"Months of Time Saved"? What Alzheimer's Drug Numbers Really Mean
Thursday, October 22, 2026
If you or someone you love has been offered lecanemab (Leqembi) or donanemab (Kisunla), you've probably heard the benefits described in a few different ways: the drug "slows decline by about 27%," or it gives people "around six months" before the disease progresses. A group of researchers at University College London (UCL) says families should handle those numbers with care.
What the researchers said. In a Perspective article in the journal Alzheimer's & Dementia: Translational Research & Clinical Interventions, the UCL team looked at how results from Alzheimer's drug trials get translated for patients, families and the public. The trials themselves measure differences on detailed rating scales of memory and daily function, which are hard for non-specialists to interpret. So simpler descriptions have caught on, such as "percent slowing" and "time saved," which estimates how many months of decline the drug delayed. For lecanemab, that estimate has been about 6.6 months. (Source: UCL Faculty of Brain Sciences, October 2026.)
Why it matters. The authors point out that "time saved" figures come from statistical modeling and assumptions about how the disease progresses, not from directly watching people stay independent longer. "They should not be mistaken for directly observed improvements in independence or quality of life," said first author Dr. Jemma Hazan. It's natural for a family to hear "six months" and picture six more months of Mom living on her own or recognizing the grandkids. The trials didn't directly measure that. Senior author Professor Rob Howard said patients and families need an accurate picture of what these drugs can and can't do, especially as they enter everyday practice.
What it does not mean. This isn't a new study showing the drugs don't work. Both drugs did slow decline on the trials' measures compared with placebo. The point is about honest communication: the benefit is real but modest, the drugs carry risks such as brain swelling and bleeding (ARIA), and they require frequent infusions and scans. Whether that trade-off is worth it is a personal decision best made with clear numbers. Our guides to lecanemab and donanemab lay out what the trials directly found, and today we added a new guide, How to Read Health Research News, with a checklist for any headline.
Try this today: ask for the plain numbers
Whenever a doctor or an article describes a treatment's benefit, ask three questions: "What did the study directly measure?" (a test score, a scan, or something in daily life like staying independent), "What happened in the group that got the treatment compared with the group that didn't, in actual numbers?" and "What are the risks and the time involved?" Write the answers down, and bring a family member to the appointment so two people hear them. A good doctor will welcome the questions.
Thanks for reading, and have a good Thursday. We'll see you tomorrow.
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