Our episodic memory – the ability to recall past events and experiences – is known to decline as we age. Exactly how and why has remained something of a mystery, and a recent study goes some way towards solving it.

Researchers led by a team from the University of Oslo in Norway wanted to see whether this memory loss affects everyone equally, or if it might be driven by individual risk factors, such as the APOE ε4 gene linked to Alzheimer’s disease.

The scale of their analysis is impressive. The scientists combined data from 3,737 cognitively healthy participants, tracked over several years, including 10,343 MRI scans and 13,460 memory assessments, from multiple long-running studies.