Table 1 Characteristics of included studies reporting on the association between smoking and surgery in Crohn’s disease
Study | Country | Source of patients | Definition of smoking | Timing of smoking | Duration of follow-up | Sample size | Adjusted estimates |
|---|---|---|---|---|---|---|---|
Deepak 2015 [12] | Unknown | Unknown | Not provided | Unknown | Unknown | 79 | Age at diagnosis; sex; disease duration; response to treatment |
Frolkis 2016 [14] | UK | Population-based | Patient coded in EMR as Current, Former, or Never Smoker within one year of index (diagnosis date) | At diagnosis | Median (Q1, Q3): 5 years (3, 7) | 1519 | Sex; use of immunosuppressants; steroid use within 90 days of diagnosisa |
Kariyawasam 2014 [6] | Australia | Tertiary care | Not provided | At diagnosis | Median (Q1, Q3): 11 years (5, 19) | 1035 | Crude |
Lawrance 2013 [7] | Australia; New Zealand | Tertiary care | Current: ≥1 cigarette/day for ≥3 months Former: Smoker who ceased smoking for ≥3 months and had not recommenced prior to the end of follow-up Never: Never regularly smoked ≥1 cigarette/day or had not smoked | At diagnosis | Mean (sd): 17 (9) years | 1115 | Disease location; perianal disease |
Moon 2014 [8] | Korea | Tertiary care | Not provided | At diagnosis | Mean (range): 4 years (0.5, 18) | 728 | Age at diagnosis; sex; family history of IBD; disease location; disease behaviour; perianal disease |
Ng 2016 [13] | Asia (8 countries) and Australia | Population-based | Not provided | At diagnosis | Median (Q1, Q3): 18 months (12, 23) | 413 | Age; sex; disease behaviour; disease location; perianal disease; treatment within first 3 months; region (Australia vs. Asia) |
Peyrin-Biroulet 2012 [9] | USA | Population-based | Not provided | At diagnosis | Median: 12 years | 310 | Sex; disease location; disease behaviour; need for steroids within 90 days of diagnosis |
Renda 2008 [10] | Italy | Tertiary care | Current: ≥7 cigarettes/week for >12 months before diagnosis Former: Smoker who quit ≥1 year before diagnosed and had smoked ≥1 year | At diagnosis | Mean: 6 years | 182 | Crude |
Solberg 2007 [11] | Norway | Population-basedb | Current: >7 cigarettes/week Former: Years of starting and stopping smoking were compared with years of diagnosis and surgery | At diagnosis | All patients followed for 10 years | 237 | Crude |