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Table 3 Effect of smoking on menopause among postmenopausal women (KNHANES, 2007–2014)

From: Factors associated with menstrual cycle irregularity and menopause

Variables Early menopause (< 50 years) Late menopause (≥50 years) Logistic regression for early menopause (< 50 years)a Linear regression for menopausal age (categorical variable)a Linear regression for menopausal age (continuous variable)a
n % n % OR 95% CI β SE p-value β SE p-value
(mean) (SD) (mean) (SD)
Total 4930 45.9 5767 54.1          
Current age, mean (SD) 64.5 0.2 62.8 0.2          
Average menopausal age, mean (SD) 45.6 0.1 52.5 0.0          
Smoking status
 Non-smoker 4447 90.6 5343 93.6 1.00    1.000      
 Ex-smoker 172 3.7 160 2.9 1.34 1.02 1.77 −0.615 0.365 0.093    
 Current smoker 236 5.7 175 3.5 1.68 1.30 2.17 −1.137 0.283 <.0001    
 Total 4855 100.0 5678 100.0          
Cigarettes per day
 Non-smoker 4447 92.3 5343 95.1 1.00    1.000      
 < 20 cigarettes 268 6.1 205 3.9 1.61 1.26 2.07 −1.104 0.302 0.000    
 ≥ 20 cigarettes 69 1.5 55 1.0 1.53 1.00 2.33 −0.486 0.444 0.274    
 Total 4784 100.0 5603 100.0        −0.038 0.019 0.046
Age at smoking initiationb
 Non-smoker 3409 89.9 3993 93.1 1.00    1.000      
 < 20 years 36 1.2 15 0.4 2.93 1.45 5.90 −1.438 0.461 0.002    
 ≥ 20 years 298 8.9 246 6.4 1.43 1.13 1.82 −0.827 0.293 0.005    
 Total 3743 100.0 4254 100.0        −0.004 0.001 <.0001
Pack-year (total)b
 Non-smoker 3409 90.2 3993 93.4 1.00         
 Below or equal to the median (≤9.8 pack-years) 153 4.9 175 3.4 1.50 1.11 2.01 −0.773 0.342 0.024    
 Above the median (>9.8 pack-years) 172 4.9 78 3.3 1.57 1.17 2.09 −1.037 0.389 0.008    
 Total 3734 100.0 4246 100.0        −0.025 0.015 0.103
Pack-year (before menopause)b
 Non-smoker 3409 92.0 3993 93.7 1.00    1.000      
 Below or equal to the median (≤5 pack-years) 133 4.0 107 2.7 1.54 1.11 2.13 −1.076 0.370 0.004    
 Above the median (>5 pack-years) 123 4.0 131 3.6 1.14 0.83 1.57 0.417 0.340 0.220    
 Total 3665 100.0 4231 100.0        0.035 0.020 0.077
  1. OR odds ratios, CI confidence interval; a Univariate model  b Excluded KNHANES 2013-2014 because age at smoking initiation was not surveyed