“Too much phone time will give you dementia.” The idea even has a name now, digital dementia, and plenty of older adults worry about it.
So what does the data on older people actually show?
The largest summary so far is a 2025 meta-analysis by Benge and Scullin in Nature Human Behaviour. It pooled 57 studies covering 411,430 people, with a mean age of 68.7 and follow-up of 1 to 18 years (6.2 on average). The result runs opposite to the worry.
What the numbers say
People who used digital technology such as computers, smartphones and the internet had odds of cognitive impairment of 0.42 (95% CI 0.35 to 0.52). In the longitudinal studies, the hazard ratio for the rate of cognitive decline was 0.74 (0.66 to 0.84). The authors report the results held after adjusting for demographics, socioeconomic status and health.
Two competing ideas
The paper tested two opposing hypotheses. One is the “digital dementia” idea, that devices erode attention and memory. The other is “technological reserve,” the idea that staying fluent with new tools builds up mental reserve. The pooled data leaned toward the second. But only as an association. These were not randomized trials.
It does not mean phones protect your brain
Every study in the analysis was observational, and the authors say plainly that causation can’t be established. Reverse causation is a live possibility: people whose thinking is still sharp are the ones who can handle a smartphone in the first place.
So what the study knocked down is the simple claim that technology causes dementia. It did not prove that using a phone prevents it.
How many older Japanese are online?
Japan’s Ministry of Internal Affairs and Communications, in its 2024 Communications Usage Trend Survey (published May 30, 2025), found internet use at 65.9% among people 70 to 79 and 48.1% among those 80 and over. Every age band from 13 to 69 was above 90%. Smartphone ownership across the whole population was 80.5%.
About half of people in their 80s are already online. The other half aren’t.
Start with one small use
The meta-analysis didn’t test any particular app. It looked at technology use in general, so the first step can be anything: a video call with family, a map app for getting around, sorting photos, checking the weather. Once you have one reason to pick the phone up, the buttons start to make sense.
Connection matters too. A 2015 meta-analysis by Holt-Lunstad and colleagues in Perspectives on Psychological Science reported 29% higher mortality risk with social isolation, 26% with loneliness and 32% with living alone. That evidence is mostly observational as well, and people who are already unwell tend to become isolated, so the arrow can point the other way. Still, being able to see the face of a relative who lives far away is a practical way to ease isolation.
Learning to use a device takes effort, and that effort is itself a workout for the brain. That part is my own opinion; the paper didn’t test the mechanism.
One caution. If screen time starts eating into your sleep or your walking, that’s a bad trade. If you’re worried about either, talk to your family doctor.
Next Thursday, a different kind of tool.
References
- Benge JF, Scullin MK. A meta-analysis of technology use and cognitive aging. Nature Human Behaviour. 2025;9(7):1405-1419.
- Holt-Lunstad J, Smith TB, Baker M, Harris T, Stephenson D. Loneliness and social isolation as risk factors for mortality: a meta-analytic review. Perspectives on Psychological Science. 2015;10(2):227-237.
- Ministry of Internal Affairs and Communications (Japan). 2024 Communications Usage Trend Survey (published May 30, 2025).
Related book: Walking to 110: Wisdom from the World’s Longest-Lived Nation (Kindle)