A1C vs all cause mortality

Interesting article… maybe too much of a good thing (tight control) isn’t as great an idea as we thought


Interesting study. Good number of patients in the population. However, unless I mis-read it the findings are only applicable to non-diabetics. Complicated subject, i.e. relating a test result to causation, and the fact that they needed some complex statistics hints at the difficulties assessing the data.

1 Like

I didn’t catch that… how would it be possible for it to be applicable only to diabetics? As they’re assessing people based on elevated a1c… which means diabetes

Well I mispoke a bit, Here is what the paper says:

Excess mortality risk was observed for participants with known diabetes (hazard ratio 1.41 [95% CI 1.08–1.84]) and undiagnosed diabetes (1.63 [1.23–2.17]) but not for those with high (1.02 [0.80–1.30]) or very high diabetes risk

Ah yeah… it is kinda confusing… reading these on a little phone screen a lot gets skimmed over or lost in translation…

Here is the relevent data table. My own personal observation, is that it is slightly better to have known diabetes than undiagnosed diabetes. But even though the population was large, the number of events wasn’t huge. Clearly bad to have undiagnosed or diagnosed diabetes in this cohort compared to normal glycemic folks.


1 Like

It might have been helpful to divide the known diabetes group into 2 groups, based on A1C. Some with known diabetes but don’t manage it well, would be more like the undiagnosed group.

1 Like

Interesting. I’m not sure how relevant this is to people with diabetes, given that they state that an A1c ≤5.0 is associated with increased risk…and the number of people with diabetes who achieve that is minuscule. Those who do achieve such a low A1c are very likely putting in extraordinary efforts (such as following Dr. Bernstein) and have very strong beliefs that aren’t likely to be changed. So, not sure most people ever have to worry about the low end of that curve… It does hint that maybe aiming for an A1c <6.5% might be a good and reasonable goal.

This reminds me of another study I read about that showed a U-shaped curve for mortality risk and weight. Those who were skinny had increased risks as well as those who were obese, and those in the overweight range had the best outcomes. Maybe moderation in everything really is the key to life…


Ok, I just read through the paper twice, and the “U-shaped” association between A1C and mortality is observed only in groups of subjects who have not been diagnosed with diabetes. In the conclusion section they aren’t as careful in their wording, so you have to read the body of the paper to see that there are not any results reported in this paper about a relationship between low A1C and problems for people who are diagnosed with diabetes.

As far as the increased mortality found with low A1C in people not diagnosed with diabetes, towards the end of the paper they basically say that more research is needed to understand the connection. They did try to investigate whether they were finding worse outcomes in people with unusually low A1C simply because those people were already sick or dying which caused the low A1C. They were unable to come to a definitive conclusion on this point.

With respect to people diagnosed with diabetes, if you take all of them together as a single group, this group as a whole has worse health outcomes. We already knew this. The group of all diabetics includes people with quite high A1C, and it has been known for a long time that diabetics with high A1C have more problems.

For those of us living with diabetes, I’m not seeing any important new finding in this paper, and in particular, I’m not seeing any result suggesting too low an A1C causes harm to us.


I tend to think that in people without diagnosed diabetes, people with lower A1Cs probably have an underlying health condition. If your blood cells don’t last as long, you will have a lower A1C. And maybe they’re not lasting as long because you’re anemic or unhealthy in some other way.

That said, I suspect you’d find elevated mortality for diagnosed diabetics with a very low A1C for a different reason – hypoglycemia and higher exposure to insulin.