Most of the studies into the protective effects of exercise against cognitive decline, dementia, and Alzheimer’s disease, followed the elderly people starting their 65s and watched the results, which were relevant to the beneficial effects in late life. However, there are some results where a large cohort of 65-79-year olds has been followed-up for around 21 years so information about physical activity during midlife was available. Those who who participated in at least “leisure-time physical activity” during midlife had significantly lower risks of dementia or Alzheimer’s disease comparing with those who did not exercise at all [1].

Another study has suggested that physical activity at even earlier ages (physical activity between ages 15 and 25 years was asked retrospectively) can improve or preserve cognitive ability in late life [2]. This cognitive decline risk reduction is at least comparable to the eisks reduction reported in studies of physical activity in older persons. Thus, midlife physical activity might be as important for preventing later cognitive decline as is physical activity at older ages.

Sources

1. Rovio S, et al. Leisure-time physical activity at midlife and the risk of dementia and Alzheimer’s disease. Lancet Neurol 2005;4:705–11
2. Dik M, Deeg DJ, Visser M, Jonker C. Early life physical activity and cognition at old age. J Clin Exp Neuropsychol 2003;25:643–53

Caffeine, the most widely consumed behaviourally active substance in the western world (Pharmacol Rev 51 1999: 83–133), has neuroprotective effects in cases of hypoxia and ischaemia (Brain Res Rev 33 2000: 258–274). Does caffeine protect against neurodegeneration in Alzheimer’s disease as it does in Parkinson’s? Researchers from Faculty of Medicine of Lisbon, Portugal, tested the hypothesis that average daily caffeine intake in the period of 20 years before the diagnosis could be lower than caffeine intake in age- and sex-matched healthy people and showed that indeed, people who was diagnosed with Alzheimer’s consumed an average 74 mg (less than one cup) while the controls had about 200 mg. ”These results, if confirmed with future prospective studies, may have a major impact on the prevention of Alzheimer’s,” concluded the researchers (Eur J Neurology, V 9, Issue 4, 2002: 377–382).

In a Canadian study, daily coffee intake decreased the risk of Alzheimer’s by 31% during a 5-year followup in
65-year old people (Am J Epidemiol 2002, 156, 445-453.). The Finland, Italy and the Netherlands Elderly (FINE) Study showed that elderly men drinking three cups of coffee daily had the least cognitive decline (Eur J Clin Nutr 2007, 61, 226-232). Tea drinking  (Am J Epidemiol, 2004, 159, 959-967.), or flavonoid intake from tea  has not been associated with a reduced risk of dementia. The low coffee consumers in mid-life had the highest occurrence of dementia and Alzheimer’s at late-life, and the highest scores on the depression scale (J Alzheimer’s Disease 16: 2009, 85–91).

One possible mechanism could involve insulin and degrading enzyme that degrades both insulin and amyloid-beta, the most suspected cause of Alzheimer’s (CNS Drugs 17, 2009, 27-45). Another mechanism is via adenosine receptors (caffein mimics effects of adenosine). It has been shown in mice that both caffeine and adenosine prevent amyloid-beta induced cognitive decline (Exp Neurol 203, 2007, 241-245).

If we could delay the onset of dementia by 2 years, we could reduce its risks by as much as 25% — all other things being equal — and one of the most effective and simple ways is physical activity (Am J Public Health 1998;88:1337– 42). Drs Rockwood and Middleton from Dalhousie University, Halifax, Canada, analyzed 7 studies of exercise effects on risks of dementia and concluded that, without exception, 65 to 93 years old men and women who exercise the most have a lower risk of dementia relative to those who exercise the least. (Alzheimer’s & Dementia 3 2007; S38–S44).

Another, large-scale study found a significant dose-response relationship between physical activity and cognitive function was conducted as part of the Nurses’ Health Study  in 18,766 women (JAMA 2004;292:1454–61). After about 10 or more years, when the women were 70 to 81 years old, those reporting the most physical activity scored higher on several baseline tests of cognitive function. During the 2 years of additional follow up, there were again significant trends for a dose-response relationship in which those reporting the most physical activity exhibited the least decline in cognitive function (JAMA 2004;292:1454–61).

Even walking was associated with a “dose-dependent” risk reduction: those walked at an easy pace for at least 1.5 hours per week had significantly higher cognitive scores than those walking less than 40 minutes per week. Higher activity levels might not be necessary for the benefit (Alzheimer Dis Assoc Disord 2004; 18:57– 64) – an increase of 30-minutes aerobic exercise frequency from 3 to 5 times per week did not result in a proportional decrease of cognitive decline in a group of 1146 women 65 years old or older.

However, for those in the higher-intensity exercise group, that worked out at least moderate intensity (more vigorously than walking), or for longer durations each day (Med Sci Sports Exerc 2001;33:772–7.) chances of cognitive impairment, Alzheimer’s, or all-cause dementia were lower (Arch Neurol 2001;58:498 –504).

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