298Published: 1 June 2010
Several epidemiologic studies have shown a possible association between thyroid function and cognitive decline. Our aim was to evaluate the association of subclinical hyperthyroidism and dementia in a population sample of older people
A cross-sectional study - São Paulo Ageing & Health Study (SPAH) - in a population sample of low-income elderly people ≥ 65 years-old to evaluate presence of subclinical thyroid disease as a risk factor for dementia. Thyroid function was assessed using thyrotropic hormone and free-thyroxine as well as routine use of thyroid hormones or antithyroid medications. Cases of dementia were assessed using a harmonized one-phase dementia diagnostic procedure by the "10/66 Dementia Research Group" including Alzheimer's disease and vascular dementia. Logistic regression models were used to test a possible association between subclinical hyperthyroidism and dementia.
Results and discussion
Prevalence of dementia and of subclinical hyperthyroidism were respectively of 4.4% and 3.0%. After age adjustment, we found an association of subclinical hyperthyroidism and any type of dementia and vascular dementia (Odds Ratio, 4.1, 95% Confidence Interval [95% CI] 1.3-13.1, and 5.3 95% CI, 1.1-26.4; respectively). Analyzing data by gender, we found an association of subclinical hyperthyroidism with dementia and Alzheimer's disease only for men (OR, 8.0; 95% CI, 1.5-43.4; OR, 12.4; 95% CI, 1.2-128.4; respectively). No women with subclinical hypothyroidism presented Alzheimer's disease in the sample.
The results suggest a consistent association among people with subclinical hyperthyroidism and dementia.