Three months of online workouts lifted mood in middle age, but did not sharpen memory

Exercise is often said to be good for the brain, and in particular for the hippocampus, a seahorse-shaped region deep in the brain that is central to memory and shrinks with age. In mice, running makes the hippocampus produce more new nerve cells (neurogenesis). Whether that happens in adult humans is hard to study, because there is no way to count new neurons in a living person’s brain.

The NeuroFit trial, run from King’s College London, looked at midlife, a stage that gets less attention than old age, but when mood often dips and brain changes start.

What they did

The researchers recruited 52 people aged 45 to 65 who did less than 90 minutes of moderate exercise a week and had a body mass index between 20 and 30. Half were randomly assigned to 30-minute live online group classes, three times a week for 12 weeks, mixing aerobic and strength exercises; the other half kept their usual routine. Attendance was high: on average, participants joined 86% of the sessions.

The main outcome was pattern separation: the ability to tell apart very similar memories, such as where you parked today versus yesterday. It is measured with a computer task in which people have to notice that a picture is similar to, but not the same as, one they saw earlier. In animals this skill depends on new neurons in the hippocampus.

The team also measured mood, sleep, general cognition, blood pressure, body fat, a growth factor in the blood (BDNF), and did something unusual: they put participants’ blood serum on human brain stem cells in a dish (a cell line originally from the hippocampus), to see whether exercise changed what the blood “tells” these cells.

What they found

• No change in the memory task. Pattern separation did not improve more in the exercise group than in the control group.
• Better mood. Depressive symptoms, measured with a standard questionnaire, went down more in the exercise group. Nobody in the trial was depressed at the start, so the change was modest.
• More activity, little else. The exercisers became clearly more active. There were no significant differences in general cognition, sleep, blood pressure, BDNF or other blood markers.
• Blood that affects brain cells. Serum from exercisers, taken at the end, slightly reduced the share of dividing stem cells in the dish, without causing cell death or changing how many became neurons. The authors think this may reflect a calmer, more “maintenance” state, but this is an interpretation of a lab model.
• Safe. There were no serious adverse events.

How to read a “negative” result

A trial that doesn’t find what it was looking for is still informative. The authors offer several reasons: three months may be too short (studies that found bigger hippocampi used 6 to 12 months of training), healthy middle-aged people may already do well on the task, leaving little room to improve, and the test was done days after the last workout, while earlier positive studies tested people right after a single session. It was also a small trial, and people responded very differently: some improved, some didn’t, a few got worse.

Why it matters

The take-home message is practical. A short, home-based program that inactive middle-aged people actually stuck to was enough to improve mood within three months. Benefits for memory, if they come, may need more time or more exercise. The authors suggest that effects of exercise arrive in stages: mood first, then changes in the blood, and only later changes in thinking.