Individual employment histories and subsequent cause specific hospital admissions and mortality: a prospective study of a cohort of male and female workers with 21 years follow up

Does persistent precarious employment affect health outcomes among working age adults? A systematic review and meta-analysis

OBJECTIVE

To evaluate the impact of persistent precarious employment (lasting 12+ months) on the health of working age adults, compared with more stable employment. Persistent precarity reflects a shift towards less secure forms of employment and may be particularly important for health.

METHODS

Nine databases were systematically searched to identify quantitative studies that assessed the relationship between persistent precarious employment and health outcomes. Risk of bias (RoB) was assessed using an adaptation of the Effective Public Health Practice Project tool. Narrative synthesis and random effects meta-analysis were conducted. Certainty of evidence was assessed using the Grades of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Of 12 940 records screened, 50 studies met the inclusion criteria and 29 were included in meta-analyses. RoB was generally high (n=18). The most reported outcome domain was mental health; with evidence also reported relating to general health, physical health,and health behaviours. Of GRADE assessed outcomes, persistent precarious employment was associated with increased risk of poor self-rated health (OR 1.53, 95% CI 1.09 to 2.14, I2=80%) and mental health symptoms (OR 1.44, 95% CI 1.23 to 1.70, I2=65%). The association with all-cause mortality was imprecisely estimated (OR 1.10, 5% CI 0.91 to 1.33, I2=73%). There was very low GRADE certainty across all outcomes.

CONCLUSIONS

Persistent precarious employment is associated with poorer health, particularly for outcomes with short time lags, though associations are small and causality is highly uncertain. Further research using more robust methods is needed but given potential health harms of persistent precarious employment, exploration of precautionary labour regulations and employment policies is warranted.

After 50 years and 200 papers, what can the Midspan cohort studies tell us about our mortality?

OBJECTIVE

To distil the main findings from published papers on mortality in three cohorts involving over 27,000 adults, recruited in Scotland between 1965 and 1976 and followed up ever since.

METHOD

We read and summarized 48 peer-reviewed papers about all-cause and cause-specific mortality in these cohorts, published between 1978 and 2013.

RESULTS

Mortality rates were substantially higher among cigarette smokers in all social classes and both genders. Exposure to second-hand smoke was also damaging. Exposure to higher levels of black smoke pollution was associated with higher mortality. After smoking, diminished lung function was the risk factor most strongly related to higher mortality, even among never-smokers. On average, female mortality rates were much lower than male but the same risk factors were predictors of mortality. Mortality rates were highest among men whose paternal, own first and most recent jobs were manual. Specific causes of death were associated with different life stages. Upward and downward social mobility conferred intermediate mortality rates. Low childhood cognitive ability was strongly associated with low social class in adulthood and higher mortality before age 65 years. There was no evidence that daily stress contributed to higher mortality among people in lower social positions. Men in manual occupations with fathers in manual occupations, who smoked and drank >14 units of alcohol a week had cardiovascular disease mortality rates 4.5 times higher than non-manual men with non-manual fathers, who neither smoked nor drank >14 units. Men who were obese and drank >14 units of alcohol per day had a mortality rate due to liver disease 19 times that of normal or underweight non-drinkers. Among women who never smoked, mortality rates were highest in severely obese women in the lowest occupational classes.

CONCLUSION

These studies highlight the cumulative effect of adverse exposures throughout life, the complex interplay between social circumstances, culture and individual capabilities, and the damaging effects of smoking, air pollution, alcohol and obesity.

Resolving mechanisms of toxicity while pursuing ecotoxicological relevance?

