New Delhi, Oct 22 : Some antihistamines -- anti-allergy drugs -- have the potential to raise dementia risk in elderly, claimed a new study on Wednesday.

Dementias are estimated to affect more than 57.4 million people worldwide -- a number that is expected to almost triple to 152.8 million cases by 2050.

Early signs include memory loss, difficulty finding words, confusion, and changes in mood and behaviour.

An analysis in the Journal of the American Geriatrics Society revealed that older inpatients admitted by physicians who prescribe higher amounts of first-generation antihistamines face an elevated risk of delirium (a sudden, severe state of confusion) while in the hospital.

'First-generation antihistamines, such as diphenhydramine, are among the leading causes of medication-related harms in older adults, and although these medications are indicated for histamine-related conditions such as hives and anaphylaxis, they may be prescribed inappropriately,' said the researchers from the University of Toronto.

The team analysed data on 328,140 patients aged 65 years and older who were admitted by 755 attending physicians to 17 hospitals in Ontario, Canada, in 2015-2022.

They found that the overall prevalence of delirium was 34.8 per cent. Patients admitted to physicians who more commonly prescribed first-generation antihistamines had 41 per cent increased odds of experiencing delirium compared with patients admitted to physicians who rarely prescribed first-generation antihistamines.

Delirium, which occurs in up to 50 per cent of hospitalised older adults, has been associated with major adverse outcomes in older adults, including increased mortality and long-term cognitive impairment.

"We hope our study raises awareness among hospitalists that sedating antihistamines can be harmful, and should be prescribed with caution," said corresponding author Aaron M. Drucker, from the University of Toronto and Women's College Hospital.

First-generation antihistamines are indicated for histamine-mediated conditions such as urticaria and anaphylaxis, but may be prescribed inappropriately for non-histamine-mediated pruritic conditions such as type-IV hypersensitivity drug eruptions or non-specific pruritus.

Even when prescribed for histamine-mediated conditions, first-generation antihistamines do not have efficacy benefits over non-sedating antihistamines, which are associated with fewer harms, the team said.

/IANS