Assesing our complications risks - standard deviation, glycemic variability and other things

[LucySW]

Reposting a 2010 DiabetesMine article originally posted by @phoenix on an old thread, on how we can lower our complications risk, and what A1cs and standard deviation actually tell us about complication risk. The author cites Irl Hirsch and a colleague stating that in the DCCT trial, A1c levels only accounted for 11% of the risks for complications. I had not seen this and it is somewhat gob-smacking.

"According to an April 2008 Diabetes article, analysis of the participants in DCCT found that A1c was only responsible for 11% of the overall risk for developing microvascular complications. That means 89% of our risk for complications is coming from somewhere else. But whether that's standard deviation, environment, genetics, or something else entirely, no one knows.​

"In a recent Journal of the American Medical Association article entitled, "Beyond HbA1c: Need for Additional Markers of Risk for Diabetic Microvascular Complications," co-authored by Dr. Hirsch and Dr. Michael Brownlee of the Albert Einstein College of Medicine, the authors state that it is "crucial" to find out what causes the remaining 89% of microvascular risk. They write, "Physicians will have to realize that much remains to be done in identifying important factors contributing to microvascular complications risk, which are not captured by the HbA1c."​

(...)

"The theory went that low standard deviation, i.e. less blood sugar swings, would be a good indications that a person's risk of complications is lower than someone with a high standard deviation, even if their A1c was higher than recommended (above 7%). This is supposedly so because the wild swings in blood sugar levels supposedly take a toll on a body — possibly even more so than having slightly elevated BG levels that remain steady.

' "The fundamental question is does variability give you an independent risk for getting diabetes complications? It's the 500 pound gorilla and we just don't know," says Dr. Irl Hirsch, endocrinologist at University of Washington and a lifetime type 1 himself, who's been one of the most famous proponents of applying standard deviation to diabetes care. What's that? We don't know? Not enough evidence here?!"
​

Just throwing this back in again.

 

[SunnyExpat]

Surely it would suggest that simply keeping your BG at low as possible, for as long as possible, is the best way?
Anything below 7 on that chart, whether achieved normally, or intensively looks good though, allowing for statistical error.

 

[LucySW]

And here's another article, Gretchen Becker on the old Q of whether it's actual mean BG levels or HbA1c that better reflects complications risks. I'm interested because I'm a high glycator: my A1c is consistently higher than my mean BG (based on a Libre, ie with CGM data) ought to predict. So while my mean BG and standard deviation are good, if it was the glycation that predicted complications risk more, then I ought to work harder to get the glycation down.

There seem to be no answers on this. But it's important for some people, so posting.

 

[LucySW]

See also this, of interest to high glycators like me (albeit from another context, is HbA1c or fasting plasma blood sugar better for diagnosing diabetes).

"It’s true that glycation rates affect interpretation of HbA1c, Dr. Vigersky said. Studies have shown for a mean glucose over a three-month period, “there’s a significant splay in the data of HbA1cs. And I think you would conclude that some people are high glycators and some people are low glycators at the same blood glucose levels.” ​

"But these differences have important implications, he pointed out. “If you look at the complications of retinopathy and nephropathy, those with high glycation rates had much higher percentages, by a factor of six, compared to those with low glycation rates. So I would argue that even if we understand that there’s biologic variability and genetic variability in glycation rates, it may be beneficial to overestimate and pick up those with high glycation rates, because they in fact are at most risk of developing complications of diabetes.” "​

 

[Brunneria]

Thank you @LucySW

Lots to mull over. When I brought my BG down quite significantly (according to my meter), it affected my A1c not a jot.
So this is very useful to me.



You are a star.
But then, we knew that already.

 

[tim2000s]

That's interesting and for me, seems a good thing to here, as my Hba1C is continuously lower than the Libre prediction and average BG shows. Sadaly not such good news for you @LucySW

 

[Bluetit1802]

Thanks @LucySW very interesting, and I am also a high glycator I believe, as my A1c is always higher than my meter readings, (and I test a lot and at all times post prandial), and by quite a bit. I need to have a think about this.

