Healthy volunteer effect in industrial workers.

Area of Science:

• Epidemiology
• Occupational Health
• Biostatistics

Background:

• The healthy volunteer effect (HVE) is a known bias in epidemiological research where volunteers exhibit lower mortality rates than non-volunteers.
• Similarly, the healthy worker effect (HWE) shows reduced mortality in occupationally active individuals compared to the general population.

Purpose of the Study:

• To investigate the presence and duration of the healthy volunteer effect (HVE) among occupationally active individuals.
• To determine if HVE influences mortality rates in male industrial employees participating in screening examinations.

Main Methods:

• Followed a cohort of Israeli male industrial employees for 8 years, comparing mortality between participants (71.6%) and non-participants in cardiovascular disease screening.
• Calculated standardized mortality ratios (SMRs) against the general population and used a proportional hazard model to adjust for confounding factors like age and factory size.

Main Results:

• The overall cohort SMR was 78%, with participants showing an SMR of 71% and non-participants 99%.
• After adjusting for age and factory size, the all-cause mortality hazard ratio for participants versus non-participants was 0.69 (95% CI = 0.51-0.94).
• Age-adjusted death rates per 10,000 person-years were consistently lower for participants (39.6 initially, 30.0 finally) than non-participants (58.6 initially, 51.5 finally).

Conclusions:

• The healthy volunteer effect (HVE) is present in occupationally active populations.
• This HVE bias can persist for at least 8 years, impacting epidemiological study findings in industrial workers.