Table 2 Prevalence and adjusted OR (95% CI) of depressive symptoms by groups of napping frequency and duration, and Pittsburgh Sleep Quality Index components and global sleep quality

Napping frequency

 Non-nappers

6699 (4.6)

1.00

1.00

1.00

 1–3 days/week

2306 (4.8)

1.13 (0.90, 1.41)

1.11 (0.89, 1.40)

1.11 (0.88, 1.40)

 4–6 days/week

1500 (4.6)

1.14 (0.87, 1.50)

1.12 (0.85, 1.47)

1.10 (0.83, 1.45)

 daily

6281 (6.4)

1.41 (1.20, 1.65)***

1.38 (1.18, 1.62)***

1.38 (1.17, 1.62)***

 P for trend

< 0.001

< 0.001

< 0.001

Napping duration

 Non-nappers

6699 (4.6)

1.00

1.00

1.00

 < 60 min

3311 (5.4)

1.24 (1.02, 1.51)*

1.23 (1.01, 1.49)*

1.22 (1.01, 1.49)*

 60–90 min

5561 (5.5)

1.26 (1.08, 1.49)**

1.23 (1.04, 1.46)*

1.24 (1.03, 1.45)*

 > 90 min

1093 (8.0)

1.72 (1.33, 2.21)***

1.67 (1.30, 2.16)***

1.68 (1.30, 2.18)***

 P for trend

< 0.001

< 0.001

< 0.001

 Good

14,213 (4.1)

1.00

1.00

1.00

 Poor

2575(12.2)

3.02 (2.60, 3.50)***

2.97 (2.55, 2.45)***

2.98 (2,57, 3.47)***

 P

< 0.001

< 0.001

< 0.001

Sleep latency

 ≤30 min

14,544 (4.5)

1.00

1.00

1.00

 31–60 min

1670 (8.6)

1.74 (1.43, 2.11)***

1.71 (1.41, 2.08)***

1.70 (1.40, 2.06)***

 > 60 min

574 (14.6)

3.03 (2.35, 3.90)***

3.02 (2.34, 3.89)***

3.01 (2.33, 3.88)***

 P for trend

< 0.001

< 0.001

< 0.001

Sleep duration

 < 5 h/day

893 (11.0)

2.32 (1.81, 2.97)***

2.28 (1.78, 2.92)***

2.31 (1.80, 2.96)***

 5–6 h/day

6503 (6.7)

1.58 (1.36, 1.84)***

1.59 (1.36, 1.85)***

1.59 (1.36, 1.85)***

 7–8 h/day

7917 (4.0)

1.00

1.00

1.00

 > 8 h/day

843 (2.7)

0.67 (0.43, 1.03)

0.66 (0.43, 1.03)

0.67 (0.44, 1.04)

 P for trend

< 0.001

< 0.001

< 0.001

Sleep efficiency

 ≥85%

11,348 (4.1)

1.00

1.00

1.00

 75–84%

2664 (6.9)

1.54 (1.29, 1.85)***

1.54 (1.29, 1.85)***

1.54 (1.28, 1.85)***

 65–74%

1403 (8.3)

1.88 (1.51, 2.34)***

1.85 (1.49, 2.29)***

1.86 (1.50, 2.31)***

 < 65%

1373 (9.3)

1.98 (1.60, 2.45)***

1.94 (1.57, 2.40)***

1.94 (1.57, 2.39)***

 P for trend

< 0.001

< 0.001

< 0.001

Sleep disturbances

 Not at all/<once per week

16,416 (4.7)

1.00

1.00

1.00

 At least once per week

372 (29.8)

6.51 (5.08, 8.34)***

6.41 (5.00, 8.21)***

6.35 (4.95, 8.14)***

 P

< 0.001

< 0.001

< 0.001

Sleep medications

 Not at all/<once per week

16,415 (5.1)

1.00

1.00

1.00

 At least once per week

373 (13.4)

2.99 (2.18, 4.12)***

2.88 (2.09, 3.96)***

2.91 (2.12, 4.01)***

 P

< 0.001

< 0.001

< 0.001

Daytime dysfunction

 Not at all/<once per week

15,576 (3.9)

1.00

1.00

1.00

 At least once per week

1212 (23.5)

6.53 (5.55, 7.68)***

6.47 (5.50, 7.61)***

6.42 (5.46, 7.56)***

 P

< 0.001

< 0.001

< 0.001

 Good (PSQI< 6)

11,432 (2.8)

1.00

1.00

1.00

 Poor (PSQI≥6)

5356 (10.7)

3.60 (3.12, 4.17)***

3.56 (3.08, 4.12)***

3.56 (3,07, 4.11)***

 P

< 0.001

< 0.001

< 0.001