 

[alaska]

Thanks for compiling these together. I've frequently seen research in recent years touching on glycaemic variability as an indicator of risk for heart disease -albeit never going into great detail why it's the case.

For type 1s/LADAs it strikes me as significant.

The DUK, NHS, DAFNE approach is based around low fat, relatively high carb and therefore leads to sharp rises followed by a more gradual dip -similar profile as a child's slide

The relatively high carb content requires relatively high insulin at each meal and increases the risk of mistakes being made.

Unless the person is a very good at judging insulin doses, this brings two common consequences:

• Higher incidence of hypos
• Or deliberately keeping sugar levels on the high side to prevent hypos

In either case, the variability of sugar levels will still be higher than someone following a lower carb diet.

On LCHF, the highs are significantly more benign and the lows are usually less severe too -as smaller mealtime insulin doses generally mean lower chance of larger errors being made.

I'm probably rambling here, but I mean to say this is very interesting.

 

[sanguine]

Thanks Lucy - another spanner in the works on interpretation and relevance of HbA1c is presumably variation in blood cell life and what influences that.

 

[tim2000s]

Thanks Lucy - another spanner in the works on interpretation and relevance of HbA1c is presumably variation in blood cell life and what influences that.

It wouldn't be a surprise to discover that a high glucose would knock the life down.

 

[Scardoc]

Imagine you live near a river and every day you wander out a few times and photograph the same part of it. Then you set up a time-lapse camera and leave it for a month. Looking at the results it's obvious that one is a snapshot and one tells a bigger picture. However, even when the river looks low and calm, can there not be life threatening currents flowing under the surface.

I'll leave you with that. Back to my peace pipe.

 

[Brunneria]

And so, my education in glycation begins... (Wiki is always a good place to springboard from)

https://en.wikipedia.org/wiki/Glycation

 

[LucySW]

Imagine you live near a river and every day you wander out a few times and photograph the same part of it. Then you set up a time-lapse camera and leave it for a month. Looking at the results it's obvious that one is a snapshot and one tells a bigger picture. However, even when the river looks low and calm, can there not be life threatening currents flowing under the surface.

I'll leave you with that. Back to my peace pipe.

Yes, but if you have a pic taken every 15 minutes, as with a CGM, you can average that to get a bigger picture too, Scardoc.

I'd like a pull on that peacepipe.

 

[LucySW]

It wouldn't be a surprise to discover that a high glucose would knock the life down.

Apparently some studies indicate this, but others indicate the opposite. Whatcha. @phoenix linked a couple of these recently.

 

[noblehead]

@LucySW,

Certainly keeping the SD as tight as possible is a must and in the book Think Like a Pancreas the author says its best to try and keep it below 2.

If you read the following it makes for interesting readings, it's about the Joslin 50 Year Medallist and a study into why many have escaped serious complications despite living with type 1 for 50-80 years, as you'll see it surprising to see that some still have functioning beta cells despite their longevity but the article also says that genes play an important part too:

http://www.joslin.org/medalist/6268.html

 

[LucySW]

Thanks Nigel. Hadn't seen that, but have seen this similar one:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4058732/pdf/WJD-5-282.pdf

Jason Fung uses this to argue that it's insulin toxicity we should work on minimising:

https://intensivedietarymanagement.com/lchf-for-type-1-diabetes/

We don't really know, do we? We just have some hypotheses. ...

 

[Scardoc]

Yes, but if you have a pic taken every 15 minutes, as with a CGM, you can average that to get a bigger picture too, Scardoc.

I'd like a pull on that peacepipe.

Puff away!

When HbA1C is involved I don't like the use of the word average, I think that muddies the waters. Sorry, I will try and keep away from the punts now.......err.....I mean puns!

 

[LucySW]

Punts downriver? That sounds nice ...