https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734630/
quote "Using a multivariable adjusted quadratic spline with HbA1c=5.2% as the cut-point, low and high HbA1c values were associated with an increased risk of all-cause mortality among individuals without diabetes."
Anything below 5.3% are as bad as numbers above 6.3%.