In this age of modern biology, aquatic toxicological research has pursued mechanisms of action of toxicants. This has provided potential tools for ecotoxicologic investigations. However, problems of biocomplexity and issues at higher levels of biological organization remain a challenge. In the 1980s and 1990s and continuing to a lesser extent today, organisms residing in highly contaminated field sites or exposed in the laboratory to calibrated concentrations of individual compounds were carefully analyzed for their responses to priority pollutants. Correlation of biochemical and structural analyses in cultured cells and tissues, as well as the in vivo exposures led to the production and application of biomarkers of exposure and effect and to our awareness of genotoxicity and its chronic manifestations, such as neoplasms, in wild fishes. To gain acceptance of these findings in the greater environmental toxicology community, "validation of the model" versus other, better-established often rodent models, was necessary and became a major focus. Resultant biomarkers were applied to heavily contaminated and reference field sites as part of effects assessment and with investigations following large-scale disasters such as oil spills or industrial accidents. Over the past 15 years, in the laboratory, small aquarium fish models such as medaka (Oryzias latipes), zebrafish (Danio rerio), platyfish (Xiphophorus species), fathead minnow (Pimephales promelas), and sheepshead minnow (Cyprinodon variegatus) were increasingly used establishing mechanisms of toxicants. Today, the same organisms provide reliable information at higher levels of biological organization relevant to ecotoxicology. We review studies resolving mechanisms of toxicity and discuss ways to address biocomplexity, mixtures of contaminants, and the need to relate individual level responses to populations and communities.

The Scottish mental survey 1932 linked to the Midspan studies: a prospective investigation of childhood intelligence and future health

The Scottish mental survey of 1932 (SMS1932) recorded mental ability test scores for nearly all children born in 1921 and at school in Scotland on 1 June 1932. The Collaborative and Renfrew/Paisley studies, two of the Midspan studies, obtained health and social data by questionnaire and a physical examination in the 1970s. Some Midspan participants were born in 1921 and may also have taken part in the SMS1932, so there was a possibility that their mental ability data from childhood would be available. The 1921 born Midspan participants were matched with the computerized SMS1932 database, and in total, 1032 of 1251 people (82.5%) were matched successfully. Of those matched, 938 (90.9%) had a mental ability test score recorded. The mean score of the matched sample was 37.2 (standard deviation (SD) 13.9) out of a possible score of 76. The mean (SD) for the boys and girls was 38.3 (14.2) and 35.7 (13.9), respectively. This compared with 38.6 (15.7) and 37.2 (14.3) for boys and girls in all of Scotland. Graded relationships were found between mental ability in childhood, and social class and deprivation category of residence in adulthood. Being in a higher social class or in a more affluent deprivation category was associated with higher childhood mental ability scores, and the scores reduced with increasing deprivation. Future plans for the matched data include examining associations between childhood mental ability and other childhood and adult risk factors for disease in adulthood, and modelling childhood mental ability, alongside other factors available in the Midspan database, as a risk factor for specific illnesses, admission to hospital and mortality.

Frequent job change and associated health

The contemporary labour market is widely regarded as having become more "flexible". It is proposed that such flexibility is a characteristic of employment histories which will have effects on psychosocial status, health-related behaviour, and physical health. Recent increases in flexibility are unlikely to have accumulated over sufficient portions of individual employment histories for any effect on health to be apparent, but a "preview" of these effects may be gained from study of older cohorts. This cross-sectional study is based on data collected in the early 1970s from 5399 men and 945 women in paid work, recruited from 27 workplaces in the west of Scotland. A flexible employment history was defined as one encompassing a large number of changes between jobs. Perceived psychological stress, health behaviour (cigarette smoking, alcohol consumption, physical exercise), physiology (diastolic blood pressure, body mass index, forced expiratory volume, plasma cholesterol concentration) and current health (angina, myocardial ischaemia) were assessed. Those individuals who reported having experienced frequent job change were more likely to smoke, consume greater amounts of alcohol, and perhaps to exercise less. Similar findings were observed in both males and females, and for different age and socio-economic groups. We found no suggestion that this association was due to higher levels of psychosocial stress, and the expected consequences for health were not observed. Interpretation of these findings is not straightforward due to an uncertain direction of causation, and a possible selection bias. However, the observed relationship between frequent job changing and a higher incidence of health risk behaviours, in the absence of a relationship with poorer health, invites further research.