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Table 3 Risk factors stratified by time after intended end of isoniazid preventive therapy (intention-to-treat)

From: The timing of tuberculosis after isoniazid preventive therapy among gold miners in South Africa: a prospective cohort study

   Year 0–1 Year 1+  
Total   pyrs TB aHR (95 % CI) a pyrs TB aHR (95 % CI) a P value b
Sex Male 15,759 344 1 7,277 179 1 0.15
  Female 709 15 0.82 (0.49–1.38) 290 3 0.35 (0.11–1.11)  
Age, years ≤29 2,229 18 1 992 12 1 0.54
  30–39 4,465 81 2.27 (1.36–3.79) 2,196 50 1.90 (1.01–3.56)  
  40–49 6,995 189 3.27 (2.01–5.30) 3,295 87 2.14 (1.17–3.91)  
  ≥50 2,779 71 3.01 (1.79–5.06) 1,085 33 2.42 (1.25–4.70)  
Years in workforce 0–9 4,436 58 1 1,956 27 1 0.15
  10–19 4,543 84 1.48 (1.06–2.08) 2,314 63 2.05 (1.30–3.22)  
  20–29 5,213 155 2.23 (1.65–3.02) 2,395 62 1.86 (1.18–2.92)  
  ≥30 2,229 61 2.03 (1.41–2.91) 878 29 2.35 (1.39–3.97)  
Type of work Surface 1,465 20 1 700 10 1 0.98
  Underground 14,932 339 1.71 (1.09–2.69) 6,830 169 1.72 (0.91–3.27)  
Type of housing Hostel 9,681 236 1 4,697 128 1 0.57
  Other 6,787 123 0.69 (0.55–0.86) 2,870 54 0.62 (0.45–0.85)  
Previous TB No 14,618 281 1 6,795 149 1 0.63
  Yes 1,838 78 2.15 (1.68–2.77) 767 33 1.93 (1.32–2.81)  
Self-reported ART use No 16,013 346 1 7,373 177 1 0.82
  Yes 439 12 1.28 (0.72–2.27) 186 5 1.13 (0.46–2.75)  
Number of IPT prescriptions 1–2 4,321 99 1 2,192 60 1 0.86
  3–5 1,715 36 0.88 (0.60–1.29) 842 20 0.84 (0.50–1.39)  
  6+ 10,433 224 0.82 (0.65–1.05) 4,534 102 0.79 (0.42–1.46)  
  1. a Adjusted for cluster. b Test for interaction for factor with time
  2. aHR, Adjusted hazard ratio; ART, Antiretroviral therapy; CI, Confidence interval; HR, Hazard ratio; IPT, Isoniazid preventive therapy; pyrs, Person-years; TB, Tuberculosis