Putative risk factors accelerating mild cognitive decline and dementia were correlated with repeated measures of cerebral atrophy, CT, densitometry, perfusions, and cognitive testing among neurologically and cognitively normative aging volunteers. A total of 224 normative subjects at increased risk for cognitive decline were admitted to the study. Mean entry age was 59.5 +/- 15.8 years. Mean follow-up is 5.8 +/- 3.3 years. At follow-up, 22 developed mild cognitive impairment (41 CCSE >/= -3), 19 became demented-8 with Vascular type (VAD), 11 with Alzheimer's type (DAT)-and 183 remain cognitively unchanged. Cerebral atrophy, tissue densities, and perfusions were measured by Xe-CT. After age 60, cerebral atrophy, ventricular enlargement, and polio- and leuko-araiosis geometrically increased as perfusions declined. Risk factors accelerating perfusional decline, cerebral atrophy, polio-araiosis, and leuko-araiosis were: transient ischemic attacks (TIAs), hypertension, smoking, hyperlipidemia, and male gender. At age 71.5 +/- 11.9, mild cognitive impairment began accelerated by TIAs, hypertension and heart disease. Leuko-araiosis began before cognitive decline. TIAs, hypertension, and hyperlipidemia correlated with VAD. Excessive cortical perfusional decrease, gray and white matter hypodensities, and cerebral atrophy correlate with cognitive decline.