Socioeconomic Factors, Work and Chronic Diseases

The WHO Global status report on noncommunicable diseases 2010 showed that NCDs are the biggest cause of death worldwide. More than 36 million people died from NCDs in 2008, mainly cardiovascular diseases (48%), cancers (21%), chronic respiratory diseases (12%) and diabetes (3%). More than 9 million of these deaths occurred before the age of 60 and could have largely been prevented. Socioeconomic disadvantage is a major contributing factor to health differences. Differences in socioeconomic status have been consistently associated with chronic disease incidence and mortality across multiple populations, with low socioeconomic groups showing lower survival and higher incidence in many populations in developed countries. Stress at work is a major public health issue in modern societies, potentially contributing to a range of health-related outcomes, such as reduced quality of life, disability, cardio- and cerebro-vascular diseases, and depression. Given the link between social factors, exposure to work-related risk factors and chronic disease, it is likely that work may have a role in generating health inequalities.

Coronary heart disease and stroke (CVD) are the leading noncommunicable diseases, measured by global mortality and morbidity, and are projected to remain so for the foreseeable future. They develop slowly through life course due to atherosclerosis of blood vessels. The conventional risk factors of CVD are tobacco use, raised blood pressure, raised blood cholesterol and diabetes mellitus. Many other factors increase the risk of CVD, including unhealthy diet, physical inactivity, obesity, age, male sex, family history of early onset of coronary heart disease and insulin resistance. Other suggested determinants include socioeconomic factors, housing and living conditions, employment and employment security, psychosocial stress, and health care services.

Socioeconomic factors can influence the risk of chronic diseases differentially along the life course. In childhood, poor living conditions and the parents’ social class have a strong impact on adulthood health status. In middle age, conventional risk factors increase the risk of CVD. These may be affected by more distal risk factors, such as work and material conditions. In later life access to medical care, and social and family support may have a strong impact on cardiovascular health.

Adult socioeconomic factors (as indicated by, for example, levels of occupational status, income, and neighbourhood characteristics) affects CVD outcomes by association with the cardiovascular risk factors and the overall cardiovascular outcome measures. Cardiovascular risk factors tend to cluster with lower socioeconomic status and include diabetes, smoking, raised blood pressure, dislipidaemia, central obesity and inflammatory markers.

Only part of the variation in chronic disease incidence across the social gradient is explained by established risk factors. Stress at work is a major public health issue in modern societies, potentially contributing to a range of health-related outcomes, such as reduced quality of life, disability, cardio- and cerebro-vascular diseases, and depression. According to recent European Union estimates, stress is cited as a factor in half of all lost working days and thus represents a substantial cost in terms of human distress and impaired economic performance. There is an inverse association between occupational position and work stress, showing higher exposure in lower grades. There is also an association between work stress and proximal risk factors for chronic diseases. For example, stress might contribute to an unhealthy life style, such as physical inactivity, unfavorable diet, higher smoking intensity and reduced likelihood to quit smoking as well as increased alcohol consumption which in turn could induce weight gain. To date, however, the empirical evidence for an association between work stress and health risk behaviours has been inconsistent, revealing positive (more stress, more risk behaviours), null, and inverse (more stress, less risk behaviours) findings. Small sample sizes in most of these studies may have contributed to the mixed results. Currently, a more precise characterisation of the association between work stress and behavioural health risks is emerging from pooled data of more than 13 independent cohort studies (The Individual-participant-data meta-analysis in working populations (IPD-Work) consortium).

Observational data suggest an excess risk for chronic diseases, including CHD and common mental disorders, in employees with work stress. This is supported by natural experiments which have shown that stressful changes at work increase the risk of major chronic diseases. Since the recessions that hit most industrialised countries during the 1990s evidence has accumulated of health risks to the survivors of corporate downsizing. One of the first studies in the field was conducted among municipal employees of town of Raisio, in Finland. The Raisio study found that the risk of health problems was at least two times greater after major downsizing than after no downsizing. Half of excess risk after downsizing was attributable to an elevated level of work stress as indicated by reduced job control and organisational justice and increased work demands and job insecurity. Adverse effects on the health of survivors of downsizing have since been demonstrated in a number of other studies. For example, findings from the Finnish 10-Town study suggest that downsizing is associated not only with an increased risk of heightened morbidity but also with early exit from fork force through disability pensioning and premature death from cardiovascular disease.

Although further research is needed to confirm that a reduction of work stress will lead to a reduction in the disease risk, this possibility is supported by a natural experiment on the health effects of the removal of all work-related stress. Recently, it has been shown that the burden of ill-health, in terms of perceived health problems, fatigue and depression, is substantially relieved by retirement for all groups of workers but those with ideal working conditions in societies with good social security. Overall, perceived health problems increase with age before as well as after retirement. However, between the year before retirement and the year after, there was a steep decrease in health problems. This retirement-related improvement has been found in both men and women, and across occupational grades. A poor work environment and health complaints before retirement were associated with a steeper yearly increase in the prevalence of health problems while still in work, and a greater retirement-related improvement; however, people with a combination of high occupational grade, low demands, and high satisfaction at work showed no such retirement-related improvement. These studies suggest that work stress puts an extra burden on health, but that the effects of this burden are reversible. Unsurprisingly, no break in the trend around retirement has been observed in relation to the cumulative prevalence of chronic diseases.

The Whitehall II study is one of the few studies which have been able to move from demonstrating associations to causality. Findings from that study indicate that around one third of the effect of work stress on CHD can be explained by the effect of work stress on health behaviours (low physical activity and poor diet in particular) and the metabolic syndrome. However, while job strain has been shown to contribute to cardiovascular disease and mortality in white-collar occupations, the contribution to those in more physical jobs is less obvious, although strain does appear to increase risk for injury and depression.

Weighing the current evidence, it would appear that occupation—or at least some of its component elements—contribute causally to the health gradients. As the global economy shifts, the implications of stressful changes at work (for example, nonstandard work, changing shifts and work insecurity) to SES gradients in health will be an urgent question. So far we do not know how much of the variation in chronic disease incidence across the social gradient could be explained by work stress.