BMC Public Health 2008, 8:126 http://www.biomedcentral.com/1471-2458/8/126 Table 2: Breakdown of pSoBid study subjects Sex/Depcat Age Group Completed Visit 1 & 2 Withdrew after Visit 1 Replied 'No' Non-Respondents Sent Letters LD Female LD Female LD Female LD Female LD Male LD Male LD Male LD Male LD Participants MD Female MD Female MD Female MD Female MD Male MD Male MD Male MD Male MD Participants GRAND 35–44 45–54 55–64 Total 35–44 45–54 55–64 Total 35–44 45–54 55–64 Total 35–44 45–54 55–64 Total TOTAL 55 (30.4%) 56 (31.5%) 60 (49.2%) 171 (35.6%) 52 (21.6%) 58 (34.7%) 61 (51.2%) 171 (32.4%) 342 (33.9%) 55 (17.3%) 55 (26%) 58 (27.2%) 168 (22.6%) 49 (13.6%) 53 (16.5%) 54 (19.3%) 156 (16.2%) 324 (19.0%) 666 (24.6%) 2 (1%) 4 (2.2%) 1 (0.8%) 7 (1.4%) 2 (0.8%) 1 (0.6%) 2 (1.7%) 5 (1%) 12 (1.2%) 6 (1.9%) 5 (2.4%) 2 (1%) 13 (1.8%) 2 (0.5%) 4 (1.3%) 3 (1.1%) 9 (0.9%) 22 (1.3%) 34 (1.3%) 66 (36.5%) 74 (41.6%) 46 (37.7%) 186 (38.7%) 74 (30.7%) 51 (30.6%) 31 (26.1%) 156 (29.6%) 342 (33.9%) 70 (22.0%) 69 (32.7%) 81 (38.0%) 220 (29.6%) 56 (15.5%) 79 (24.6%) 115 (41.0%) 250 (26.0%) 470 (27.6%) 812 (29.9%) 58 (32.1%) 44 (24.7%) 15 (12.3%) 117 (24.3%) 113 (46.9%) 57 (34.1%) 25 (21.0%) 195 (37.0%) 312 (31%) 187 (58.8%) 82 (38.9%) 72 (33.8%) 341 (46.0%) 254 (70.4%) 185 (57.6%) 108 (38.6%) 547 (56.9%) 888 (52.1%) 1,200 (44.2%) 181 (100%) 178 (100%) 122 (100%) 481 (100%) 241 (100%) 167 (100%) 119 (100%) 527 (100%) 1008 (100%) 318 (100%) 211 (100%) 213 (100%) 742 (100%) 361 (100%) 321 (100%) 280 (100%) 962 (100%) 1704 (100%) 2712 (100%) LD = Least Deprived. MD = Most Deprived The total response rates were calculated by combining those who completed Visit 1 & 2 (column 3) with those who withdrew after Visit 1 (column 4). (29.9%) people declined to participate and 1,200 (44.3%) did not respond (Figure 1). Data collection was completed in April 2007 and data quality was tested over the summer of 2007. For calculation of response rate the denominator used was the total number invited to partic- ipate in the study. There were 224 people in the sample who were not con- tactable. Letters were returned by the postal services because the addressee had moved or was not known at that address (Figure 1). Males in the MD category were more often not contactable (12.4%) compared to the other subjects (6.6% LD males, 5% MD females and 2.4% LD females). GPs removed 103 subjects from the sample as they felt that the subjects were not able to complete the study (house bound, too ill to participate, terminal illness or lit- eracy problems). Eighty-three were from the MD subjects (35 females and 48 males) and 20 were from the LD sub- jects (15 females and 5 males). Response The number of letters sent in each of the 12 groups to recruit a target of 60 subjects was varied according to the group's response rate (Table 2). The highest number of let- ters (361) was sent to 35–44 year old males in the MD group (response rate = 14%); the fewest (119 and 122 respectively) were sent to 55–64 year old males and females in the LD participants (response rate 52.9% and 50% respectively – Figure 2). Although the initial target was 60 per group (720 in total), we stopped recruitment at 700 (in line with the power calculation) due to time constraints. Of the 700 subjects who participated in the study only 34 (4.9%) did not complete both visits. Of these, 12 were 35–44 years old; 14 were 45–54 years and 8 were 55–64 years (Table 2). There were 171 male and 171 female participants in the LD group and 168 females and 156 males in the MD group (Table 2). The response rate was 33.9% for LD and 19.0% for MD participants, and response rate by age group was 31.7% in 35–44 year olds, 33.3% in 45–54 year olds and 35% in 55–64 year olds. A total of 812 subjects (Table 2) in the sample declined (replied NO to the invitation). There were more females who declined (LD = 38.7% and MD = 29.6%) than males (LD = 29.6% and MD = 26.0%). In the MD group (35–44 year olds were less likely to respond than were 55–64 year olds, but this age difference was not seen in the LD subjects. A total of 1,200 people in the sample did not respond to the letter; the non-response was 52.1% for MD and 30.9% for LD subjects. More males did not respond (LD = 37% Page 7 of 11 (page number not for citation purposes)