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Life course CVD
Working characteristics and cardiovascular disease: are associations confounded by early life risk factors?
  1. C. Thomas,
  2. C. Power
  1. MRC Centre for Epidemiology of Child Health, UCL Institute of Child Health, University College London, London, UK

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    Objectives

    Work characteristics, such as night work, long hours and psychosocial work stress, have been found to be associated with cardiovascular disease (CVD) but the pathways from work to increased CVD risk are unclear. Since numerous early life indicators of CVD risk have been identified, including prenatal, socio-economic, environmental, physical, cognitive and behavioural factors, it is possible that associations seen for work arise through pre-existing CVD risk prior to entering the labour market. To determine whether cross-sectional relationships seen for working characteristics and risk factors for CVD in mid-adult life are confounded by early life risk factors for CVD, the following questions are addressed: (i) are work characteristics associated with CVD risk factors independently of each other? (ii) do work characteristics interact so that combinations of factors carry cumulative risk for CVD? (iii) are associations explained by early life predictors of CVD risk.

    Design

    Birth cohort.

    Setting

    England, Scotland and Wales.

    Participants

    7916 men and women in the 1958 British birth cohort who were in paid employment at 45 y.

    Main Outcome Measures

    Body mass index (BMI), waist circumference (WC), blood pressure (BP), triglycerides, total and high density lipoprotein (HDL) cholesterol, glycosylated haemoglobin (HbA1c), and inflammatory factors: fibrinogen, C-reactive protein (CRP).

    Results

    Night work was associated with adverse levels of most outcomes examined (except BP and total cholesterol). Working ⩾48 h/week was associated with BMI and WC only; low job control with HDL, HbA1c, and inflammatory factors; low demands, rather than high demands, with systolic BP, triglycerides, HDL and inflammatory factors. Several work factor/CVD associations were weakened when mutually adjusted for each other and an interaction between night work and low demands was commonly found. Adjustment for childhood factors up to 16 y explained a substantial proportion of the associations. To illustrate, for BMI, adjustment for a range of childhood factors reduced the associations for night work/low demands (0.78 kg/m2, 95% CI 0.35 to 1.21) and working ⩾48 h/week (0.31 kg/m2, −0.01 to 0.62) by 50% and 22%, respectively. However, BMI at 16 y accounted for 45% of the association between working ⩾48 h/week and BMI at 45 y (adjustment for some childhood factors strengthened the association between work hours and BMI).

    Conclusions

    Initial findings suggest that childhood factors up to the age of 16 y explain a large proportion of the cross-sectional associations seen for work characteristics and risk factors for CVD in mid-adulthood suggesting that associations arise in part from social and health disadvantage originating earlier in life.

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