White cells in their blood called neutrophils are weakened, sometimes fatally, by the disruption of vital hormones brought on by bereavement, research suggests.
The same effect does not occur in young people, even though grief might hit them hard psychologically.
Scientists believe the findings may explain frequently reported cases of bereavement leading to death months after the loss of a spouse. Usually, it is pneumonia that claims the lives of the broken- hearted.
Study leader, Anna Phillips, reader in behavioural medicine at the University of Birmingham, said: “The neutrophil is a white blood cell. It’s really prolific and what it does is eat and kill rapidly-dividing bacteria, like pneumonia. If your neutrophils are not working properly and you’re exposed to pneumonia, then you’re in trouble.”
The research compared neutrophil responses in 30-strong groups of bereaved younger and older people, as well as non-bereaved individuals.
While neutrophil numbers were not lowered in the older people, their ability to kill bacteria with destructive molecules, called reactive oxygen species, was compromised.
The neutrophils in younger people experiencing grief were not affected the same way.
“We thought this was really interesting and may be one of the key reasons why older people are more susceptible to infection after a bereavement,” said Ms Phillips, speaking at the British Science Festival at the University of Birmingham.
The damaging impact of grief on the immune system was traced to a disruption in the balance of two key hormones that influence the way people respond to stress, cortisol and dehydroepiandrosterone sulphate.
In contrast to their younger counterparts, older individuals in the study were found to have higher levels of cortisol compared with dehydroepiandrosterone sulphate.
Co-researcher Professor Janet Lord, also from the University of Birmingham, said: “Cortisol is known to suppress elements of the immune system during times of high stress, so having an unbalanced ratio of cortisol and dehydroepiandrosterone sulphate is going to affect how able we are to ward off illness.
“But ... it is also incredibly useful — particularly in activating some anti- stress and anti-inflammation pathways — so it’s not as simple as trying to suppress the cortisol in vulnerable people.”
Evidence suggests other elements of the immune system might also be affected by the stress of bereavement, including T-cells and Natural Killer Cells important for fighting viral infections and cancer, the scientists believe. Other studies have shown that people affected by bereavement do not react so well to flu jabs.
The critical age at which losing a loved one threatened to cause serious harm to the immune system appears to be around 65.
Older study participants were 65 and older and the younger participants 28 to 45. The psychological effects of bereavement are known to last a long time — as much as two years, said Ms Phillips.