A study has recommended that common over-the-counter medicines for colds and flus should be avoided by older people after a link was found between the medicines and a reduction in brain function.
According to scientists at Indiana University School of Medicine the study found that two of the key ingredients promethazine and diphenhydramine found in these medicines were causing reduced brain function and smaller brains.
The medicines affected include cold and flu tablets, medicines for hay fever and even anti-heartburn pills.
The study found that the two drugs were blocking the chemical acetylcholine which is used in the transmission of electrical signals within the brain.
While the study doesn't cite any major concerns for younger patients it does recommend that for older patients, these drugs have been linked to an increased risk of dementia.
‘Given all the research evidence, physicians might want to consider alternatives to anticholinergic medications if available when working with their older patients.' said Dr Shannon Risacher at IUSM.
While the side-effects of these drugs has been known for some time, this study is the first to get conclusive evidence through the use of MRI scans.
The study involved over 451 participants, 60 of which were taking a relatively high dose of medication containing both drugs.
To then test the theory the study asked the participants to engage in a range of cognitive tests which looked at memory retention.
What they found was that out of the 451, those taking drugs which contained promethazine and diphenhydramine performed worse than older adults who had not taken the drugs.
The study isn't perfect though, with a mean age of over 70 it doesn't take into account the long-standing effects it could have on younger patients.
Nor does the study take into account that many of these medicines are designed for continued use, with most cold and flu tablets being used infrequently as and when required.