Another subanalysis was done, restricted to study participants who changed home address at least once during followup. selleck inhibitor In order to investigate whether concentration differences between study inclusion and average over followup were differential with respect to common diseases, risk factors, and socioeconomy, we stratified data on the following variables: sex, age, body mass index categories, education level, hypertension, diabetes, cardiac disease, self-estimated health, smoking (all at study inclusion), and cancer during followup.3. ResultsThe average length of followup was 14.6 years, and the average study participant had changed home address 1.75 times (Table 1). The average NOx concentration from inclusion to followup seemed to be in good accordance with the concentrations at inclusion, with a correlation coefficient of 0.

80 and with the scatterplot and histogram revealing generally small absolute differences between the two measures (Table 2 and Figures Figures22 and and3).3). Restricting the analysis to those who had changed home address at least once only marginally lowered the correlation (�� = 0.76; Table 2). Moreover, the weighted kappa of 0.76 reveals substantial agreement for the categorized variables (Table 3). Other choices of categorization yielded similar kappa-values (data not shown). Not only were the absolute differences in concentration low, the relative differences were also rather small; more than 85% of the cohort had an average concentration over followup that differed less than 25% from the concentration at baseline.

The NOx concentrations over followup thus differed from the NOx concentrations at baseline with more than 25% for 15% of the cohort, but over- and underestimation of the concentrations seemed equally frequent (Figures (Figures22 and and3).3). The GSK-3 large number of study participants (approximately 16000) for whom the concentration at inclusion is identical to the average concentration during followup is explained by the fact that no temporal adjustment (back-extrapolation) of the concentrations has been undertaken. Thus, if a study participant had not changed home address during followup, the study inclusion concentration is per se equal to the average concentration.Figure 2Scatterplot of the NOx concentrations at inclusion versus follow-up average concentrations (Pearson correlation coefficient = 0.80).Figure 3Histogram of NOx concentration differences between inclusion and follow-up average concentrations. The highest bar represents those with a 0 or very small difference (n = 15, 962) and has been truncated. Table 1Descriptive data of the cohort (25,725 observations).