Dementia risk detectable up to 25 years before symptoms, study suggests

Researchers analyzed blood samples from 2,766 older women and found that higher levels of the phosphorylated tau 217 (p-tau217) biomarker were linked with greater risk of future mild cognitive impairment and dementia over up to 25 years of follow-up.

Researchers at the University of California San Diego report that a blood test measuring phosphorylated tau 217 (p-tau217) was linked to long-term dementia risk in older women. The team analyzed stored blood samples from 2,766 participants in the Women's Health Initiative Memory Study who were 65 to 79 years old and showed no cognitive decline at baseline. Participants were followed for up to 25 years to track development of mild cognitive impairment and dementia. The findings were published in JAMA Network Open and noted differences by age, APOE ε4 status, and hormone therapy assignment. Key findings: - Study analyzed 2,766 women aged 65–79 with no initial cognitive decline. - Higher plasma p-tau217 levels at baseline were strongly associated with later mild cognitive impairment and dementia. - Associations were stronger in women over 70 and in those with the APOE ε4 gene. - p-tau217 predicted dementia more strongly among participants randomized to estrogen and progestin therapy versus placebo. - Authors noted blood-based biomarkers are less invasive than brain imaging or spinal fluid tests but are still under study and not recommended for routine screening in people without symptoms. - The study examined only older women and evaluated overall dementia outcomes rather than specific subtypes. Summary: The study suggests p-tau217 measured in blood could identify higher dementia risk decades before symptoms in older women, which could inform research and targeted monitoring. Further research is required to confirm findings, to examine interactions with genetics and hormone therapy, and to determine whether results apply to men and younger populations.