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Table 2 Mean age at onset of smoking and cigarettes per day by age*

From: Gender and age differences among current smokers in a general population survey

  Women Men   T Chi2 P Effect size
  n ever smokers mean
% current
smokers
within ever
smokers
n ever smokers mean
% current
smokers
within ever
smokers
mean difference (standard error)    
Total         
Age         
10 – 19         
   mean age at onset (SD) cigarettes per day 1303 15.2 (1.6) 1663 15.4 (1.6) 0.2 (0.1) -2.7 .01 0.10
4 or less % 430 89.1 496 91.1   1.1 ns  
5 – 20 % 854 95.4 1174 97.8   8.7 .01 .07
21 or more % 55 87.3 71 97.2   4.7 .05 .19
20 – 29         
   mean age at onset (SD) cigarettes per day 4419 16.7 (2.6) 5367 16.8 (2.5) 0.1 (0.1) -1.7 ns 0.04
4 or less % 1104 69.3 796 75.9   10.1 .01 .07
5 – 20 % 3142 81.9 4029 87.7   46.6 .001 .08
21 or more % 356 83.1 741 88.5   5.9 .05 .07
30 – 39         
   mean age at onset (SD) cigarettes per day 7493 17.3 (3.4) 8976 17.0 (3.2) 0.2 (0.1) 4.1 .001 0.06
4 or less % 1639 58.3 996 62.9   5.3 .05 .04
5 – 20 % 5365 72.2 6420 75.5   16.3 .001 .04
21 or more % 782 79.8 1831 79.2   0.1 ns  
40 – 49         
   mean age at onset (SD) cigarettes per day 6464 18.4 (4.5) 8769 17.5 (3.7) 1.0 (0.1) 13.9 .001 0.23
4 or less % 1248 51.3 836 48.8   1.2 ns  
5 – 20 % 4646 68.0 5674 65.7   6.0 .05 .02
21 or more % 802 72.6 2235 67.8   6.3 .05 .04
50 – 59         
   mean age at onset (SD) cigarettes per day 4156 21.1 (6.6) 7454 18.5 (4.8) 2.7 (0.1) 23.0 .001 0.48
4 or less % 911 42.2 729 42.5   0.2 ns  
5 – 20 % 2867 61.8 4736 52.1   69.5 .001 .10
21 or more % 543 61.9 1829 50.8   20.7 .001 .09
60 – 69         
   mean age at onset (SD) cigarettes per day 2618 24.3 (9.0) 6825 19.3 (6.1) 5.0 (0.2) 26.2 .001 0.68
4 or less % 702 36.5 803 35.0   0.4 ns  
5 – 20 % 1795 55.0 4310 38.6   138.5 .001 .15
21 or more % 225 48.0 1382 31.6   22.2 .001 .12
70 – 79         
   mean age at onset (SD) cigarettes per day 1848 25.4 (10.2) 4060 20.0 (6.6) 5.5 (0.3) 21.1 .001 0.66
4 or less % 662 23.6 601 23.3   0.0 ns  
5 – 20 % 1174 40.5 2515 22.6   123.2 .001 .18
21 or more % 107 33.6 564 15.6   17.1 .001 .17
80 or older         
   mean age at onset (SD) cigarettes per day 440 26.5 (11.5) 956 21.4 (7.5) 5.1 (0.6) 8.5 .001 0.55
4 or less % 198 24.2 174 20.1   0.9 ns  
5 – 20 % 240 32.9 540 18.0   20.4 .001 .16
21 or more % 27 51.9 114 9.6   22.0 .001 .44
  1. * Means for current smokers; % current smokers within ever smokers.
  2. T T score for t-test of means.
  3. Chi2 Likelihood chi2 test result for proportions.
  4. P Significance level: .001 ≤ .001, .01 ≤ .01, .05 ≤ .05, ns not significant.
  5. Effect size Cohen's w for proportions and d for differences between means [15].
  6. SD Standard deviation.