The neurodegenerative changes leading to clinical Alzheimer's disease may begin in middle age. If risk factors could be identified, intervention to prevent or delay the onset of dementia could perhaps be developed. Alzheimer's disease has been linked to vascular disease, particularly to raised blood pressure and cholesterol levels. Kivipelto and colleagues used large longitudinal population studies conducted in Finland to study the association between elevated blood pressure and cholesterol levels during middle age and subsequent development of Alzheimer's disease.
Data were abstracted from four large population studies conducted between 1972 and 1987. Participants who were still alive and living in the same region were re-examined in 1998. Those between 65 and 79 years of age were screened for dementia based on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition. The mean age at original examination was 50.4 and at re-examination was 71.3. The diagnosis of Alzheimer's disease was based on criteria of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer Disease and Related Disorder Association. Of the 1,449 eligible participants, 57 (4 percent) were diagnosed with dementia, and 48 of those with probable or possible Alzheimer's disease. All had cerebral atrophy, but none had intracranial vascular pathology on magnetic resonance imaging examination. Diagnosis of Alzheimer's disease was significantly related to raised systolic blood pressure during middle age, and the association persisted after adjusting for age, body mass index, education, smoking status, and alcohol use. Diastolic blood pressure presented no significant increased risk. High systolic blood pressure and high serum cholesterol levels also showed significant associations with development of Alzheimer's disease and, when both conditions were present, the effect was synergistic. When both factors were present in middle age, the odds ratio for developing Alzheimer's disease was 3.5.
The authors conclude that raised systolic blood pressure and hypercholesterolemia and particularly their combination during middle age significantly increase the risk of developing Alzheimer's disease. They suggest that identifying patients with these risk factors and applying interventions to reduce the long-term effect of these conditions may have a major impact on public health.