Which blood values should I have checked to age healthily?

The studies underpinning this answer cover two things: blood tests for the early detection of Alzheimer's disease, and the relationship between gut bacteria and cardiometabolic blood values. They do not provide a complete screening package, but they do offer concrete starting points.

Blood tests that look for Alzheimer's proteins are promising as a first step. However, note that this is intended only for people who already have memory or cognitive complaints and are referred to a specialised memory clinic. A European expert group of 22 specialists recommends a stepwise pathway: first blood tests, then, if necessary, additional imaging or cerebrospinal fluid investigations. This is not a routine check for people without symptoms.

The quality of commercially available Alzheimer's blood tests varies considerably. For screening purposes, minimum standards of at least 90% sensitivity and 75% specificity apply. If you want to use them to replace a brain scan or cerebrospinal fluid test, you need at least 90% specificity. Many tests do not yet meet that threshold, which means false-positive or false-negative results are a real possibility. These tests should therefore only be carried out and interpreted by a specialist.

For cardiometabolic health there is broader evidence. A study in 1,098 healthy participants showed that the composition of gut bacteria was associated with a wide range of blood values: fasting and post-meal blood sugar, cholesterol, triglycerides and inflammatory markers¹. A varied, plant-based dietary pattern was associated with both a more favourable gut microbiome and better outcomes. These are associations, not proof of cause and effect.

In practical terms, the studies support blood sugar, blood lipids and inflammatory markers as meaningful measurements for healthy ageing^2,3,1. Discuss with your GP which package suits your situation. Alzheimer's blood tests belong with the specialist, not in a preventive check-up.