Thyroid cancer incidence and socioeconomic indicators of health care access.
OBJECTIVE
It has been hypothesized that changes in diagnostic practices have driven the dramatic rise in thyroid cancer incidence over the past two decades. This study investigated the relation between the incidence of thyroid cancer and socioeconomic indicators of health care access.


METHODS
We examined thyroid cancer incidence trends in Wisconsin, USA, between 1980 and 2004, according to patient and tumor characteristics. Ecologic analyses were conducted by county to examine the relation between thyroid cancer incidence and education, income, and health insurance coverage.


RESULTS
The incidence of thyroid cancer nearly doubled in Wisconsin between 1980 and 2004, with almost all of the increase occurring between 1990 and 2004, during which an annual change of 4.0% (95% CI: 3.3-4.6) was observed. The bulk of the increase consisted of small, localized cancers of papillary histology. Ecologic analyses indicated moderate correlations by county between thyroid cancer incidence and median household income (r = 0.25), percent of residents with a college degree (r = 0.24), and percent of residents with health insurance (r = 0.41).


CONCLUSIONS
The association between thyroid cancer incidence and socioeconomic indicators of health care access is consistent with the hypothesis that the rising incidence trend is attributable to utilization of new diagnostic practices.
Sprague
Brian L
BL
Department of Population Health Sciences, University of Wisconsin-Madison, 610 Walnut Street, Madison, WI 53726, USA.
Warren Andersen
Shaneda
S
Trentham-Dietz
Amy
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006297:Health Services Accessibility; D006801:Humans; D015994:Incidence; D007354:Insurance, Major Medical / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D012959:Socioeconomic Factors; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D014922:Wisconsin / Q000453:epidemiology