Socioeconomic Status Is a Factor in Rising Thyroid Cancer Rates in the US

Analysis of cancer surveillance, insurance coverage, and household income data indicates that thyroid cancer rates are positively correlated with higher rates of insurance coverage and higher income.

Thyroid cancer is not only the most common endocrine cancer; it is also the fastest increasing cancer in both men and women in the US. However, it is unclear whether this the observed increase in incidence is a true increase or a reflection of improved surveillance and diagnostic techniques, according to the authors of a study presented at the 83rd Annual Meeting of the American Thyroid Association, in San Juan, Puerto Rico, on October 17, 2013.

The study authors, a team of researchers from the Department of General Surgery at NorthShore University HealthSystem, in Evanston, IL, noted that if the increase in thyroid cancer rates is in part due to increased surveillance, then incidence should vary with access to healthcare.

To test this, they analyzed cancer incidence, insurance coverage, and household income data from more than 1,200 counties in 48 US states. They obtained county-based thyroid cancer incidence from the National Cancer Institute’s State Cancer Profiles for 2009. Data on specific insurance coverage and median household income was obtained from the United States Census Bureau's Current Population Survey from 2009 to 2012.

Analysis of the data revealed that the wealthiest counties with the highest insurance coverage had the highest incidence of thyroid cancer. There was a positive correlation coefficient between cancer incidence and insurance rates (0.27, p<0.001), as well as between cancer incidence and median income (0.17, p<0.001). The authors reported that cancer incidence was more affected by insurance coverage than by median income. According to the study abstract, “each unit increase in insurance rate correlated to a 0.2 increase in thyroid cancer incidence (p<0.001).”

Six out of eight of the states with the highest thyroid cancer incidence are in a contiguous area of the Northeast of the United States, while seven out of eight of the states with the lower incidence are in a contiguous area of the Southeast. The incidence of thyroid cancer ranged from 3.9 to 39.7 throughout the 48 states whose data is reflected in the study. Data represents all races (including Hispanic), both sexes and all ages.

The authors concluded that “Thyroid cancer rates are greater in wealthier counties with higher rates of insurance coverage, suggesting that increasing thyroid cancer rates are in part due to increased surveillance. Other environmental factors also may contribute to geographic variance.”