Don't ask me why or how but I must've stumbled upon a treasure trove dementia related studies recently, not unlike the blind squirrel finding the occasional nut. In any case, I want to offer you an analogy to explain my philosophy towards health care. When I was in grade school, then high school, and then college, the typical grading system went something like this: F = failure, D = low pass, C = average, B = high pass & A = honors. Or something like that. In other words, if all you wanted to do was pass, you could get by with a D grade. After all, that D grade was good enough to move you on to the next grade or even towards graduation. But for some of us, good enough just wasn't good enough. If we wanted to become a doctor, we needed to get straight A's in college which meant straight A's in high school, etc. Even a B grade wasn't good enough.
So think about Hemoglobin A1c, the running 3 month measure of sugar control. I liken it to your average trip speed on a long drive whereby you speed up & slow down & speed up again, perhaps coming to a complete stop due to traffic, stop lights or stop signs. Glucose, whether random or fasting, is represented in this scenario by your speedometer which tells you how fast you're going at that precise moment in time that you glance at it. However, that very same speedometer tells you nothing about how fast you were going a minute ago, 5 minutes ago, 30 minutes ago, an hour ago, etc.
With all this in mind, a cross-sectional study was published early online last week prior to print next month in Neurology in which the authors concluded that lower A1c within the normal reference range was associated w/better memory & larger hippocampal volume, a structure linked to Alzheimer's disease risk. Now, before you go out and ask your doctor for insulin to lower your sugars, notice that this conclusion is based upon 141 participants, half of whom were women, average age 63yo. This study says nothing about what happens if you lower your blood sugar. It's not a double-blind, placebo-controlled, randomized trial. Instead, the authors compared various domains of memory & cognition to A1c, blood glucose, insulin and magnetic resonance imaging scans. Even in those without diabetes or impaired glucose tolerance, lower A1c was linked to better delayed recall, learning ability & memory performance. Think about that before you take that next bite of food.
To arrive at their conclusion, the authors reviewed over 6 years worth of data for 1,928 adults w/normal cognitive function, who were older than 75yo at study entry. Some benefit was noted w/calcium channel blockers and even beta blockers, too, but w/o statistical significance. Ironic, isn't it then, that last week's study suggested benefit from beta blockers but not ACE inhibitors.
So what are we to make of this quandary & contradictory evidence. First, let's recall that science is never that clear cut & transparent. Second, in the big scheme of things, 5-6 year studies of 800-1900 participants is neither long nor large enough. Third, observational studies such as these are useful for developing hypotheses but not for proving cause & effect. But with all that said, I can't think of a single reason (aside from anaphylactic allergy) not to lower one's blood pressure and pray for secondary benefit, even as we wait for more definitive proof.
To arrive at their conclusion, the authors followed for close to 6 years 854 men average 77yo at study entry to the Honolulu-Asia Aging Study. All participants had hypertension but were without dementia or any cognitive impairment at baseline. Those who were taking beta blockers had a 31% lower risk of developing cognitive impairment compared to those who didn't take any blood pressure medication. So perhaps the benefit was due to lowering of hypertensive blood pressure? However, in contradiction to previous studies, use of ACE inhibitors alone was not linked to benefit, nor were diuretics, calcium channel blockers, or vasodilators.
Two steps forward, one step back, right? Was this study a fluke or a trend? You decide after reviewing the earlier studies. But more importantly, does this study apply to you? Perhaps if you're an elder male of Japanese heritage as were these participants. On the other hand, you might take a look at the bigger picture, which is that blood pressure lowering in general appears to be a good thing.