I would actually like to see your evidence for a normal level of 4.5%. Dr Bernstein may say it but where was he was getting it from?
Have you read this ?
http://www.mendosa.com/blog/?p=366
Moreover, two people with similar average blood glucose levels can have widely disparate HbA1cs,(as much as 3mmol/l at each end of the spectrum) and people with perfectly normal glycemia have higher HbA1cs as they age.
Have a look at this study which demonstrates the affects of ageing on HbA1c
Effect of Aging on A1C Levels in Individuals Without Diabetes
Evidence from the Framingham Offspring Study and the National Health and Nutrition Examination Survey 2001–2004
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2551641/
This was analysis of 2 large groups, in one group they all had passed OGTTs, the other all had normal fasting glucose. There were more than 5000 of them, so a big sample.
Only the youngest group had an average HbA1c in the fours and that was 4.95% and people at the outer ends of the range (97.5% percentile) were in the mid 5s.
There was a distinct trend . IN each successive age group, the average HbA1cs were higher.
(this also applied when they looked at the same groups over a number of years)
Personally my HbA1c at 5.8% is only 0,4% above the average for my age group and well below the 97.5% percentile. So I'm happy with that and would still be happy if it was over 6% . This would still be well within the normal range for my age.
I'm lucky I'm able to get to this level, I do a fair amount of exercise, I have been lower and as I said on the other thread. I was most certainly losing my hypo awareness. I'm now at a level when I have good awareness, though I realise that doctors in the UK dealing with the DVLA might not be so happy about this level.
Fortunately as Sam says the risk reduction at levels below 6.5% is negligible.