TABLE 2.
Baseline characteristics by dietary GI quintile and incidence of insomnia 3 y later, categorical variables1
| Dietary GI quintiles | Incident insomnia 3 y later | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Baseline characteristics | n | 1 (Low) | 2 | 3 | 4 | 5 (High) | P 2 | Yes | No | P 2 |
| Total n | 53,069 | 10,613 | 10,614 | 10,614 | 10,614 | 10,614 | 9783 | 43,286 | ||
| Insomnia n | 9783 | 1728 | 1924 | 1943 | 2065 | 2123 | <0.0001 | 9783 | 43,286 | |
| Median GI | 47.0 | 49.8 | 51.7 | 53.5 | 56.3 | |||||
| Race/ethnicity, % | <0.0001 | 0.0079 | ||||||||
| American Indian/Alaskan Native | 730 | 1.4 | 1.4 | 1.2 | 1.3 | 1.6 | 1.4 | 1.4 | ||
| Asian/Pacific Islander | 1653 | 2.3 | 3.1 | 3.8 | 3.7 | 2.6 | 2.5 | 3.3 | ||
| Black | 3474 | 4.7 | 4.3 | 5.4 | 6.8 | 11.6 | 6.3 | 6.6 | ||
| Hispanic | 1543 | 3.5 | 2.9 | 2.7 | 2.9 | 2.5 | 3.0 | 3.0 | ||
| White not of Hispanic origin | 45,528 | 87.7 | 87.9 | 86.8 | 85.1 | 81.4 | 86.5 | 85.6 | ||
| Missing race/ethnicity | 141 | 0.3 | 0.3 | 0.2 | 0.3 | 0.3 | 0.3 | 0.3 | ||
| Education ≥college grad, % | 24,350 | 52.8 | 50.4 | 47.9 | 43.2 | 35.2 | <0.0001 | 42.4 | 46.7 | <0.0001 |
| Annual income ≥$50,000, % | 21,941 | 48.0 | 45.7 | 43.8 | 41.1 | 36.7 | <0.0001 | 40.5 | 43.7 | <0.0001 |
| Live alone, % | 14,040 | 28.7 | 27.5 | 26.2 | 25.2 | 24.7 | <0.0001 | 25.8 | 26.6 | 0.1680 |
| Live with husband or partner, % | 33,934 | 62.8 | 64.1 | 64.7 | 64.8 | 63.4 | 0.0003 | 65.3 | 63.6 | 0.0060 |
| Live with children, % | 5403 | 8.3 | 8.9 | 9.6 | 11.5 | 12.7 | <0.0001 | 10.3 | 10.2 | 0.9117 |
| Smoking status, % | <0.0001 | <0.0001 | ||||||||
| Never smoked | 27,042 | 48.5 | 51.6 | 52.4 | 52.2 | 50.5 | 48.6 | 51.5 | ||
| Past smoker | 22,429 | 45.6 | 43.0 | 41.7 | 40.6 | 40.5 | 44.3 | 41.8 | ||
| Current smoker | 2993 | 4.6 | 4.4 | 5.1 | 6.2 | 7.8 | 5.8 | 5.6 | ||
| Missing smoking | 605 | 1.4 | 1.0 | 1.2 | 1.0 | 1.2 | 1.3 | 1.1 | ||
| Alcohol intake, % | <0.0001 | <0.0001 | ||||||||
| Nondrinker | 5428 | 7.9 | 8.2 | 9.7 | 11.1 | 14.1 | 9.7 | 10.3 | ||
| Past drinker | 9010 | 15.6 | 14.8 | 16.0 | 17.7 | 20.8 | 18.5 | 16.6 | ||
| <1 drink/mo | 6108 | 9.5 | 10.0 | 11.5 | 11.8 | 14.7 | 12.0 | 11.4 | ||
| <1 drink/wk | 10,820 | 19.3 | 20.8 | 20.4 | 21.1 | 20.3 | 20.4 | 20.4 | ||
| 1 to <7/wk | 14,393 | 28.7 | 30.7 | 29.0 | 26.6 | 20.7 | 26.1 | 27.4 | ||
| ≥7/wk | 7061 | 18.3 | 15.0 | 13.1 | 11.3 | 8.8 | 12.8 | 13.4 | ||
| Missing alcohol | 249 | 0.6 | 0.5 | 0.4 | 0.5 | 0.5 | 0.5 | 0.5 | ||
| Caffeine, % | <0.0001 | 0.2737 | ||||||||
| Quintile 1 | 10,613 | 21.5 | 19.8 | 19.6 | 19.5 | 19.5 | 20.0 | 20.0 | ||
| Quintile 2 | 10,614 | 20.5 | 20.6 | 20.2 | 20.0 | 18.7 | 20.1 | 20.0 | ||
| Quintile 3 | 10,615 | 23.8 | 21.0 | 18.9 | 18.2 | 18.2 | 19.7 | 20.1 | ||
| Quintile 4 | 10,613 | 13.5 | 19.3 | 21.7 | 22.4 | 23.0 | 20.7 | 19.8 | ||
| Quintile 5 | 10,614 | 20.7 | 19.3 | 19.5 | 20.0 | 20.5 | 19.5 | 20.1 | ||
| Stressful life events, % | <0.0001 | <0.0001 | ||||||||
| Quintile 1 | 15,361 | 29.8 | 29.6 | 29.4 | 28.5 | 27.5 | 23.6 | 30.2 | ||
| Quintile 2 | 6792 | 12.8 | 13.2 | 13.1 | 12.9 | 12.0 | 10.2 | 13.4 | ||
