Increasing Prevalence and Incidence of Thyroid Disease in Tayside, Scotland: The Thyroid Epidemiology Audit and Research Study (TEARS)

G. P. Leese; R. V. Flynn; R. T. Jung; T. M. MacDonald; M. J. Murphy; A. D. Morris

Disclosures

Clin Endocrinol. 2008;68(2):311-316. 

In This Article

Summary and Introduction

Summary

Objective: We aimed to describe the changing incidence of thyroid disease in a population-based study in Tayside, Scotland (population 390 000) between 1994 and 2001.
Design: A retrospective, data-linkage, population-based study measuring the incidence and prevalence of thyroid disease.
Patients: All patients with newly diagnosed, treated and stable thyroid disease in Tayside were identified by electronic linkage of six datasets, including all regional biochemistry data, hospital admissions, deaths and a thyroid follow-up register.
Results: The overall prevalence of thyroid dysfunction has increased from 2.3% to 3.8% (1994-2001). The prevalence of ever having had hyperthyroidism increased from 0.86% to 1.26% in females and 0.17% to 0.24% in males (P < 0.0001 for both). The standardized incidence of hyperthyroidism increased from 0.68 to 0.87 per 1000 females/year, representing a 6.3% annual increase (P < 0.0001). The prevalence of primary hypothyroidism increased from 3.12% to 5.14% in females and 0.51% to 0.88% in males (P < 0.0001 for both). The standardized incidence of primary hypothyroidism did not change and varied between 3.90 and 4.89 per 1000 females/year over the 8 years. Incidence of hypothyroidism in males increased from 0.65 to 1.01 per 1000 males/year (P = 0.0017). Mean age at diagnosis of primary hypothyroidism declined in females from 1994 to 2001.
Conclusions: The prevalence of primary hypothyroidism and previous hyperthyroidism has increased in Tayside, Scotland. This is partly due to an increasing incidence of disease, increased ascertainment and earlier diagnosis of disease. This will result in an increased workload for endocrinologists and general practitioners.

Introduction

Thyroid disease is a common condition with varied aetiology. In the UK, hypothyroidism is managed almost exclusively in primary care, whereas hyperthyroidism and other thyroid conditions usually require input from hospital specialists. Untreated thyroid disease is associated with morbidity,[1,2] which can be reduced by effective treatment. It is important to understand the epidemiology of thyroid disease if we are to define its impact on health-care resource use. The incidence and prevalence of thyroid disease, and especially hyperthyroidism, have been reported previously. In Europe the incidence of primary hypothyroidism varies from 0.14 to 3.53 per 1000 people/year.[3,4,5,6,7,8] The incidence is less in areas of significant iodine deficiency.[3,4,5,9,10] Prevalence of hypothyroidism varies from 1.4% in Denmark to 4.8% in Norway.[8,11,12,13] The incidence of hyperthyroidism varies from 0.26 to 0.93 per 1000 people/year in Europe,[4,5,6,7,8,14,15] but is more common in areas of iodine deficiency. Although there is clear geographical variation in the incidence of thyroid disorders, few studies have looked at the changing incidence of thyroid diseases within a single centre. Some reports indicate a decreasing incidence of hyperthyroidism[16] whereas others have shown an increasing incidence.[15] Similarly, there are fewer reports of the changing incidence of hypothyroidism in a population study. We have previously reported the prevalence of thyroid disease in Tayside, Scotland, [8] and are now able to report on the annual incidence and prevalence of different thyroid conditions over an 8-year period from 1994 to 2001.

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