A lack of sleep may be why poor people are more at risk of heart disease, a new study suggests.
Research shows the most socially deprived could be up to three times more likely to suffer heart attacks and strokes than their well-off counterparts.
READ MORE: The best sleep aids to help you nod off
Little money in the bank was thought to force people to live off ready meals, unable to afford fresh ingredients to make a meal from scratch.
But scientists from the University Centre of General Medicine and Public Health in Lausanne, Switzerland, now believe juggling several jobs, living in a noisy place and coping with financial stress leaves poor people unable to nod off.
A lack of sleep is thought to trigger inflammation, high blood pressure and “furring” of the arteries.
READ MORE: Could 'moon breathing' help you sleep?
Financial instability has been linked to everything from obesity and depression to a higher tendency to smoke.
To learn more about how our bank balance affects our health, the scientists pooled data from eight studies, across four European countries.
The 111,205 participants were asked about both their job and their father’s career, to give an indication of their lifelong socioeconomic status. This was then deemed to be low, middle or high.
The participants were also asked how many hours of sleep they got a night, with medical records revealing any heart issues.
Results suggest “short sleep” - defined as less than six hours - explained 13.4% of the link between occupation and heart disease among the men.
The same was not true for the female participants, which the scientists put down to a “weaker relationship between occupation and sleep duration in women”.
Study author Dusan Petrovic added, however: “Women with low socioeconomic status often combine the physical and psychosocial strain of manual, poorly paid jobs with household responsibilities and stress, which negatively affects sleep and its health-restoring effects”.
Writing in the journal Cardiovascular Research, the scientists explained how chronic sleep deprivation “disrupts the function of several physiological systems”.
This may cause “impairment of immunity and inflammatory processes, altogether leading to an increased cardiovascular risk”.
The scientists are calling for “structural reforms at every level of society” to help people get their recommended seven-to-nine hours of shut eye a night.
“For example, attempting to reduce noise, which is an important source of sleep disturbances, with double-glazed windows, limiting traffic, and not building houses next to airports or highways,” Mr Petrovic said.