| Quintile 3 | 8902 | 16.2 | 17.0 | 17.0 | 16.9 | 16.7 | 15.9 | 17.0 | ||
| Quintile 4 | 11,684 | 21.8 | 22.2 | 21.4 | 22.3 | 22.3 | 23.6 | 21.7 | ||
| Quintile 5 | 9396 | 17.4 | 16.5 | 17.1 | 17.5 | 20.0 | 25.1 | 16.0 | ||
| Missing stressful life events | 934 | 1.9 | 1.6 | 2.0 | 1.9 | 1.4 | 1.7 | 1.8 | ||
| Social support, % | <0.0001 | <0.0001 | ||||||||
| Quintile 1 | 10,969 | 20.0 | 19.6 | 20.8 | 20.6 | 22.3 | 25.3 | 19.6 | ||
| Quintile 2 | 10,924 | 20.4 | 20.9 | 20.6 | 20.8 | 20.2 | 21.7 | 20.3 | ||
| Quintile 3 | 10,362 | 19.0 | 20.2 | 19.6 | 19.5 | 19.3 | 18.0 | 20.0 | ||
| Quintile 4 | 10,552 | 20.4 | 20.2 | 19.4 | 20.2 | 19.2 | 18.5 | 20.2 | ||
| Quintile 5 | 9169 | 18.2 | 16.9 | 17.7 | 16.8 | 16.7 | 14.5 | 17.9 | ||
| Missing social support | 1093 | 2.0 | 2.1 | 1.9 | 2.0 | 2.4 | 2.0 | 2.1 | ||
| Depression, % | 3285 | 5.3 | 5.6 | 6.3 | 6.4 | 7.5 | <0.0001 | 9.5 | 5.4 | <0.0001 |
| Diabetes, % | 2375 | 4.4 | 4.4 | 4.3 | 4.6 | 4.7 | 0.9285 | 4.9 | 4.4 | 0.0296 |
| Hypertension, % | 16,104 | 28.1 | 28.8 | 30.6 | 31.3 | 32.9 | <0.0001 | 32.9 | 30.0 | <0.0001 |
| Myocardial infarction, % | 1051 | 1.9 | 1.6 | 1.8 | 2.2 | 2.4 | 0.0001 | 2.5 | 1.9 | 0.0004 |
| Cardiovascular disease, % | 8951 | 16.5 | 16.7 | 17.0 | 17.0 | 17.3 | 0.2214 | 19.6 | 16.3 | <0.0001 |
| Asthma, % | 3829 | 7.4 | 7.0 | 7.2 | 7.0 | 7.6 | 0.4081 | 8.8 | 6.9 | <0.0001 |
| Overactive thyroid, % | 1447 | 2.4 | 2.6 | 2.7 | 2.8 | 3.2 | <0.0001 | 3.0 | 2.7 | <0.0001 |
| Bodily pain, % | <0.0001 | <0.0001 | ||||||||
| None | 11,894 | 25.1 | 23.0 | 22.3 | 21.2 | 20.4 | 13.7 | 24.4 | ||
| Very mild | 20,967 | 39.8 | 40.4 | 39.8 | 39.5 | 38.0 | 33.7 | 40.8 | ||
| Mild | 10,321 | 18.0 | 19.3 | 19.4 | 20.3 | 20.3 | 23.0 | 18.7 | ||
| Moderate | 8254 | 14.3 | 14.3 | 15.4 | 15.9 | 18.0 | 23.4 | 13.8 | ||
| Severe | 1534 | 2.7 | 2.8 | 2.9 | 2.9 | 3.2 | 6.2 | 2.2 | ||
| Missing bodily pain | 99 | 0.2 | 0.2 | 0.1 | 0.2 | 0.2 | 0.1 | 0.2 | ||
| Hot flashes, % | <0.0001 | <0.0001 | ||||||||
| None | 42,764 | 82.7 | 83.0 | 80.8 | 79.7 | 76.9 | 77.4 | 81.3 | ||
| Mild | 7889 | 13.5 | 13.7 | 14.7 | 15.3 | 17.1 | 16.5 | 14.5 | ||
| Moderate | 1892 | 2.9 | 2.7 | 3.5 | 3.9 | 4.8 | 4.6 | 3.3 | ||
| Severe | 381 | 0.6 | 0.5 | 0.7 | 0.7 | 1.0 | 1.2 | 0.6 | ||
| Missing hot flashes | 143 | 0.3 | 0.2 | 0.3 | 0.4 | 0.2 | 0.3 | 0.3 | ||
| Hormone replacement therapy, % | 26,509 | 51.1 | 52.3 | 50.5 | 49.2 | 46.7 | <0.0001 | 50.9 | 49.8 | <0.0001 |
| Snoring, % | <0.0001 | <0.0001 | ||||||||
| Not in past 4 wk | 12,712 | 26.8 | 24.7 | 24.4 | 23.0 | 20.8 | 22.5 | 24.3 | ||
| Less than once a week | 2722 | 5.6 | 5.1 | 4.9 | 5.0 | 5.0 | 5.2 | 5.1 | ||
| 1 or 2 times/wk | 3282 | 6.0 | 5.9 | 6.6 | 6.4 | 6.1 | 5.9 | 6.3 | ||
| 3 or 4 times/wk | 2574 | 4.3 | 4.9 | 4.8 | 5.2 | 5.1 | 5.1 | 4.8 | ||
| ≥5 times/wk | 4792 | 7.6 | 7.8 | 8.5 | 9.9 | 11.4 | 10.3 | 8.7 | ||
| Don't know | 26,806 | 49.3 | 51.4 | 50.6 | 50.2 | 51.1 | 50.6 | 50.5 | ||
| Missing snoring | 181 | 0.4 | 0.3 | 0.3 | 0.3 | 0.4 | 0.4 | 0.3 | ||
1
GI, glycemic index.
2
Differences by depression and GI quintiles were tested with chi-square (χ2) tests for categorical variables.