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<blockquote data-quote="LittleGreyCat" data-source="post: 1612565" data-attributes="member: 6467"><p>Haven't read the references, but isn't one of the issues that the calculation is based on the average life span of the red blood cells?</p><p>Ignoring for the moment another point raised, that the glycation of red blood cells changes up and down (I would assume slowly) as BG levels go up and down (which makes it even more complicated) let us assume that new red blood cells record the BG level at the moment that they are created, then preserve this value (effectively a meter reading) until they are destroyed.</p><p>Let us further assume that red blood cells have an average life of 100 to 120 days (giving a mean age of 50 to 60 days). This suggests that after 100 days (just over 3 month usually) there could be a significant die off and by 4 months nearly all the red blood cells are gone. However we are talking averages and some red blood cells could well have died off before the 3 month mark.</p><p>So HbA1c is likely to most accurately reflect the period where you have 100% of the blood cells surviving which presumably is at least 4-6 weeks, probably 8.</p><p>After that, assuming a 10 week/70 day range before the old red cells really start to decline I assume you would mathematically deprecate the portion of the red blood cells consisting of old red cells. That is, after 10 weeks you can no longer assume that the red blood cells are as accurate as the newly minted.</p><p></p><p>O.K. now I have argued myself into a pit of confusion.</p><p></p><p>Too many unknowns.</p><p></p><p>Thrashing about did raise one question. I assume that women with functioning ovaries have a higher turnover in red blood cells than men due to monthly periods, but that just reduces the total red cell count not the balance? Or do two monthly cycles reduce the percentage of old red cells and increase the percentage of brand new?</p><p></p><p>I think I will go somewhere quiet and stop thinking for a bit.</p></blockquote><p></p>
[QUOTE="LittleGreyCat, post: 1612565, member: 6467"] Haven't read the references, but isn't one of the issues that the calculation is based on the average life span of the red blood cells? Ignoring for the moment another point raised, that the glycation of red blood cells changes up and down (I would assume slowly) as BG levels go up and down (which makes it even more complicated) let us assume that new red blood cells record the BG level at the moment that they are created, then preserve this value (effectively a meter reading) until they are destroyed. Let us further assume that red blood cells have an average life of 100 to 120 days (giving a mean age of 50 to 60 days). This suggests that after 100 days (just over 3 month usually) there could be a significant die off and by 4 months nearly all the red blood cells are gone. However we are talking averages and some red blood cells could well have died off before the 3 month mark. So HbA1c is likely to most accurately reflect the period where you have 100% of the blood cells surviving which presumably is at least 4-6 weeks, probably 8. After that, assuming a 10 week/70 day range before the old red cells really start to decline I assume you would mathematically deprecate the portion of the red blood cells consisting of old red cells. That is, after 10 weeks you can no longer assume that the red blood cells are as accurate as the newly minted. O.K. now I have argued myself into a pit of confusion. Too many unknowns. Thrashing about did raise one question. I assume that women with functioning ovaries have a higher turnover in red blood cells than men due to monthly periods, but that just reduces the total red cell count not the balance? Or do two monthly cycles reduce the percentage of old red cells and increase the percentage of brand new? I think I will go somewhere quiet and stop thinking for a bit. [/QUOTE]
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