Sociodemographic factors influencing participation in the Barcelona Health Survey study on serum concentrations of persistent organic pollutants

Background: Little is known about factors affecting participation in population-based biomonitoring studies. We analyzed socioeconomic factors influencing participation in the Barcelona Health Survey (BHS) study on the distribution of serum concentrations of persistent organic pollutants (POPs). Methods: After completing the BHS personal interview at home participants aged ≥15 years were invited to donate blood. Conducted on a different date and location, the POPs study included additional questions, blood extraction, and a brief physical examination. Factors influencing participation were analyzed by logistic regression. Results: Of 523 BHS participants that we contacted to participate in the study, 231 (44%) participated; they were broadly representative of the city population regarding sex, birth place, body mass index (BMI), employment status and occupational social class. Participants in the POPs study had higher educational level and family income. Controlling for confounders, participation was slightly higher among women than men (odds ratio [OR] = 1.38, p = 0.02), and lower among the youngest and oldest subjects (p = 0.002), with a strong and monotonic trend of increasing participation with increasing educational level (p < 0.001) (OR for university level vs. no studies = 4.58, 95% CI: 2.3-9.3). Conclusions: Although participation was somewhat low, participants were similar to the city population regarding sex, BMI, birth place, employment, and occupational social class. Health surveys that integrate environmental biomarkers should invest specific resources to encourage participation of the youngest and oldest individuals, and of those with more disadvantaged socioeconomic position (particularly, citizens with lowest education). © 2009 Elsevier Ltd. All rights reserved.