Short answer: It’s more complicated than the popular phrase suggests. Being mentally active throughout life is genuinely linked to better cognitive performance overall, but at least one major, well-designed longitudinal study found that engaging in stimulating activities didn’t actually slow the rate of cognitive decline as people aged, even though it was linked to a better starting point.
What the Research Actually Shows
A key study directly testing the “use it or lose it” idea was published in the BMJ and described by Alzheimer’s Research UK. Scottish researchers conducted a longitudinal, prospective study specifically examining whether engagement in stimulating brain activities affected the rate of cognitive decline over time. They found people who were more engaged in stimulating activities earlier in life did have better memory and thinking skills as they got older, but crucially, the rate of age-related decline in memory and thinking itself was not measurably affected by that engagement. This is a genuinely important, nuanced distinction: mental activity appears linked to a higher cognitive starting point, but not necessarily to a slower slope of decline from that point onward.
This nuance connects to a broader concept researchers call cognitive reserve. According to Psychology Today, cognitive reserve refers to a kind of back-up capacity that allows some people to maintain relatively preserved cognitive function even in the presence of underlying brain changes or disease. Educational and occupational attainment are strongly linked to greater cognitive reserve, and research also shows that people who regularly engage in cognitively demanding leisure activities may build additional reserve. Importantly, the same source notes that while cognitive training reliably improves performance on the specific trained task, there’s much weaker evidence that this training produces meaningful transfer to broader, more general cognitive performance in everyday life.
There’s also research suggesting the mechanism behind cognitive reserve may be broader than simple “brain exercise.” A study using data from the Cognitive Function and Ageing Study, a large UK study following more than 13,000 older adults, described by ScienceDaily, found that an active cognitive lifestyle was associated with several distinct positive brain changes, including less cerebrovascular disease in men, greater brain weight in women, and greater neuronal density and cortical thickness in both sexes. Lead researcher Michael Valenzuela suggested these findings indicate the protective effect isn’t about specifically strengthening the exact circuits being used, but rather that an active, engaged lifestyle has broader, more general effects on overall brain health.
Experts who work directly in this field add an important refinement to the popular version of “use it or lose it”: novelty and genuine challenge appear to matter more than mere repetition. According to research described by BrainHQ, geriatrician Dr. Manuel Montero-Odasso has explained that the goal of effective brain challenge is pushing yourself to the point where genuine effort is required, to remember things, pay attention, and execute tasks, rather than simply repeating familiar, comfortable activities. He notes specifically that habitual activities like daily crossword puzzles or casual internet browsing may not provide much additional cognitive benefit if you’ve been doing them your whole life; it’s the newness and difficulty of an activity that appears key to building and preserving cognitive reserve.
What This Means in Practice
- Choose genuinely novel, challenging activities over familiar routines. Since novelty appears to matter more than repetition, learning something entirely new is likely more valuable than continuing a long-standing, comfortable mental habit.
- Think broad lifestyle, not narrow brain training. Given evidence pointing to general brain health benefits rather than circuit-specific ones, an overall engaged, active lifestyle likely matters more than any single brain-training app.
- Don’t expect activity alone to fully halt decline. Since the rate of decline itself wasn’t clearly slowed in rigorous research, mental engagement is better understood as building a stronger baseline than as a guaranteed brake on the aging process.
- Start building reserve well before older age. Since cognitive reserve appears to accumulate over a lifetime through education, occupation, and sustained engagement, earlier investment likely pays greater dividends than beginning only once decline is already noticeable.
So “use it or lose it” captures something real, but the more accurate, evidence-based version is closer to “use it and start from a stronger place,” since the clearest benefit shown in rigorous research is a better cognitive baseline, not necessarily a slower rate of decline once aging is already underway.
