The dementia wave from lead is just starting.

The cardiovascular wave from lead is receding. The dementia wave is not.

The same peak-exposure birth cohort that drove cardiovascular mortality in their middle age is now aging into the dementia incidence window. The dementia death curve has not crested. It is still climbing.

The 1945–1965 cohort is the wave

Lead crosses the blood-brain barrier. It disrupts neuron signaling. It accelerates the protein-misfolding cascades seen in Alzheimer's. A 2023 cohort study in JAMA Network Open found higher cumulative lead exposure tracks with accelerated cognitive decline, independent of vascular risk factors.

The kids who took in the most lead from 1950s and 1960s leaded exhaust are now 65 to 80. That is the dementia incidence window.

The IQ panel is the long shadow

Bottom-right. A bell curve of mean IQ points lost per person, by birth year. The 1973 cohort was hit hardest, with about 6.4 IQ points lost per person on average. Multiply that across the entire post-WWII population and you get roughly 1.1 billion IQ points lost in total.

IQ is a blunt measure. But 6.4 points off the population mean shifts the entire distribution. Fewer people two standard deviations above. More people two standard deviations below. Generations of cognitive ceiling lowered, quietly.

The two waves panel is the part to sit with

Bottom-left. The red wave (cardiovascular deaths) is past its peak. The purple wave (dementia deaths) is still rising. Same generation. Same childhood exposure. Two different tissues, two different latencies.