Table 1.

Development of the study sample

	Sample addressed T0(2001) n (%)	Non-participants n (%)	Study sample T1(2001) n (%)	Drop-outs T1 – T2 n (%)	Study sample T2(2003) n (%)	Drop-outs T1 – T3 n (%)	Study sample T3(2005) n (%)
Gender
female	487 (49)	108 (37)	379 (53)	96 (50)	283 (54)	98 (51)	281 (54)
male	517 (51)	181 (63)	336 (47)	97 (50)	239 (46)	95 (49)	241 (46)
Age in years
mean			27.4	27.6	29.3	31.5	31.3
range			23 – 44	23 – 44	26 – 44	29 – 48	27 – 46
Total	1004	289	715	193	522	193	522
Study sample			715 (100%) (71% of 1004)		522 (73% of 715) (52% of 1004)		522 (73% of 715) (52% of 1004)