Alzheimer's disease (AD) is characterized by decreased neuronal activity and atrophy, while hyperactivity of neurons seems to make them resistant to aging and neurodegeneration, a phenomenon which we have paraphrased as 'use it or lose it'. Our hypothesis proposes that (1) during their functioning, neurons are damaged; (2) accumulation of damage that is not repaired is the basis of aging; (3) the vulnerability to AD is determined by the genetic background and the balance between the amount of damage and the efficiency of repair, and (4) by stimulating the brain, repair mechanisms are stimulated and cognitive reserve is increased, resulting in a decreased rate of aging and risk for AD. Environmental stimulating factors such as bilingualism/multilingualism, education, occupation, musical experience, physical exercise, and leisure activities have been reported to reduce the risk of dementia and decrease the rate of cognitive decline, although methodological problems are present.
Animals ; Brain ; pathology ; physiopathology ; Dementia ; genetics ; pathology ; physiopathology ; prevention & control ; Humans ; Models, Neurological

Periodontal disease is a predictor of stroke and cognitive impairment. The association between the number of lost teeth (an indicator of periodontal disease) and silent infarcts and cerebral white matter changes on brain CT was investigated in community-dwelling adults without dementia or stroke. Dental examination and CT were performed in 438 stroke- and dementia-free subjects older than 50 yr (mean age, 63 +/- 7.9 yr), who were recruited for an early health check-up program as part of the Prevention of Stroke and Dementia (PRESENT) project between 2009 and 2010. In unadjusted analyses, the odds ratio (OR) for silent cerebral infarcts and cerebral white matter changes for subjects with 6-10 and > 10 lost teeth was 2.3 (95% CI, 1.38-4.39; P = 0.006) and 4.2 (95% CI, 1.57-5.64; P < 0.001), respectively, as compared to subjects with 0-5 lost teeth. After adjustment for age, education, hypertension, diabetes mellitus, hyperlipidemia, and smoking, the ORs were 1.7 (95% CI, 1.08-3.69; P = 0.12) and 3.9 (95% CI, 1.27-5.02; P < 0.001), respectively. These findings suggest that severe tooth loss may be a predictor of silent cerebral infarcts and cerebral white matter changes in community-dwelling, stroke- and dementia-free adults.
Age Factors ; Aged ; Alzheimer Disease/diagnosis ; Brain/*radiography ; Cross-Sectional Studies ; Dementia/pathology/prevention & control ; Diabetes Complications/diagnosis ; Female ; Humans ; Hyperlipidemias/complications ; Hypertension/complications ; Interviews as Topic ; Male ; Middle Aged ; Odds Ratio ; Periodontal Diseases/complications/*diagnosis ; Predictive Value of Tests ; Risk Factors ; Stroke/pathology/prevention & control ; Tomography, X-Ray Computed ; Tooth Loss