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.

Prevalência de depressão em bombeiros / Prevalence of depression among firefighters / Prevalencia de depresión en bomberos

A depressão apresenta alta carga de doença no mundo. Fatores socioeconômicos e exposição a situações extremas no trabalho podem estar associados à doença. O objetivo do trabalho é investigar a prevalência e fatores associados à depressão em bombeiros de Belo Horizonte, Minas Gerais, Brasil. Estudo transversal foi realizado em universo de bombeiros do sexo masculino em Belo Horizonte (n = 711). O Inventário Beck para Depressão (IBD) foi utilizado para avaliar a presença de depressão. Modelos de regressão logística (uni e multivariada) foram utilizados para estudar a associação entre características sociodemográficas, estressores ocupacionais, situação de saúde e depressão. A prevalência de depressão na amostra estudada foi 5,5%. A chance de depressão foi maior entre bombeiros que relataram sintomas de estresse pós-traumático (OR = 12,47; IC95%: 5,64-27,57) e uso abusivo de álcool (OR = 5,30; IC95%: 2,35-11,96). Os resultados são discutidos considerando as inter-relações entre transtornos mentais, o efeito do trabalhador sadio e o reconhecimento social do trabalho dos bombeiros.

Depression burder is high worldwide. Socioeconomic factors and exposure to extreme situations at work may be associated with the illness. This study focused on the prevalence of depression and associated factors among firefighters in Belo Horizonte, Minas Gerais State, Brazil. A cross-sectional study was conducted among male firefighters in Belo Horizonte (n = 711). The Beck Depression Inventory (BDI) was used to assess depression. Univariate and multivariate logistic regression models were used to study the association between socio-demographic characteristics, occupational stressors, health status, and depression. Prevalence of depression in the sample was 5.5%. The likelihood of developing depression was higher among firefighters who reported post-traumatic stress symptoms (OR = 12.47; 95%CI: 5.64-27.57) and alcohol abuse (OR = 5.30; 95%CI: 2.35-11.96). The results are discussed considering the interrelationships between mental disorders, the healthy worker effect, and social recognition of firefighters' work.

La depresión tiene una alta carga como enfermedad mundial. Factores socioeconómicos y la exposición a situaciones extremas en el trabajo pueden estar asociados con la enfermedad. El objetivo de este trabajo es investigar la prevalencia y los factores asociados con la depresión en los bomberos de Belo Horizonte, Minas Gerais, Brasil. Se trata de un estudio transversal, realizado entre los bomberos de sexo masculino de Belo Horizonte (n = 711). Se utilizó el Inventario de Depresión de Beck (IDB) para evaluar la presencia de depresión. Se utilizaron modelos de regresión logística para estudiar la asociación entre características sociodemográficas, estrés ocupacional, estado de salud y depresión. La prevalencia de depresión fue de un 5,5%. La posibilidad de depresión fue mayor entre los bomberos que informaron síntomas de estrés postraumático (OR = 12,47; IC95%: 5,64-27,57) y abuso de alcohol (OR = 5,30, IC95%: 2,35-11,96). Los resultados son discutidos considerando las interrelaciones entre los trastornos mentales, el efecto en trabajadores sanos y el reconocimiento social de la labor de bomberos.

Comparison of Cardiovascular Disease Status Between Large Scale Industry Office and Self Employed Male Workers / 대한산업의학회지

OBJECTIVES: The aim of this study is to compare the cardiovascular disease status between large scale industry office and self employed male workers who have gaps in their intensive health management. METHODS: The cross sectional study was carried out with subjects composed of 244 shipyard office male workers and 381 self employed male workers, aged 30 to 55 years. They were given a health exam in a general hospital from January 2007 to June 2009. Information was based on data from self-administered questionnaires, physical examination and laboratory results on blood samples. The degree of coronary artery calcification and stenosis was evaluated by a 64 channel multi-detector computed tomography angiography. RESULTS: The prevalence of hypertension(p<0.01) and diabetes mellitus(p=0.02) and waist circumference(p<0.01) was significantly lower in the shipyard office workers than in self employed workers. Proper drinking(p<0.01) was more commmon in shipyard office workers. The rates of coronary artery calcification and stenosis were estimated to be 18.4% and 11.5% respectively for shipyard office workers and were significantly lower than the 26.5% and 21.5% for self employed workers. After adjustment for age, the probability of coronary artery stenosis in shipyard office workers was lower than in self employed workers (OR=0.56, 95% CI=0.35~0.90). CONCLUSIONS: The study results verified the benefits of a health promotion and intervention program and the healthy worker effect for cardiovascular diseases. More specifically, it verified the benefits regarding coronary artery stenosis in large scale industry office workers. This result should encourage the establishment of health promotion programs and the study of occupational epidemiology.

Lombalgia ocupacional / Occupational low back pain

A lombalgia ocupacional apresenta etiologia multifatorial, elevada prevalência e incidência. Caracterizada por quadro de dor de variada duração e intensidade, a dor lombar pode levar à incapacidade laborativa e à invalidez. A lombalgia acarreta sofrimento aos trabalhadores, custos às empresas, aos sistemas previdenciário e assistencial de saúde. Os autores, pela relevância do tema, elaboraram este artigo de revisão bibliográfica dando ênfase ao embasamento teorico-conceitual e à experiência de especialistas.

The occupational low back pain presents multifactorial aetiology, important prevalence and incidence. Characterized by pain of varying duration and intensity, low back pain may lead to disability. Low back pain causes suffering to workers, implies costs to companies, to the social security and health assistance system. Because of the theme's relevance, the authors have elaborated this review of literature with emphasis on a theoretical and conceptual basis, as well as experience of experts.

A study on Statistical Method for Controlling the Effect of Intermediate Events: Application to the Control of the Healthy Worker Effect / 한국역학회지

PURPOSE: The healthy worker effect is an important issue in occupational epidemiology. This study was conducted to propose a new method to test the relation between exposure and mortality in the presence of the healthy worker effect. METHODS: In this study, the healthy worker hire effect was assumed to operate as a confounding variable of health status at the beginning of employment and healthy worker survival effect as a confounding and intermediate variable of employment status. In addition, the proposed method reflects the length bias sampling caused by changing of an employment status. Simulation studies were also carried out to compare the proposed method with Cox's time dependent covariates models . RESULTS: The theoretical development of the healthy worker survival effect is based on the result that an observation with change of an employment status requires that the survival time without intermediate event exceeds the waiting time for the intermediate event. According to our simulation studies, both the proposed method and Cox's time dependent covariates model which includes the change of employment status as time dependent covariates seem to be satisfactory at 5% significance level. However, Cox's time dependent covariates models without or with the change of employment status as time fixed covariate are unsatisfactory. The proposed test is superior in power to tests based on Cox's model. CONCLUSIONS: The healthy worker effect may not be controlled by classical Cox's proportional hazards models. The proposed method performed well in the presence of healthy worker effect in terms of level and power