Table 3. Shift Work and Risk of Coronary Heart Disease (CHD) in the NHS2.
A total of 3,519 CHD cases (i.e. nonfatal myocardial infarction, CHD-attributed death, angiogram-confirmed angina pectoris, angioplasty, coronary artery bypass graft surgery, and coronary artery stents) occurred during 24 years of follow-up in NHS2 (n=115,535). Results represent hazard ratios (HR) with 95% confidence intervals (95%CI).
| None | <5 years | 5 to 9 years | ≥ 10 years | p for trenda | p for interaction shift work * timeb | |
|---|---|---|---|---|---|---|
| NHS2 – Baseline history of rotating night shift workc | ||||||
| cases/person-years | 1,236 /1,007,860 | 1,673/1,296,585 | 347/226,580 | 263/132,971 | ||
| Incidence Rated per 100,000 person/years (95%) | 122.6 (105.0-140.3) | 130.6 (114.5-146.7) | 151.6 (109.2-194.0) | 178.0 (123.0-234.0) | ||
| Age-adjusted Model (HR, 95%CI) | 1.00 (Ref) | 1.06 (0.99-1.14) | 1.22 (1.08-1.38) | 1.34 (1.17-1.53) | <0.001 | |
| Multivariable-adjusted Modele (HR, 95%CI) | 1.00 (Ref) | 1.05 (0.97-1.13) | 1.12 (0.99 -1.26) | 1.15 (1.01-1.32) | 0.01 | 0.54 |
| Restricted to MI and CHD death | ||||||
| cases/person-years | 151 /1,018,680 | 161/1,311,173 | 38/229,694 | 35/135,197 | ||
| Incidence Rated per 100,000 person/years (95%) | 14.8 (9.5-20.2) | 12.4 (7.9-16.9) | 16.2 (4.3-28.0) | 24.4 (7.2-41.6) | ||
| Multivariable-adjusted Modele (HR, 95%CI) | 1.00 (Ref) | 0.83 (0.66-1.04) | 0.98 (0.69-1.41) | 1.09 (0.75-1.59) | 0.71 | 0.55 |
| NHS2 – Updated shift workf | ||||||
| cases/person-years | 589/554,846 | 1,077/872,476 | 328/222,286 | 233/118,813 | ||
| Incidence Rated per 100,000 person/years (95%CI) | 115.8 (91.2-140.4) | 137.4 (116.2-158.6) | 161.9 (116.3-207.6) | 190.5 (125.1-255.8) | ||
| Age-adjusted Model (HR, 95%CI) | 1.00 (Ref) | 1.18 (1.06-1.30) | 1.40 (1.22-1.61) | 1.59 (1.36-1.85) | <0.001 | |
| Multivariable-adjusted Modele (HR, 95%CI) | 1.00 (Ref) | 1.12 (1.01-1.24) | 1.19 (1.04-1.37) | 1.27 (1.09-1.48) | 0.001 | 0.84 |
Based on category mid-points, except for 10+ years, where the mid-point was set to 10 years.
Based on the interaction between shift work category mid-points (except for 10+ years, where the mid-point was set to 10 years) and time (in 2-year cycles).
Assessed in 1989.
Incidence rates and confidence intervals are standardized relative to the age distribution of women who reported no history of rotating night shift work, separately for each cohort.
Multivariable-adjusted model including age, physical activity (METs/h per week, in quintiles), diet (Alternative Healthy Eating Index [AHEI] score, Chiuve et al., 2012, in quintiles), alcohol consumption (none, 0.1-5, 5.1-10, 10.1-20, >20g/day) and pack-years of smoking (continuous), parental history of MI <60yrs (yes/no), menopausal status (pre/post), parity (nulliparous, 1 child, 2 children, ≥3 children), post-menopausal hormone use (ever, never, pre-menopausal), multivitamin use (yes/no), acetaminophen use (yes/no), NSAIDs use (yes/no) and aspirin use (yes/no), hypertension (yes/no), hypercholesterolemia (yes/no), diabetes (yes/no), body mass index (< 25, 25-29.9, 30-34.9, ≥35), race (white, black, other), and husbands' highest educational level (up to high school diploma, college degree, graduate school level or similar).
Updated shift work refers to cumulative duration of rotating night shift work women reported until 2007.