Researchers found that biological stress indicators for mums working 37 or more hours a week while bringing up a child were 18% higher than for women without children.
Biological markers for women bringing up two children while working, including stress related hormones and blood pressure, were 40% higher.
But flexitime or working from home had no effect on stress levels, according to the study published in the journal Sociology.
Employers often introduce flexible arrangements to help employees balance work and home commitments. But the research found that working fewer hours was the only thing that reduced participants’ biomarkers.
Chronic stress levels for women with two children working reduced hours through part-time work, job share and term-time flexible working arrangements were 37% lower than those working in jobs where flexible work was not available.
Men’s chronic stress markers were also lower if they worked reduced hours, with the effect being about the same as for women.
Researchers from the universities of Manchester and Essex analysed data from 6,025 participants in the UK Household Longitudinal Survey. This collects information on working life and measures of stress response, including hormone levels and blood pressure.
Raw data was adjusted to rule out other influences, such as the women’s ages, ethnicity, education, occupation and income, so that the influence of working hours and family conditions could be studied in isolation.
Eleven markers in five biological systems were used to measure stress:
- the neuroendocrine system
- the metabolic system
- the immune and inflammatory systems
- the cardiovascular system and
- the anthropometric system.
The measurements were taken by nurses as part of the UK Household Longitudinal Survey.
These markers measure the overall “allostatic load”, or the long-term stress a person experiences. The allostatic load model is therefore a measure of cumulative wear and tear in a number of physiological systems. It has been consistently associated with poor health and greater risk of death.