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Table 2 Score of the PSQI components and PSQI total score in overall participants, nonsmokers, and cigarette smokers

From: Sleep quality in cigarette smokers and nonsmokers: findings from the general population in central China

Variables Total Nonsmokers Smokers P*
(n = 26,035) (n = 19,466) (n = 6569)
Subjective sleep quality, M ± SD 0.82 ± 0.65 0.79 ± 0.64 0.91 ± 0.66 < 0.001
Sleep latency, M ± SD 0.77 ± 0.73 0.75 ± 0.72 0.82 ± 0.75 < 0.001
 ≤15 min, % 38.6% 39.3% 36.4%
 16-30 min, % 48.2% 48.1% 48.2%
 31-60 min, % 11.0% 10.4% 12.6%
 > 60 min, % 2.3% 2.1% 2.8%
Sleep duration, M ± SD 0.58 ± 0.78 0.55 ± 0.76 0.67 ± 0.81 < 0.001
 > 7 h, % 58.1% 59.9% 52.6%
 5–7 h, % 40.4% 38.7% 45.6%
 < 5 h, % 1.5% 1.4% 1.8%
Habitual sleep efficiency*, M ± SD 0.33 ± 0.73 0.32 ± 0.71 0.35 ± 0.76 0.047
 ≥85%, % 78.6% 78.9% 77.9%
 75–84%, % 13.3% 13.3% 13.2%
 65–74%, % 4.6% 4.5% 4.7%
 < 65%, % 3.6% 3.4% 4.2%
Sleep disturbance, M ± SD 0.78 ± 0.55 0.75 ± 0.56 0.86 ± 0.52 < 0.001
Need for sleep medications, M ± SD 0.11 ± 0.38 0.11 ± 0.37 0.12 ± 0.42 0.807
 Not during the past month, % 91.4% 91.4% 91.3%
 Less than once a week, % 6.9% 7.1% 6.3%
 Once or twice a week, % 1.4% 1.3% 1.8%
 ≥3 times a week, % 0.4% 0.3% 0.6%
Daytime dysfunction, M ± SD 0.88 ± 0.84 0.84 ± 0.83 1.00 ± 0.86 < 0.001
PSQI total score, M ± SD 4.26 ± 2.67 4.11 ± 2.62 4.72 ± 2.75 < 0.001
sleep disturbances (PSQI > 5), % 26.5% 24.5% 32.7% < 0.001
  1. M mean, SD standard deviation, n number, % the percentage of subjects, PSQI Pittsburgh Sleep Quality Index
  2. Difference in percentage or mean differences analyzed between nonsmokers and smokers by the Chi-squared test and the Wilcoxon rank sum test (Mann-Whitney U-test) respectively
  3. * Significant difference between groups of nonsmokers and smokers, p < 0.01
  4. The score range is 0–70, with higher scores indicating poorer functioning
  5. Habitual sleep efficiency* = total hours of sleep/(get-up time − bedtime) × 100%