Association between nighttime sleep duration, sleep timing and falls among middle-aged and older Chinese population: A cross-sectional analysis from the Dongfeng-Tongji cohort study, China.
OBJECTIVE
To examine the association between nighttime sleep duration, sleep timing, and their interactive effect on falls among middle-aged and older Chinese adults.


METHODS
The study sample of 35,465 (mean age 64.5 years) subjects were from the Dongfeng-Tongji cohort. All subjects completed baseline questionnaires and medical examinations. Participants were classified into five groups based on nighttime sleep duration: <7 h, 7- ≤ 8 h, 8- ≤ 9 h, 9- ≤ 10 h, ≥10 h, and three groups based on sleep timing: <21:00, 21:00- ≤ 23:00, ≥23:00. Logistic regression models estimated the odds ratios (ORs) of nighttime sleep duration/timing with single/recurrent falls.


RESULTS
The one year rate of falls was 15.2 % among the subjects. After adjusting for potential confounders, participants with longer sleep duration (≥10 h) had 1.48 times (95 % confidence interval [CI], 1.11-1.97) higher odds of recurrent falls, compared with those sleeping 7- ≤ 8 h. Earlier (<21:00) and later (≥23:00) sleep timing were associated with recurrent falls (earlier: OR 1.90, 95 % CI 1.33-2.73; later: OR 1.33, 95 % CI 1.14-1.56) compared with a normal sleep schedule (sleep during 21:00- ≤ 23:00). The combined effect showed that longer sleep duration and earlier sleep timing were associated with a greater occurrence of falls (OR 1.66, 95 % CI 1.22-2.26).


CONCLUSIONS
Long nighttime sleep duration was associated with a higher occurrence of recurrent falls but not with a single fall. Long sleep duration with early timing greatly increased both single and recurrent falls. Geriatr Gerontol Int 2017; 17: 1886-1892.
Tongji Research Center for Injury Control, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|MOE Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Yi
Y
Wang
Tongji Research Center for Injury Control, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|MOE Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Wending
W
Li
Department of Maternal and Child Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|MOE Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Lijun
L
Shen
Tongji Research Center for Injury Control, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|Department of Maternal and Child Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Lulu
L
Song
Department of Maternal and Child Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|MOE Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Hui
H
Li
Tongji Research Center for Injury Control, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|Department of Maternal and Child Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Bingqing
B
Liu
Department of Occupational and Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|MOE Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Jing
J
Yuan
Tongji Research Center for Injury Control, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|Department of Maternal and Child Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.|MOE Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Youjie
Y
Wang
D000058:Accidental Falls / Q000706:statistics & numerical data*; D000368:Aged; D002681:China; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D006801:Humans; D008875:Middle Aged; D012890:Sleep; D013997:Time Factors
falls; interactive effect; nighttime sleep duration; sleep timing