| Author, Date |
Sample |
Measure of Overtime |
Cardiovascular Measure |
Statistical Methods Controls |
Results Reported by Authors |
| Hayashi et al.1996 |
Compared three groups of male white collar workers at one electronics plant:
Group sizes: 10 - 19
Group M ages 36 - 47
Japan |
One month daily diary of work hours (overtime hours/month by group):
Comparison 1 with normal BP:
- High overtime: 88 +/- 42
- Low overtime: 25 +/- 7
Comparison 2 with elevated BP:
- High overtime: 84 +/- 42
- Low overtime: 26 +/- 7
Comparison 3 with workers examined twice during busy and slow season:
- High overtime: 96 +/- 28
- Low overtime: 43 +/- 18
|
24-h blood pressure and heart rate measured every hour with portable monitor:
- Normal BP:systolic < 140; diastolic < 85
- Elevated BP: systolic >140 to <160; diastolic > 90 to < 105 |
- t-test for independent samples tested the repeated measures of BP and pulse readings
- Paired t-test tested seasonal group
|
In Comparison 1 with normal BP, high overtime showed:
- Higher average systolic and diastolic BP
- Heart rate NS
In Comparison 2 with elevated BP, high overtime showed:
- Higher average diastolic BP and heart rate
- Systolic BP NS
In Comparison 3, workers during busy season showed:
- Higher average systolic and diastolic BP
- Higher heart rates |
| Iwasaki et al.1998 |
71 salesman:
- Age R 22 - 60
- Japan |
One-time survey*:
- Short work hours-57 h/wk
- Long work hours-61 to 68 h/wk
* Work hours defined as hours in office plus commute time during last month |
During one evening measured mean of two blood pressure readings. |
t-test |
Mean systolic blood pressure elevated for long-hour group as compared with short-hour group for ages 50 - 60, and no difference noted for ages 20 - 49. |
| Liu et al.2001 |
- 260 men with acute myocardial infarction (AMI)
- 445 male controls
- Age R 40 - 79
- White collar and blue collar workers
- Japan |
One-time interview:
- Work h/wk:<= 40; 41 - 60; >= 61
- Days off/month: < 2; 2 - 7; >= 8
- Rotating shifts yes/no
- Interactions: work hours and sleep length; work hours and days off/month |
- Hospital records identified cases with AMI who survived to receive rehabilitation from 1996 to 1998.
- Controls free of AMI: resident registers used to match for age, sex, residence.
- Other measures:
Workday sleep hours: <= 5; 6 - 8; >= 9
Days off sleep hours: <= 5; 6 - 8; >=9 h
Days/wk with < 5h sleep |
- ANOVA
- ANACOVA
- Logistic regression analysis: interaction of sleep with working hours assessed with likelihood ratio test
- Covariates: hypertension, diabetes, hyperlipidaemia, overweight, cigarette smoking, parental coronary heart disease, blue collar/white collar job, sedentary job |
- Working > 61 h/wk increased risk by two fold for AMI compared with <= 40 h (CI 1.1 - 3.5).
- < 2 days off in previous month increased risk (OR 2.9; CI 1.3 - 6.5).
- Categories of longer work and less days off or short sleep time showed trend for increase in the OR, but none of interactions were significant. |
| Nakanishi et al.2001b |
941 male white collar workers fromone building contractor:
- No history of hypertension (HTN) Age R 35 - 54
- Japan |
Interview in 1994: work h/day < 8.0; 8.0 - 8.9; 9.0 - 9.9; 10.0 - 10.9; >= 11.0 |
- BP measurements during annual health exam from 1994 to 1999
- World Health Organization criteria for HTN:
- Systolic blood pressure >= 160 mm Hg
- Diastolic blood pressure >= 95 mm Hg
- Taking BP medication |
- ANOVA
- Cox proportional hazard method: covariates (measured 1994): age, occupation, position, BMI, alcohol intake, commute time, vegetable and salt intake, eating breakfast, smoking, exercise, sleep length. |
- 336 men developed borderline HTN or definite HTN
- 88 men developed definite HTN
- Relative risk for borderline HTN or definite HTN (reference category < 8 h/day):
- 10 - 10.9 h/day .63 (CI .43 - .91)
- >11.0 h/day .48 (CI .31 - .74)
- Relative Risk for definite HTN:
>11h/day .33 (CI.11 - .95) |
| Park et al.2001a |
238 male engineers from 3 electronics manufacturing plants:
- Age M 32, R 22 - 46
- South Korea |
One-time questionnaire: M h/wk during previous month (R 52 - 89 h/wk) |
Blood pressure on afternoon of the survey day |
- Correlation coefficients
- Multiple linear regression
- Covariates: age and hours of sleep |
Weekly working hours showed no significant correlation with blood pressure. |
