Table 1—

Reasons for nonparticipation among eligible case and control subjects

Case subjectsControl subjects
Total eligible7792,129
Transferred to another clinic21 (2.7)
Too ill because of concomitant disease15 (1.9)21 (0.90)
Unreliable interview3 (0.4)1 (0.04)
No permission of physician2 (0.3)
Dementia64 (8.2)7 (0.30)
Refusal55 (7.1)187 (8.80)
Missed medical records22 (2.8)
Failure to establish contact74 (9.4)129 (6.00)
No monitor available17 (2.2)1 (0.04)
Erroneous exclusions33 (4.2)
Deceased; no interview11 (1.4)2 (0.09)
Case and control subjects providing information462 (59)1,781 (84)
  • Data are n (%).