Table 4.
Multivariable-adjusted ORs and 95% CIs of sleep outcomes by quartiles of calcium-to-magnesium ratio levels
| Quartiles of calcium-to-magnesium ratio | P trend | |||||
|---|---|---|---|---|---|---|
| Q1 (lowest) |
Q2 | Q3 | Q4 (highest) |
|||
| No. of participants | 991 | 991 | 991 | 991 | – | |
| No. of observations | 1,982 | 1,982 | 1,982 | 1,982 | – | |
| Outcome: sleep quality (ORs of better sleep quality score) | ||||||
| Model 1 | 1(Ref.) | 1.01 (0.89, 1.15) | 1.07 (0.93, 1.22) | 1.09 (0.95, 1.26) | 0.16 | |
| Model 2 | 1(Ref.) | 1.00 (0.88, 1.14) | 1.04 (0.91, 1.20) | 1.08 (0.93, 1.24) | 0.24 | |
| Model 3 | 1(Ref.) | 0.99 (0.87, 1.13) | 1.01 (0.88, 1.16) | 1.03 (0.89, 1.20) | 0.60 | |
| Outcome: sleep duration (ORs compared to the reference group: 7–9 h) | ||||||
| Model 1 | <7 h vs. ref | 1(Ref.) | 0.96 (0.84, 1.11) | 0.93 (0.81, 1.07) | 1.02 (0.88, 1.18) | 0.77 |
| >9 h vs. ref | 1(Ref.) | 0.69 (0.39, 1.25) | 0.92 (0.52, 1.62) | 1.30 (0.75, 2.27) | 0.24 | |
| Model 2 | <7 h vs. ref | 1(Ref.) | 1.01 (0.87, 1.17) | 0.92 (0.79, 1.08) | 1.01 (0.86, 1.18) | 0.92 |
| >9 h vs. ref | 1(Ref.) | 0.74 (0.41, 1.36) | 1.00 (0.56, 1.79) | 1.29 (0.73, 2.29) | 0.27 | |
| Model 3 | <7 h vs. ref | 1(Ref.) | 1.03 (0.89, 1.19) | 0.97 (0.83, 1.13) | 1.10 (0.93, 1.30) | 0.36 |
| >9 h vs. ref | 1(Ref.) | 0.80 (0.43, 1.48) | 1.12 (0.61, 2.06) | 1.68 (0.91, 3.12) | 0.07 | |
All models were constructed using generalized estimating equation method. P for trend was examined using the medians of Ca:Mg quartiles. The values of covariates, unless specified, were calculated as the cumulative average of repeated measurements by sleep quality at year 15 and year 20, respectively.
Model 1 was adjusted for age at baseline (continuous), sex (female or male), race (blacks or whites), study center, and time.
Model 2 was additionally adjusted for education (continuous), smoking status (current vs. no), alcohol consumption (continuous), BMI at baseline (<18.5, 18.5–24.9, 25–29.9, or ≥30 kg/m2), physical activity (continuous), and total calorie intake (quartiles).
Model 3 was additionally adjusted for caffeine intake (quartiles), vitamin D intake (quartiles), carbohydrate intake (quartiles).
Abbreviations: BMI, body mass index; Ca, calcium; CI, confidence interval; h, hours; Mg, magnesium; OR, odds ratio; Q, quartile; ref, reference.