A study involving 125 younger (average age 19) and older (average age 69) adults has revealed that while younger adults showed better explicit learning, older adults were better at implicit learning. Implicit memory is our unconscious memory, which influences behavior without our awareness.

In the study, participants pressed buttons in response to the colors of words and random letter strings — only the colors were relevant, not the words themselves. They then completed word fragments. In one condition, they were told to use words from the earlier color task to complete the fragments (a test of explicit memory); in the other, this task wasn’t mentioned (a test of implicit memory).

Older adults showed better implicit than explicit memory and better implicit memory than the younger, while the reverse was true for the younger adults. However, on a further test which required younger participants to engage in a number task simultaneously with the color task, younger adults behaved like older ones.

The findings indicate that shallower and less focused processing goes on during multitasking, and (but not inevitably!) with age. The fact that younger adults behaved like older ones when distracted points to the problem, for which we now have quite a body of evidence: with age, we tend to become more easily distracted.

The new label of ‘metabolic syndrome’ applies to those having three or more of the following risk factors: high blood pressure, excess belly fat, higher than normal triglycerides, high blood sugar and low high-density lipoprotein (HDL) cholesterol (the "good" cholesterol). Metabolic syndrome has been linked to increased risk of heart attack.

A new French study, involving over 7,000 older adults (65+) has found that those with metabolic syndrome were 20% more likely to show cognitive decline on a memory test (MMSE) over a two or four year interval. They were also 13% more likely to show cognitive decline on a visual working memory test. Specifically, higher triglycerides and low HDL cholesterol were linked to poorer memory scores; diabetes (but not higher fasting blood sugar) was linked to poorer visual working memory and word fluency scores.

The findings point to the importance of managing the symptoms of metabolic syndrome.

High cholesterol and blood pressure in middle age tied to early memory problems

Another study, involving some 4800 middle-aged adults (average age 55), has found that those with higher cardiovascular risk were more likely to have lower cognitive function and a faster rate of cognitive decline over a 10-year period. A 10% higher cardiovascular risk was associated not only with increased rate of overall mental decline, but also poorer cognitive test scores in all areas except reasoning for men and fluency for women.

The cardiovascular risk score is based on age, sex, HDL cholesterol, total cholesterol, systolic blood pressure and whether participants smoked or had diabetes.

Memory problems may be sign of stroke risk

A very large study (part of the REGARDS study) tested people age 45 and older (average age 67) who had never had a stroke. Some 14,842 people took a verbal fluency test, and 17,851 people took a word recall memory test. In the next 4.5 years, 123 participants who had taken the verbal fluency test and 129 participants who had taken the memory test experienced a stroke.

Those who had scored in the bottom 20% for verbal fluency were 3.6 times more likely to develop a stroke than those who scored in the top 20%. For the memory test, those who scored in the bottom 20% were 3.5 times more likely to have a stroke than those in the top quintile.

The effect was greatest at the younger ages. At age 50, those who scored in the bottom quintile of the memory test were 9.4 times more likely to later have a stroke than those in the top quintile.

Together, these studies, which are consistent with many previous studies, confirm that cardiovascular problems and diabetes add to the risk of greater cognitive decline (and possible dementia) in old age. And point to the importance of treating these problems as soon as they appear.

Another study has come out proclaiming the cognitive benefits of walking for older adults. Previously sedentary adults aged 55-80 who walked around a track for 40 minutes on three days a week for a year increased the size of their hippocampus, as well as their level of BDNF. Those assigned to a stretching routine showed no such growth. There were 120 participants in the study.

The growth of around 2% contrasts with the average loss of 1.4% hippocampal tissue in the stretching group — an amount of atrophy considered “normal” with age. Although both groups improved their performance on a computerized spatial memory test, the walkers improved more.

The findings are consistent with a number of animal studies showing aerobic exercise increases neurogenesis and BDNF in the hippocampus, and human studies pointing to a lower risk of cognitive decline and dementia in those who walk regularly.

In a study in which 78 healthy elders were given 5 different tests and then tested for cognitive performance 18 months later, two tests combined to correctly predict nearly 80% of those who developed significant cognitive decline. These tests were a blood test to identify presence of the ‘Alzheimer’s gene’ (APOE4), and a 5-minute fMRI imaging scan showing brain activity during mental tasks.

The gene test in itself correctly classified 61.5% of participants (aged 65-88; mean age 73), showing what a strong risk factor this is, but when taken with activity on the fMRI test, the two together correctly classified 78.9% of participants. Age, years of education, gender and family history of dementia were not accurate predictors of future cognitive decline. A smaller hippocampus was also associated with a greater risk of cognitive decline.

These two tests are readily available and not time-consuming, and may be useful in identifying those at risk of MCI and dementia.

A six-year study involving over 1200 older women (70+) has found that low amounts of albumin in the urine, at levels not traditionally considered clinically significant, strongly predict faster cognitive decline in older women. Participants with a urinary albumin-to-creatinine ratio of >5 mcg/mg at the start of the study experienced cognitive decline at a rate 2 to 7 times faster in all cognitive measures than that attributed to aging alone over an average 6 years of follow-up. The ability most affected was verbal fluency. Albuminuria may be an early marker of diffuse vascular disease.

Data from 19,399 individuals participating in the Renal Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, of whom 1,184 (6.1%) developed cognitive impairment over an average follow-up of 3.8 years, has found that those with albuminuria were 1.31-1.57 times more likely to develop cognitive impairment compared to individuals without albuminuria. This association was strongest for individuals with normal kidney function. Conversely, low kidney function was associated with a higher risk for developing cognitive impairment only among individuals without albuminuria. Surprisingly, individuals with albuminuria and normal kidney function had a higher probability for developing cognitive impairment as compared to individuals with moderate reductions in kidney function in the absence of albuminuria.

Both albuminuria and low kidney function are characteristics of kidney disease.