The olfactory bulb (OB) of mice contains neural stem cells (NSCs) that can differentiate into various interneuron subtypes. Here, transcriptomic analysis showed that quiescent NSCs (qNSCs) in young and old mice exhibit similar transcriptional profiles, but that the proportion of qNSCs increases with age. As qNSCs are more resistant to injury-induced activation, they are less able to promote repair in aged brains. The increased proportion of qNSCs with ageing seems to result from locally secreted inflammatory mediators and increased expression of antagonists of WNT signalling.