"When should I start worrying about dementia?" is one of the most common questions people ask — and the best answer is reassuring: the most effective time to act is usually earlier than people expect, and it's never too late to benefit. The 2024 Lancet Commission organizes its 14 modifiable risk factors by life stage precisely because the same factor can matter enormously at one age and very little at another. This guide reorganizes those factors by decade, so you can focus on what carries the most weight for you right now.
One of the most important refinements in the 2024 report was clarifying when each risk factor exerts its greatest influence. Four factors — smoking, depression, physical inactivity, and diabetes — were reclassified from "late life" to "midlife" between the 2020 and 2024 reports, as the evidence clarified that they do their damage earlier than once thought. As one Commission researcher put it: if a factor causes dementia but exerts its influence in midlife, then intervening only in later life will have limited benefit.
That's the practical core of a life-course approach: match your effort to the window where it has the most leverage.
The Commission uses three broad bands — early life (under 18), midlife (18–65), and late life (65+). Most readers of this site fall in midlife or early late-life, so here's a more granular, decade-by-decade view. Tap any stage to expand.
If there's a single takeaway for the 40–65 group that makes up most of this site's readers, it's that midlife is disproportionately important. The vascular and metabolic factors — cholesterol, blood pressure, diabetes, weight — and hearing all sit in this window, and acting on them here has more leverage than acting later. That's not a reason for anxiety; it's a reason to treat a midlife check-up as one of the most useful brain-health appointments you'll ever make.
A common worry: "If dementia runs in my family, does any of this matter?" The evidence is encouraging. The Commission explicitly states that the potential to prevent or delay dementia by addressing modifiable factors applies even in people with high genetic risk.
Whatever your decade, the same five daily-habit domains carry the load — the emphasis just shifts with age. Start with whichever is most relevant to your stage and your personal risk profile.
The same 14 risk factors don't carry equal weight at every age, and that's good news: it means you can focus. In your 40s and 50s, the vascular, metabolic, and sensory factors offer the most leverage — this is the window to build the foundation. In your 60s and beyond, social connection, physical activity, and protecting your hearing and vision come to the fore. And at every stage, the Commission's evidence is clear that acting helps — even with a family history, even later in life. The best time to start was earlier; the second-best time is now.
Medical disclaimer: This content is for educational purposes and is not medical advice. Consult a healthcare professional before making changes to your health routine.
Last reviewed: June 2026