Socio-economic status and head and neck cancer incidence in Canada: a case-control study.

In an earlier study we identified an increased incidence of head and neck cancer (HNC) in individuals with lower socio-economic status (SES) in the United States. The objective of this study was to determine if lower SES is associated with a similar increase in the incidence of HNC in Canadian patients. We obtained data on SES (income, education and immigration status), demographic characteristics, frequency of dental visits and smoking behavior for adult patients residing in the Eastern Ontario region who were referred to the Ottawa Regional Cancer Centre with HNC. We compared the SES and frequency of dental visits of these HNC patients with the SES and frequency of dental visits of a control sample in the same region from the 2004-2005 Statistics Canada Canadian Community Health Survey (CCHS 3.1). We then performed a logistic regression analysis on the combined sample of patients and controls using incidence of HNC as the dependent variable. This allowed us to eliminate confounding variables such as tobacco intake and to isolate the effect of SES, frequency of dental visits, and immigration status on HNC incidence. There was a statistically significant decrease in the incidence of HNC among adults with a higher median family income (OR=0.5429, CI=[.3352, .8795]). Also, adults with less than grade 8 education had significantly higher rates of HNC than adults who had completed high school (OR 3.65, CI=[1.88, 7.08]). As well, immigrants had a significantly lower incidence of HNC than Canadian born adults (OR=0.3825, CI=[.2063, .7090]). Lastly, we found that individuals who typically visited a dentist less than once per year had a significantly higher incidence of HNC than individuals who typically visited a dentist at least once per year (OR=1.69, CI=[1.01, 2.83]). Even when controlling for tobacco intake, the incidence of HNC in Eastern Ontario was higher in patients with lower median family income and less than grade 8 education. It was higher in individuals who visited a dentist less than once per year, and lower in immigrants to Canada. This was similar to what has been observed in the United States. Further study into the reason for this increased incidence of HNC in patients with lower SES is warranted.