Table 1

 Comparisons of respondents and non-respondents in the 1994 and 2001 cohorts (mean (95% CI for continuous variables, percentage for counts)

19942001
Respondents (n = 932)Non-respondents (n = 384)p ValueRespondents (n = 830)Non-respondents (n = 583)p Value
*Two sample t test; †χ2 test.
Age (years)60.6 (59.7 to 61.5)62.4 (61.0 to 63.8)0.03*60.8 (59.9 to 61.7)58.0 (56.7 to 59.2)0.001*
Women (%)78.881.50.02†78.376.20.38†
Disease duration (years)12.6 (12.0 to 13.3)14.2 (13.0 to 15.4)0.26*13.9 (13.2 to 14.6)14.4 (13.6,15.3)0.34*