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Purpose: The aim of the study is to evaluate the agreement between contemporaneously recorded and subsequently recalled time spent outdoors during 1 week among members of an occupational cohort., Methods: One hundred twenty-five radiologic technologists from northern and southern geographic areas in the United States recorded time spent outdoors for 7 consecutive days in a daily diary. Six months later, study participants completed a mailed self-administered questionnaire of the number of outdoor hours during the same 7-day period. We tested the agreement between questionnaire responses and diary entries. Logistic regression models were used to identify variables significantly affecting agreement., Results: Time spent outdoors comprised one fifth of the total time recorded in the diaries. Agreement (weighted kappa [kappa(w)]) between reported outdoor time during weekdays (kappa(w) = 0.49; 95% confidence interval [CI], 0.39-0.59) was significantly (p < 0.05) higher than for weekends (kappa(w) = 0.23; 95% CI, 0.12-0.34). Similarly, agreement was lower for weekends compared with weekdays in multivariate analyses, reaching statistical significance (p = 0.05) in only the southern regions., Conclusions: Although our investigation was carried out among volunteers from the US radiologic technologist cohort, we believe retrospective questionnaires may be more accurate in reporting time spent outdoors for weekdays compared with weekends in any group of indoor workers. These differences have implications for the wording in future questionnaires about time spent outdoors and level and sources of uncertainty characterizing estimated time spent outdoors on weekdays versus weekend days.

Purpose: Little research has examined the validity of using census data to determine an individual's socio-economic status (SES), as measured by race and educational level. This study assessed the accuracy of using aggregate level data from United States Census Block Groups in determining race and education SES indicators in a cohort of women from North Carolina., Methods: The study analyzed patient data from the Carolina Mammography Registry and 1990 United States Census in 21 North Carolina counties. Women (n = 39,546) were geocoded to their census block group and their block group characteristics (surrogate measures) were validated with their self-reported values on race and education. An analysis was performed to explore whether using these surrogate measures would affect measured associations with the self-reported values., Results: Whites were accurately identified (84.8%) more consistently than Blacks (14.1%) regardless of their urban/rural status. Women without a high school diploma or equivalent were accurately identified (56.2%) more often than those with higher education levels (45.9%). Analyses using the surrogate measures were significantly different than the true values according to chi-square statistics., Conclusions: Use of census data to derive SES indicators tends to be more accurate for the majority than the minority population. Researchers must be sensitive to the ecologic fallacy when using aggregate level data such as the census to determine individual level characteristics.