Table 4.
Subgroup meta-analysis of cross-sectional studies.
| Short sleep duration | Long sleep duration | |||||||
|---|---|---|---|---|---|---|---|---|
| No. | OR (95% CI) | I2 | No. | OR (95% CI) | I2 | Pz | ||
| Sex | ||||||||
| Male | 7 | 1.05 (0.98, 1.12) | 46.0 | Ref. | 7 | 1.03 (0.99, 1.08) | 14.0 | Ref. |
| Female | 7 | 0.99 (0.89, 1.09) | 56.8 | 0.121 | 7 | 1.09 (1.00, 1.18) | 67.9 | 0.272 |
| P = 0.174b | P = 0.104 | |||||||
| Continent | ||||||||
| Asia | 19 | 1.08 (1.01, 1.17) | 75.8 | Ref. | 20 | 1.12 (1.05, 1.20) | 79.0 | Ref. |
| Europe | 6 | 1.03 (0.98, 1.08) | 20.8 | 0.271 | 6 | 1.17 (1.01, 1.36) | 64.6 | 0.583 |
| North America | 5 | 1.31 (0.99, 1.74) | 24.5 | 0.205 | 4 | 1.22 (0.75, 2.00) | 15.0 | 0.736 |
| South America | 1 | 1.70 (1.19, 2.44) | 0.0 | 0.016 | 1 | 1.08 (0.92, 4.26) | 0.0 | 0.147 |
| Africa | 1 | 0.96 (0.51, 1.81) | 0.0 | 0.708 | P = 0.171 | |||
| P = 0.173 | ||||||||
| Study population | ||||||||
| Community | 21 | 1.03 (0.98, 1.08) | 57.7 | Ref. | 22 | 1.14 (1.07, 1.21) | 65.9 | Ref. |
| Hospital | 5 | 1.36 (1.21, 1.53) | 45.7 | <0.001 | 5 | 1.10 (0.77, 1.59) | 91.6 | 0.885 |
| Company or office | 6 | 1.15 (0.93, 1.41) | 37.6 | 0.334 | 4 | 1.09 (0.93, 1.28) | 0.0 | 0.644 |
| P < 0.001 | P = 0.261 | |||||||
| Sleep measurement | ||||||||
| Questionnaire | 16 | 1.08 (0.99, 1.18) | 69.4 | Ref. | 15 | 1.11 (1.03, 1.20) | 87.6 | Ref. |
| Interview | 8 | 1.13 (1.04, 1.23) | 76.3 | 0.496 | 8 | 1.12 (1.01, 1.24) | 36.6 | 0.893 |
| Standard questionnaire | 6 | 1.02 (0.92, 1.13) | 0.0 | 0.363 | 6 | 1.13 (0.90, 1.40) | 81.1 | 0.947 |
| Objective | 2 | 0.92 (0.67, 1.28) | 0.0 | 0.349 | 2 | 1.27 (0.63, 2.56) | 28.3 | 0.733 |
| P = 0.012 | P = 0.021 | |||||||
| Definition of sleep duration | ||||||||
| <5 h short or > 9 h longc | 5 | 1.23 (0.98, 1.5) | 29.2 | Ref. | 7 | 1.09 (0.92, 1.29) | 67.3 | Ref. |
| <6 h short or > 8 h long | 13 | 1.13 (1.02, 1.24) | 82.4 | 0.492 | 17 | 1.18 (1.09, 1.27) | 53.6 | 0.405 |
| <7 h short or > 7 h long | 2 | 1.04 (0.98, 1.11) | 20.4 | 0.164 | 6 | 1.01 (0.92, 1.11) | 93.0 | 0.464 |
| <8 h short | 2 | 0.98 (0.90, 1.06) | 0.0 | 0.065 | P = 0.121 | |||
| P = 0.154 | ||||||||
| MetS measurement | ||||||||
| NECP ATP-III | 12 | 1.06 (0.98, 1.16) | 68.2 | Ref. | 10 | 1.07 (0.98, 1.15) | 73.8 | Ref. |
| Modified NECP ATP-III | 6 | 1.00 (0.94, 1.07) | 34.3 | 0.308 | 6 | 1.22 (1.15, 1.28) | 35.8 | 0.006 |
| AHA-NHLBI | 9 | 1.20 (1.03, 1.39) | 44.3 | 0.186 | 9 | 1.23 (1.01, 1.50) | 27.3 | 0.195 |
| IDF | 3 | 1.05 (0.88, 1.25) | 21.0 | 0.879 | 5 | 1.07 (1.01, 1.14) | 33.4 | 0.945 |
| Others | 2 | 1.40 (1.22, 1.61) | 14.1 | <0.001 | 1 | 0.98 (0.81, 1.19) | 10.1 | 0.426 |
| P < 0.001 | P < 0.001 | |||||||
| Sample size | ||||||||
| <5,000 | 23 | 1.07 (0.99, 1.06) | 49.7 | Ref. | 18 | 1.28 (1.12, 1.47) | 56.2 | Ref. |
| 5,000–20,000 | 5 | 1.09 (0.96, 1.25) | 57.4 | 0.842 | 8 | 1.05 (0.95, 1.15) | 82.0 | 0.018 |
| >20,000 | 4 | 1.11 (1.00, 1.23) | 51.3 | 0.638 | 5 | 1.09 (1.01, 1.18) | 82.1 | 0.044 |
| P = 0.004 | P < 0.001 | |||||||
| Study quality | ||||||||
| High | 7 | 1.03 (1.00, 1.06) | 26.9 | Ref. | 7 | 1.03 (0.97, 1.09) | 60.5 | Ref. |
| Low | 25 | 1.06 (1.03, 1.09) | 63.4 | 0.013 | 23 | 1.15 (1.06, 1.25) | 70.7 | 0.030 |
| P = 0.143 | P < 0.001 | |||||||
a
P-value of the two-sample z test for estimates between subgroups.
b
P-value for heterogeneity.
c
For effects of short sleep duration, this category included those who defined <5 h as short sleep duration. For effects of long sleep duration, this category included those who defined > 9 h as long sleep duration. The same meaning for the following terms.