The healthy worker effect in US chemical industry workers

Area of Science:

• Occupational Health
• Epidemiology
• Industrial Hygiene

Background:

• Occupational studies often report a 20% deficit in overall mortality, known as the healthy worker effect (HWE).
• Various analytical methods can address components of the HWE.

Purpose of the Study:

• To investigate the healthy worker effect within a contemporary industrial cohort.
• Examine mortality patterns in US chemical industry employees.

Main Methods:

• Calculated standardized mortality ratios (SMRs) for a cohort of 114,683 US chemical industry employees.
• Data collected for individuals employed for at least 3 days between 1960 and 2005.

Main Results:

• Overall mortality SMR was 79 (95% CI 78-80).
• Specific SMRs included 81 for heart disease, 70 for non-malignant respiratory disease, and 83 for combined smoking-related cancers.
• SMR for other cancers was 97 (95% CI 95-100).

Conclusions:

• The observed low standardized mortality ratios (SMRs) are likely attributed to differential smoking behaviors between the cohort and the general population.
• Future research on the HWE should consider and control for smoking prevalence.