The healthy/unhealthy worker effect as a phenomenon of occupational selection and the causation problem

Today, the "healthy worker effect" is understood as organized (on the part of the employer) and/or unorganized (self-selection on the part of the worker, due to the functional capabilities and the state of workers’ health) professional selection of healthier workers in unfavorable working conditions, who remain in the profession. It represents one of the most important problems in epidemiological research in occupational medicine. The “healthy worker effect” and its intensity in various industries (in various professions) can indirectly characterize the harmful and unfavorable conditions. The “healthy worker effect” and its intensity determine the need for medical and social security, as well as rehabilitation measures, not only for people who remain in this production (in this profession), but also for people who left this production or specialty, to prevent the phenomenon of increased mortality among workers who left a given production or profession due to suspension from work based on the results of periodic medical examinations and self-selection, or due to intolerance to working conditions because of the state of health.

Epidemiological research in industrial medicine: the healthy / unhealthy worker effect and problems of causality

The author investigates issues related to the professional ability of a person, analyzes the current state of terminology, including the terms "healthy worker effect", "healthy migrant effect", concludes that it is necessary to unify the scientific and medical terminology used in scientific research into the "healthy worker effect.

Unfit Assessments of Class 1 Medical Certificate Holders

INTRODUCTION: An aviation safety management system should consider and mitigate against all potential risks to flight safety. In addition to in-flight incapacitation, pilots falling below regulatory standards who are assessed as unfit may have represented a risk prior to that assessment. An analysis was undertaken of Class 1 certificate holders to determine factors correlated with unfit assessments.METHODS: Fitness assessments of pre-existing Class 1 certificate holders following medical examinations (to EASA Part-MED standards) or between medicals were studied between 1 January 2016 and 31 December 2019. Assessments where the outcome was ‘fit’ (N= 99,406) were compared with those where the outcome was ‘unfit’ (N= 7925). Analyses for correlation between unfit assessments against age, declared coexisting medical conditions, and the number of days since last assessed as fit were undertaken using SPSS.RESULTS: Unfit assessment likelihood and age were strongly correlated; there is, however, evidence for the ‘healthy worker effect’, with a fall in unfit assessments between 60–65 yr of age. There was no association between coexisting medical condition declaration and the likelihood of becoming unfit. The time interval between a fit and unfit assessment was significantly lower when comparing 20–60 and 61–63 yr old individuals.DISCUSSION: The analysis of unfit assessments shows strong correlation with increasing age and the possible presence of the healthy worker effect among commercial pilots. The decreased time from a previous fit assessment to an unfit assessment supports the reduced certificate validity period of Class 1 applicants over 60 yr of age.Cairns MK. Unfit assessments of Class 1 Medical certificate holders. Aerosp Med Hum Perform. 2021; 92(12):945–949

Mortality risk factors among National Football League players: An analysis using player career data

In general, National Football League (NFL) players tend to live longer than the general population. However, little information exists about the long-term mortality risk in this population. Frequent, yet mild, head trauma may be associated with early mortality in this group of elite athletes. Therefore, career playing statistics can be used as a proxy for frequent head trauma. Using data from Pro Football Reference, we analyzed the association between age-at-death, position, and NFL seasons-played among 6,408 NFL players that were deceased as of July 1, 2018. The linear regression model allowing for a healthy worker effect demonstrated the best fit statistics (F-statistic = 9.95, p-value = 0.0016). The overall association of age-at-death and seasons-played is positive beginning at the 10.75 and 10.64 seasons-played point in our two models that feature seasons-played and seasons-played squared as explanatory variables. Previous research that does not account for this survivorship bias/healthy worker effect may not adequately describe mortality risk among NFL players.

A comprehensive review of the healthy worker effect in occupational epidemiological studies

The reduction of mortality and morbidity rates among occupational cohort studies may be attributed to the presence of the healthy worker effect (HWE). Occupational epidemiologic studies investigating worker’s health are prone to the risk of having the HWE phenomenon and this special form of bias has been debated over the years. Hence, it’s imperative to explore in-depth the magnitude and sources of HWE, and further, elucidate the factors that may affect HWE and strategies reducing HWE. The HWE should be considered as a mixed bias between selection and confounding bias. The validity threats due to the HWE among morbidity studies are the same as the mortality studies. The consequent reduction due to the HWE in the association between the exposure and outcome may lead to underestimating some harmful exposures in the workplace or occupational settings. Healthy hire effect and healthy worker survivor effect are the main sources of HWE. Several factors can increase or decrease the probability of HWE; therefore, the investigators should consider them among future occupational epidemiological studies. Many strategies can help in reducing the impact of HWE, but each strategy has its weaknesses and strengths. Not all strategies can be applied among all occupational epidemiological studies. Mathematical procedures still need further investigations to be validated. HWE is a consequence of inappropriate comparison groups in nature. The usage of the general population as a reference group is not an appropriate choice. By considering the HWE sources and factors and using appropriate strategies, the impact of HWE may be reduced.

Mortality risk factors among National Football League players: An analysis using player career data

In general, National Football League (NFL) players tend to live longer than the general population. However, little information exists about the long-term mortality risk in this population. Frequent, yet mild, head trauma may be associated with early mortality in this group of elite athletes. Therefore, career playing statistics can be used as a proxy for frequent head trauma. Using data from Pro Football Reference, we analyzed the association between age-at-death, position, and NFL seasons-played among 6,408 NFL players that were deceased as of July 1, 2018. The linear regression model allowing for a healthy worker effect demonstrated the best fit statistics (F-statistic = 9.95, p-value = 0.0016). The overall association of age-at-death and seasons-played is positive beginning at the 10.75 and 10.64 seasons-played point in our two models that feature seasons-played and seasons-played squared as explanatory variables. Previous research that does not account for this survivorship bias/healthy worker effect may not adequately describe mortality risk among NFL players.

A priori assessment of the intensity of self-selection phenomena in professional groups

The analysis of the published data and the expert evaluation of the factors affecting the turnover of the personnel in industrial populations and the formation of «healthy worker effect. A computer program has been created on the basis of the studies providing an approximate assessment of the intensity of the self-selection.

Respiratory health, occupation and the healthy worker effect

Background Workers are exposed to physical, chemical and other hazards in the workplace, which may impact their respiratory health. Aims To examine the healthy worker effect in the Canadian working population and to identify the association between occupation and respiratory health. Methods Data from four cycles of the Canadian Health Measures Survey were utilized. The current occupation of employed participants was classified into 10 broad categories based on National Occupation Category 2011 codes. Data relating to 15 400 subjects were analysed. Results A significantly lower proportion of those in current employment than those not in current employment reported respiratory symptoms or diseases or had airway obstruction. Similarly, those currently employed reported better general health and had greater mean values for percent-predicted forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory flow between 25% and 75% of FVC (FEF25–75%) and FEV1/FVC ratio. Among males, females and older age groups, significant differences were observed for almost all the respiratory outcomes for those in current employment. Those in ‘Occupations unique to primary industry’ had a significantly greater likelihood of regular cough with sputum and ever asthma and had lower mean values of percent-predicted FEV1/FVC and FEF25–75% than those in ‘Management occupations’. Those in ‘Health occupations’ had the highest proportion of current asthma. Conclusions Participants in current employment were healthier than those not in current employment providing further support for the healthy worker effect. Those in ‘Occupations unique to primary industry’ had an increased risk of adverse respiratory outcomes and reducing workplace exposures in these occupations has the potential to improve their respiratory health.