Table 2.

Average sleep duration in various age-periods across the adult lifecourse and risk of lung cancer mortality in Xuanwei, China (1994–2011)

95% CI95% CI95% CI95% CI
Age periodCasesPylnHRLowerUpperPCasesPylnHRLowerUpperP
21–30 years21–30 years
≤7 hours/day6068,4231,0231.030.781.350.85607 hours/day4972,4211,0781.060.781.450.7095
8 hours/day9681,054,28315,744Ref8 hours/day7601,014,38915,130Ref
9 hours/day188201,6933,0101.070.911.260.40169 hours/day117192,0522,8380.860.701.050.1380
≥10 hours/day121130,9491,9231.190.981.450.0836≥10 hours/day91115,0691,6751.311.031.660.0262a
P-trend (ordinal)0.2071P-trend (ordinal)0.9760
31–40 years31–40 years
≤7 hours/day109140,1722,0971.120.911.390.27177 hours/day83139,2782,0801.060.831.350.6304
8 hours/day10041,086,84616,214Ref8 hours/day7731,049,74315,612Ref
9 hours/day137145,4892,1491.251.041.490.0170a9 hours/day81128,5491,9001.170.931.490.1798
≥10 hours/day8781,3251,1871.210.971.520.0989≥10 hours/day8075,2901,0921.721.342.22<0.0001b
P-trend (ordinal)0.0122aP-trend (ordinal)0.0222a
41-50 years41-50 years
≤7 hours/day211229,1433,3991.391.191.63<0.0001b7 hours/day151230,9903,4281.180.981.420.0774
8 hours/day9241,012,68214,977Ref8 hours/day713971,74214,364Ref
9 hours/day127154,3892,2761.060.881.280.52189 hours/day98141,7422,0791.261.011.560.0396a
≥10 hours/day7544,5376562.441.913.12<0.0001b≥10 hours/day5137,9325482.451.763.41<0.0001b
P-trend (ordinal)<0.0001bP-trend (ordinal)0.0013b
51–60 years51–60 years
≤7 hours/day197215,6233,0001.461.231.73<0.0001b7 hours/day150207,3992,8491.291.061.570.0130a
8 hours/day509564,0247,813Ref8 hours/day378515,5647,123Ref
9 hours/day7491,9621,2631.291.001.650.04669 hours/day4078,3701,0661.210.871.690.2607
≥10 hours/day6136,2585132.511.913.30<0.0001b≥10 hours/day5035,2904892.401.733.33<0.0001b
P-trend (ordinal)<0.0001bP-trend (ordinal)0.0009b
61-70 years61-70 years
≤7 hours/day109148,9251,9691.581.232.030.0004b7 hours/day90145,6491,9021.401.061.850.0188a
8 hours/day166238,7593,132Ref8 hours/day136220,1942,870Ref
9 hours/day4951,3996712.121.522.95<0.0001b9 hours/day1443,4185630.930.531.650.8140
≥10 hours/day4130,9714123.272.314.62<0.0001b≥10 hours/day2028,0763631.590.962.640.0704
P-trend (ordinal)<0.0001bP-trend (ordinal)0.0194a
≥71 years≥71 years
≤7 hours/day1644,5175551.620.813.260.17627 hours/day2544,2325382.471.135.380.0233a
8 hours/day2048,244595Ref8 hours/day1241,616510Ref
9 hours/day813,3131642.140.895.140.08869 hours/day39,5261161.770.466.810.4069
≥10 hours/day811,2511382.551.076.080.0343a≥10 hours/day39,1061111.160.294.640.8382
P-trend (ordinal)0.0751P-trend (ordinal)0.0255a
  • Abbreviations: Person-years lived (attained age; pyl), lung cancer–related mortality (cases).

  • aP values and P trends <0.05 were considered statistically noteworthy.

  • bP values and P trends below a Bonferroni-corrected α-level of 0.0028 (0.05/18 tests from 6 age periods × 3 parameters of sleep duration) were considered statistically significant. Separate Cox models were fitted for each age period. Separate analyses were performed for men and women. In men, Cox models were adjusted for: average hours spent performing indoor activities in the same age period as sleep (continuous counts), type of respondent (self, surrogate), other work besides farming (yes, no), educational attainment (illiterate, primary school, middle/vocational school or higher), duration of smoking (years), ever active smoking (yes, no), ethnicity (Han Chinese, other), average number of rooms and people in residences from 1976 to 1992 (continuous), fuel type used in first residence (smoky coal, smokeless coal, coal cakes, other), installation of a chimney for ventilation (stove improvement; yes, no), family history of any cancer (yes, no), average tons of fuel/coal used from 1976 to 1992 (continuous), ever employed as a miner (yes, no), age in 1976 (years), and an indicator variable for history of respiratory comorbidities (asthma, emphysema, chronic bronchitis, and chronic obstructive pulmonary disorder). In women, duration of smoking, ever smoking, and ever employed as a miner were removed due to lack of variability, while age at which one began cooking (years) was included. Prevalent (1976–1991) and incident lung cancer mortality cases in the first two years of follow-up (1992–1993) were censored, only events from 1994 to 2011 were counted. Sample sizes (n) represent those with sleep data in each age period.