Design of the trial The data reported in this study are derived from the cognitive testing and determination of humoral growth factors at the time of the survey 1 (recruitment phase). To determine whether extensive endurance training enhances cognitive abilities in the elderly, we plan to compare longitudinally the outcomes of various neuropsychological tests and humoral markers in elderly marathon runners or bicyclists with controls matched for age, sex, and years of education at the time of the survey 2 (5-year follow-up) and at the time of the survey 3 (10-year follow-up). Runners participating in the 2008 Wachau half marathon (21,2 km) and the Vienna City marathon (42,5 km) as well as bicyclists participating at the Corinthian marathon (180km) were recruited with the assistance of the organizers and via personal contacts. Runners or bicyclists were eligible for inclusion in the study if (a) they had participated in at least one of these 3 marathons in the preceding two years, (b) were still in continuous training during the recruitment phase (at least 2 hours/week) and (c) were over the age of 60. Exclusion criteria were (a) present or past exposure to neurotoxic substances (b) if they did not speak German as their native language (verbal intelligence) (c) diseases that markedly affect CNS functions: for example, cerebrovascular stroke, brain tumor, depression, Alzheimer's disease, epilepsy, multiple sclerosis, Parkinson's disease, etc. (d) manifest cardiovascular disease, (e) chronic alcoholism (daily alcohol intake > 60 g or diagnosed history of alcoholism) and (f) unwillingness to give informed consent. Controls were subsequently contacted via personal contact and three additional advertisements (two in an Austrian newspaper ("Krone") and one in an Austrian bicyclist journal ("Bicyclist Sports"). The controls were matched according to age, sex and years of education. Detailed information about education, smoking habits, family history, exercise training and medication was obtained. All participants had an extensive medical evaluation carried out by an experienced internal specialist including blood withdrawal when entering the study. Since it has been shown that humoral growth factor levels can vary with the circadian rhythm , all examinations were started between 10 am and 10.30 am. In cases where the examination revealed neurological abnormalities, participants were additionally examined by a neurologist. Besides the physical examination with blood withdrawal described above, the study protocol included an ergometry, neuropsychological testing, the use of a set of questionnaires and magnetic resonance imaging. All participants underwent the study protocol tests in the above-mentioned same chronological order.