A small UK study involving 28 healthy older adults (20 women with average age 70; 8 men with average age 67), has found that those with higher levels of aerobic fitness experienced fewer language failures such as 'tip-of-the-tongue' states.
The association between the frequency of tip-of-the-tongue occurrences (TOTs) and aerobic fitness levels existed even when age and vocabulary size was accounted for. Education level didn't affect TOTs, but only a few of the participants hadn't gone to university, so the study wasn't really in a position to test this out.
However, the larger the vocabulary for older adults, the less likely they were to have TOTs. Older adults also had more TOTs over longer words.
The test involved a 'definition filling task', in which they were asked to name famous people, such as authors, politicians and actors, based on 20 questions about them. They were also given the definitions of 20 'low frequency' and 20 'easy' words and asked whether they knew the word relating to the definition.
Aerobic fitness was assessed by a static bike cycling test.
The study included 27 young adults as a control group, to provide a comparison with older adults' language abilities, confirming that older adults did indeed have more TOTs. The young adults' fitness was not tested. All participants were monolingual.
Segaert et al (2018). Higher physical fitness levels are associated with less language decline in healthy ageing. Scientific Reports. https://www.nature.com/articles/s41598-018-24972-1