Brain training games modestly improve cognitive test scores, but whether this carries over into daily life is unclear. Preventing dementia has not been demonstrated, despite marketing claims. Exercise, social engagement, and blood pressure control are better supported protective factors.
The games work, but exactly what they improve is the real question. An analysis of 52 controlled studies shows that brain-training programmes measurably improve scores on cognitive tests, though the gains are modest. The problem is that laboratory tests are not the same as your memory in everyday life: whether those lab-based gains also mean you find it easier to remember names or switch tasks more quickly at work simply has not been established. A large 2019 Cochrane analysis found only weak evidence for that.
What brain training certainly does not do is prevent dementia. No good studies demonstrate this, despite marketing that sometimes points in that direction. If you enjoy it, there is no reason to stop -- it is completely harmless. But if the goal is long-term brain health, then regular exercise, social engagement and well-managed blood pressure are currently far better supported as protective factors.
Moderate evidence, 2 source(s); the direction is probable but not firmly proven.