High-dose flu shot may lower seniors' risk of dementia by 55%

A study of nearly 200,000 Americans age 65 and older found that receiving a high-dose influenza vaccine was associated with about a 55% lower risk of Alzheimer's dementia over roughly two years, with stronger and more consistent associations reported in women. Researchers noted limitations including possible healthy-user bias and missing data on mortality and socioeconomic factors.

A new study reports that older Americans who received a high-dose influenza vaccine were less likely to develop Alzheimer's dementia than those who received the standard vaccine or skipped vaccination. The analysis included nearly 200,000 adults aged 65 and older and found about a 55% lower risk over roughly two years. Women appeared to gain the most consistent and longer-lasting benefits, though researchers do not yet know why. The CDC has recommended a high-dose flu option for adults 65 and older since 2022, and the high-dose formulation is reported to be about four times stronger than the standard shot. The study's authors and others acknowledged several limitations in their analysis. Key details: - The study analyzed nearly 200,000 adults aged 65 and older and reported an association of about a 55% lower risk of Alzheimer's dementia over roughly two years for recipients of the high-dose influenza vaccine. - Both men and women showed reductions in risk, with women reportedly experiencing longer-lasting and more consistent benefits; the cause of the sex difference was not determined. - The CDC recommended a high-dose influenza vaccine for adults 65 and older beginning in 2022; the high-dose option is described as about four times the antigen level of the standard vaccine. - Earlier research from UTHealth Houston found that seniors who received the standard flu shot were about 40% less likely to develop Alzheimer's over a four-year period compared with those who skipped vaccination. - Study limitations included possible healthy-user bias and missing information on mortality and socioeconomic factors, which the authors noted could affect interpretation. Summary: The reported association suggests the high-dose influenza vaccine was linked with a notably lower incidence of Alzheimer's dementia among older adults in the study sample, especially among women. Researchers are exploring possible mechanisms, including effects on immune response and reductions in systemic and brain inflammation. The analysis had gaps and potential biases that limit causal conclusions. Undetermined at this time.