Washington: Social isolation can cause sleep loss and age-related diseases such as Alzheimer’s, say scientists, including one of Indian origin, who have broken new ground relating to the connection of loneliness and ill health.

Researchers at the University of Pennsylvania observed that in the fruit fly Drosophila melanogaster, social isolation leads to sleep loss, which in turn leads to cellular stress and the activation of a defence mechanism called the unfolded protein response (UPR). Although its short-term activation helps protect cells from stress, chronic activation can harm cells. Long-term, harmful activation of the UPR is suspected as a contributor to the ageing process and to specific age-related diseases such as Alzheimer’s and diabetes.

“A lot of elderly people live alone, and so we suspect that stresses from the combination of ageing and social isolation creates a double-whammy at the cellular and molecular level," said Nirinjini Naidoo, a research associate at University of Pennsylvania. “If you have an age-related disruption of the UPR response, compounded by sleep disturbances, and then you add social isolation, that may be a very unhealthy cocktail," Naidoo said. While evaluating the effects of ageing on the UPR in fruit flies, researchers noticed that molecular markers of UPR activation were at higher levels in flies kept singly in vials, compared to same-aged flies kept in groups.

“Ultimately, we realized that keeping animals isolated induces a cellular stress response and a higher level of UPR activation," Naidoo said. UPR is supposed to protect against this cellular catastrophe. However, when it fails to work efficiently to restore proper protein-folding conditions, and stays activated, it can trigger harmful inflammation, suppress normal, healthy cellular activity, and ultimately force the death of the cell.

Scientists have found evidence that this inefficient, chronic response becomes more likely with ageing. The findings were published in the journal Sleep.