Academic journal article Scandinavian Journal of Work, Environment & Health

The Association between Long Working Hours and Health: A Systematic Review of Epidemiological Evidence

Academic journal article Scandinavian Journal of Work, Environment & Health

The Association between Long Working Hours and Health: A Systematic Review of Epidemiological Evidence

Article excerpt

In Japan, long working hours is an issue that needs to be addressed promptly for the sake of workers' health. Karoshi (sudden death caused by cardiovascular or cere- brovascular disease due to overwork) and karojisatsu (suicide due to overwork) may also be related to work- ing long hours. According to data from the Japanese Ministry of Health, Labor, and Welfare, the number of workers suffering from cardiovascular disease, cere- brovascular disease, and mental disorders due to work has increased by about threefold in the last decade (1, 2). Long working hours are common in many countries. According to statistics from the Organisation for Eco- nomic Cooperation and Development (OECD) on annual average working hours (3), Korea had the longest work- ing hours between 1980-2007. However, in 2008, Korea dropped to second place behind Mexico. Similar to Japan, karoshi became recognized as a problem in Korea from the early 1990s (4) and consequently the number of working hours may deliberately have been reduced. An International Labor Organization (ILO) report (5) found that the proportion of workers working ?49 or 50 hours/week in 2004-2005 was 49.5% in Korea, 23.6% in New Zealand, 20.4% in Australia, 18.1% in the US, and 14.7% in France. It also estimated that 22.0% of workers globally were working >48 hours/week.

Based on such data, many studies have examined the association between long working hours and health. Various outcomes such as all-cause mortality (6), dis- ease (especially cardiovascular disease) (6, 7), biologi- cal indices [heart rate variability, blood pressure (BP), respiratory sinus arrhythmia, etc] (8-10), sleep (8, 9), depressive state (11), alcohol use (12), body mass index (8-10), fatigue (8-10), and general health status (13) have been investigated and positive, negative, or no association reported. The influence of long working hours on human health remains controversial, and we suggest that inconsistencies in the results are attributable to several factors such as the definition of long working hours, characteristics of participants, inclusion of shift work, measurement of outcomes, and potential covari- ates. In this systematic review, we mainly focused on excluding differences in the definition of long working hours and the influence of shift work.

Long working hours is recognized as working for a length of time which exceeds standard working hours. However, the definition of standard working hours may differ from country to country. For example, standard working hours are 35, 37, and 40 hours/week in France (14), Denmark (15) and the US (14), respectively. In Japan, the Labor Standards Law defines the maximum working time as 40 hours/week. The ILO Convention "Hours of Work to 40 a Week (C047)" was adopted in 1935 (16), but most countries, including Japan, have not ratified it. Under the European Union's Working Time Directive (2003/88/EC), worktime, including overtime, was limited to 48 hours/week. The difference in standard working hours might affect the definition of long work- ing hours in studies examining the association between long working hours and health. Consequently, this might influence the results of some studies. Therefore, we rec- ognize that standard working hours are around 40 hours/ week or 8 hours/day, and long working hours are defined as working longer than this. Moreover, in a study which investigates the association between long working hours and health, we believe that the results would be clearer and easier to understand when standard working time is used as the reference category in the analysis.

There are many types of shift work schedules, for example, night, irregular, and rotating shifts. Many studies have elucidated the association between shift work and health (17-22), and shift work is considered detrimental to health. Shift work has been associated with increased risk for myocardial infarction, coronary events, ischemic stroke (17), gastrointestinal symp- toms, gastric ulcers (18), and metabolic syndrome (19). …

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