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Table 2 Rate ratios (RR) and 95% confidence intervals (CI) of amyotrophic lateral sclerosis (ALS) by smoking status before the onset of ALS, General Practice Research Database (GPRD), 1990-2008

From: Association of smoking with amyotrophic lateral sclerosis risk and survival in men and women: a prospective study

  ALS cases Controls RR (95% CI) * RR (95% CI)**
Entire sample
Never 377 (33.0) 3714 (32.7) 1.00 (ref.) 1.00 (ref.)
Ever 575 (50.3) 5615 (49.4) 1.04 (0.80-1.34) 1.09 (0.81-1.46)
   Former 273 (23.9) 2696 (23.7) 1.01 (0.74-1.39) 1.15 (0.80-1.64)
   Current 302 (26.4) 2919 (25.7) 1.06 (0.79-1.41) 1.04 (0.74-1.47)
Missing 191 (16.7) 2042 (18.0) 0.88 (0.68-1.14) 0.94 (0.69-1.26)
Men
Never 207 (32.8) 1896 (30.3) 1.00 (ref.) 1.00 (ref.)
Ever 318 (50.4) 3180 (50.8) 0.75 (0.53-1.06) 0.75 (0.50-1.11)
   Former 157 (24.9) 1584 (25.3) 0.73 (0.48-1.11) 0.70 (0.43-1.14)
   Current 161 (25.5) 1596 (25.5) 0.76 (0.52-1.13) 0.79 (0.50-1.24)
Missing 106 (16.8) 1191 (19.0) 0.64 (0.44-0.92) 0.67 (0.44-1.02)
Women
Never 170 (33.2) 1818 (35.6) 1.00 (ref.) 1.00 (ref.)
Ever 257 (50.2) 2435 (47.7) 1.53 (1.04-2.23) 1.68 (1.08-2.61)
   Former 116 (22.7) 1112 (21.8) 1.49 (0.92-2.43) 2.06 (1.20-3.53)
   Current 141 (27.5) 1323 (25.9) 1.55 (1.01-2.38) 1.41 (0.84-2.36)
Missing 85 (16.6) 851 (16.7) 1.25 (0.85-1.82) 1.33 (0.86-2.04)
P interaction    0.01 0.02
  1. * Conditional logistic regression model adjusted for age, gender, practice, and time since enrolment in the GPRD.
  2. ** Results advancing five years index date (910 cases and 9058 controls). Conditional logistic regression model adjusted for age, gender, practice, and time since enrolment in the GPRD.