Odds ratios and 95% CIs of modifiable risk factors in 2009 across age ranges of rotating night shift work (as recalled in 2009) in Nurses’ Health Study II
| Characteristic | Rotating night shift work categories at age ranges* | ||||
|---|---|---|---|---|---|
| Never worked night shifts (N=15 391) | Ever worked rotating night shifts at age 20–25 (N=20 022) | Ever worked rotating night shifts at age 26–35 (N=10 761) | Ever worked rotating night shifts at age 36–45 (N=5392) | Ever worked rotating night shifts at age 46+ (N=2885) | |
| OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | |
| Obese (body mass index ≥30 kg/m2) | – | – | – | – | – |
| N (cases/non-cases)† | 3822/11 218 | 5510/14 129 | 3412/7101 | 1764/3508 | 977/1839 |
| Model 1‡ | Ref | 1.00 (0.96 to 1.05) | 1.22 (1.16 to 1.28) | 1.08 (1.01 to 1.15) | 1.15 (1.06 to 1.26) |
| Model 2§ | Ref | 1.06 (1.02 to 1.11) | 1.25 (1.19 to 1.32) | 1.05 (0.98 to 1.13) | 1.12 (1.02 to 1.22) |
| Model 3¶ | Ref | 1.01 (0.96 to 1.06) | 1.19 (1.12 to 1.26) | 1.02 (0.94 to 1.10) | 1.11 (1.00 to 1.23) |
| Caffeine intake (≥131 mg)** | – | – | – | – | – |
| N (cases/non-cases)† | 6667/6665 | 9451/7694 | 5110/4020 | 2565/1945 | 1399/ 989 |
| Model 1‡ | Ref | 1.10 (1.05 to 1.14) | 1.09 (1.04 to 1.14) | 1.08 (1.01 to 1.16) | 1.18 (1.07 to 1.29) |
| Model 2†† | Ref | 1.08 (1.04 to 1.13) | 1.05 (0.99 to 1.10) | 1.04 (0.97 to 1.12) | 1.16 (1.06 to 1.27) |
| Total Calories (≥1715 kcal/day)** | – | – | – | – | – |
| N (cases/non-cases)† | 6666/6666 | 9272/7873 | 4949/4181 | 2508/2002 | 1374/1014 |
| Model 1‡ | Ref | 1.09 (1.05 to 1.14) | 1.05 (1.00 to 1.10) | 1.09 (1.02 to 1.17) | 1.20 (1.09 to 1.31) |
| Model 2‡‡ | Ref | 1.06 (1.02 to 1.11) | 1.03 (0.98 to 1.08) | 1.09 (1.01 to 1.16) | 1.15 (1.05 to 1.26) |
| Current smoker | – | – | – | – | – |
| N (cases/non-cases)† | 764/14 627 | 1130/18 892 | 747/10 014 | 433/4959 | 220/2665 |
| Model 1‡ | Ref | 0.96 (0.89 to 1.04) | 1.17 (1.07 to 1.28) | 1.26 (1.12 to 1.42) | 1.10 (0.94 to 1.28) |
| Model 2§§ | Ref | 0.98 (0.91 to 1.07) | 1.19 (1.08 to 1.30) | 1.23 (1.09 to 1.39) | 1.03 (0.88 to 1.20) |
| Average sleep (≤7 h)¶¶ | – | – | – | – | – |
| N (cases/non-cases)† | 9233/5595 | 12 948/6432 | 6937/3449 | 3517/1682 | 1986/796 |
| Model 1‡ | Ref | 1.13 (1.08 to 1.17) | 1.04 (0.99 to 1.09) | 1.03 (0.96 to 1.10) | 1.33 (1.21 to 1.45) |
| Model 2*** | Ref | 1.13 (1.08 to 1.17) | 1.04 (0.99 to 1.09) | 1.03 (0.96 to 1.10) | 1.33 (1.22 to 1.46) |
*The number of women in ever rotating night shifts by age range does not include nights only shift work and women can be in multiple age ranges when night shift work was performed.
†N's vary due to missing data among modifiable risk factors.
‡Adjusted for age (5 years), education level of the nurse's spouse/partner (≤high school, 2-year or 4-year college, graduate school or not married/missing), primary night only shift work at age 20–25, 26–35, 36–45, 46+ (yes, no at each age-range).
§Adjusted for model 1 covariates plus physical activity (quintiles, met-hour/week) and chronotype (definitely a morning type, more of a morning than evening type, more of an evening than morning type, definitely an evening type and neither).
¶Adjusted for model 2 covariates plus body mass index at age 18 (<18.5, 18.5 to <20, 20 to <22.5, 22.5 to <25, 25 to <27.5, ≤27.5 kg/m2).
**Assessed in 2007 and median value based on never night shift workers.
††Adjusted for model 1 covariates plus total calories (quintiles, kcal/day) and smoking status (never, past, current smoker).
‡‡Adjusted for model 1 covariates plus physical activity (quintiles, met-hour/week), body mass index (18.5 to <25, 25 to <30, ≤30 kg/m2), caffeine intake (mg), smoking status (never, past, current smoker), chronotype (definitely a morning type, more of a morning than evening type, more of an evening than morning type, definitely an evening type and neither).
§§Adjusted for model 1 covariates plus physical activity (quintiles met-hour/week), body mass index (18.5 to <25, 25 to <30, ≤30 kg/m2), caffeine intake (quintiles, mg), alternative healthy eating index (quintiles), and chronotype (definitely a morning type, more of a morning than evening type, more of an evening than morning type, definitely an evening type and neither).
¶¶Average hours of sleep over a 24-hour period.
***Adjusted for model 1 covariates plus chronotype (definitely a morning type, more of a morning than evening type, more of an evening than morning type, definitely an evening type and neither).