Table 1. Distributions of the study population in each arm of the trial by sex, age, screening episode type, hub and IMD quintile.

	Usual reminder		Enhanced reminder		Total
Factor	No.	%	No.	%	No.	%
Sex
Male	46 839	51.8	40 320	51.7	87 159	51.7
Female	43 574	48.2	37 747	48.4	81 321	48.3
Age (years)a
<65	46 771	51.7	38 390	49.2	85 161	50.6
65–69	27.781	30.7	24 870	31.9	52 651	31.2
70–74	15 861	17.5	14 807	19.0	30 668	18.2
Screening episode type
Prevalent first time	21 271	23.5	14 483	18.5	35 754	21.2
Incident	25 813	28.5	23 722	30.4	49 535	29.4
Prevalent previous non responder	43 329	47.9	39 862	51.1	83 191	49.4
Hub
Midlands and NorthWest	25 490	28.2	22 051	28.2	47 541	28.2
Southern	23 107	25.6	19 131	24.5	42 238	24.5
London	10 385	11.5	10 809	13.8	21 194	13.8
North East	12 796	14.1	12 291	15.7	25 087	15.7
Eastern	18 635	20.6	13 785	17.7	32 420	17.7
IMD quintileb
1 (least deprived)	18 928	20.9	15 933	20.4	34 861	20.7
2	19 446	21.5	16 594	21.3	36 040	21.4
3	18 286	20.2	16 092	20.6	34 378	20.4
4	16 853	18.6	14 679	18.8	31 532	18.7
5 (most deprived)	16 489	18.2	14 441	18.5	30 930	18.4
Not known	411	0.4	328	0.4	739	0.4
Total	90 413		78 067		168 480

‘Prevalent first time': people being invited for the first time.

‘Incident': invitations to people who have participated in screening previously.

‘Prevalent previous non responder': people invited to be screened at least once previously, who have never responded.

^aSome individuals were invited just before their 60th birthday

^bIndex of multiple Deprivation: quintile based on national distributions using pre-defined national cut-offs.