(1) Can someone link me to the study/article that indicates that 140 is the threshold for microvascular damage from high BG? I see this number thrown around a lot so I’d like to see where it comes from.
(2) Is there a threshold below 140 where microvascular damage still has a propensity to occur? I’ve seen some posts indicating that some people start to correct at 110, which I couldn’t imagine doing, but is there anything to indicate that it might be smart to start correcting at a number lower than 140 assuming that number was completely stable (i.e. no food or bolus on board and perfectly stable basal)?
re question #2, it’s always very situational. If a number is “completely stable” and is high (> 100), I will hit it with a little bit of insulin to get it where it’s supposed to be. Or maybe walk the dog. Really, what I’ll do a lot of the time is have the insulin, walk the dog and then see that the “tail” of the prior insulin, that didn’t show up on my pump as IOB, pushed it down and now it’s 87 so I’ll have a light beer to correct it. I’m happy, the dog is happy, we are all happy. I have my CGM set to “alert” me when it hits 130. Sometimes that’s about where it peaks postparandially but I’d rather start investigating it when it’s there than when it’s 140+ given, of course, that 130 on the CGM might mean that it’s 145-160 on the meter, depending on the other variables. I still partake of the frequent snacks so I don’t have a lot of time windows during the day when the number is “completely stable” as you defined it. There’s alway something “on board”.
http://www.phlaunt.com/diabetes/14045678.php has some info on studies, i’m still reading them so not sure if they are super relevant…
Well, Jenny Ruhl has a bunch of pointers to studies supporting the idea that bad stuff happens over 140 mg/dl. She also points to the AACE statement on glycemic control, but that is dated to 2001 (although it is still “current”). The AACE statement also supports the 140 mg/dl threshold.
Personally, I set very aggressive “targets.” I want to be > 140 mg/dl 2 hrs after a meal less than 5% of the time. Generally, I don’t worry about how high I peak between bolus/eating and two hours. But, I want to see a number > 140 mg/dl at 2hrs ess than once or twice a week. And usually, I am pretty good, but I will eat out or make a mistake once or twice a week. But that is my goal, not my correction strategy.
I found that I was having problems correcting after meals, I concluded that I probably had an ISF of something like 50. Given that I am on an MDI, my chances of properly correcting a 140 mg/dl at 2hrs with a single unit was about Zero. So I moved my correction threshold at 2hrs to 180 mg/dl. I haven’t corrected in weeks. If I am 140 mg/dl at 2hrs, since I still produce some insulin, I will tend to slowly drift downwards and after an hour or two will usually be normalized (unless I had a 2lb steak). If I am still high at my next meal, I will factor the correction into my meal bolus.
DCCT information shows there is no threshold below which damage does not occur in a T1.
The DCCT does a very good job of convincing that the lower the average bg, the less the damage or the slower it occurs. But they didn’t find any magic number below which the risk/damage goes to zero.
I think too that doctors are averse to doing studies of dangerous lunatics (cough cough) who aim for post-parandials of 110 or whatever becaue this, in turn, leads to A1C of > 6.0 which is viewed as ‘hazardous’.
Just FYI, an average bg of 140 corresponds to an A1C of 6.5.
If you look at the detailed charts, the risk is not gone at an A1C of 6.5, in fact all the studies I’ve seen that the risk at an A1C of 6.5 is way higher than at 6.0 or 5.5. Many of the studies find the risk for damage to be best correlated with A1C, and not fasting glucose and not random glucose.
oops, I mean < 6.0!
This must all be balanced against the risks of damage due to hypoglycemia…and where you prefer to sit on the risk/reward curve. While it is true that the data show lower the better as far as microvascular complications, etc. you can clearly see the curves are leveling out and the incremental improvement from 6.5, say to 6 is less than 7.5 to 7, etc.
What isn’t shown on these curves is incidence of severe hypoglycemia. The key to pushing down further on A1C while
minimizing hypoglycemic incidences is getting the variability down - smaller standard deviation. Technolog like pumps
and CGMs help with this by allowing smaller doses, more frequent monitoring, etc. Faster insulins or better delivery methods
will also help.
Thanks for raising this great topic. Several others have noted the increased risk of severe hypos with lower A1c levels (<6.0%). While this may be statistically generally true for a large group, I believe that exceptions do exist.
At my last endo appointment I solicited my doctor’s support to shoot for a sub 6.0% A1c. Even though my doctor knows that I am very vigilant about hypos (I fingerstick about 15 times per day, use a CGM, and live with a hypo-alert dog), my doctor would not support that goal for me. What a turn-off!
I haven’t been back to him for six months and at this point I see the requisite 15 minute endo interview four times a year as a somewhat dubious exercise. Up until this year I’ve religiously visited an endo 4x/year for the last 27 years. All I really want from my doctor at this time is Rx’s and lab orders. Sorry for the digression.
I think it’s a worthy exercise to keep your BG’s as close to normal as possible while keeping severe hypos to a minimum.
Great thread!
Well said Sally, I totally agree.
What’s interesting to me is the sudden sharp rise at A1c’s above 5.5. Of course, diabetes is like walking a tightrope, and the issue of safety is paramount, so it’s a pretty individual decision as to what fasting, PP, and sleeptime BGs a person should aim for. I just don’t think there is any clearcut answer.
Low carb isn’t the only management approach that makes it possible to safely aim for a sub 6% A1c. I don’t low carb and I can safely keep an A1c in the 5s. I do count my carbs very carefully and I keep my diet simple.
Dr. Bernstein’s normal - an average of 83 with a standard deviation of 5 - might be a wonderful ideal but I don’t see it as more than that. We suffer from a disease and no matter how well we manage it, that has consequences.
Maurie
I would agree, there is a great variation in how well different people are able to control their blood sugar in the face of different levels of carbs in their diet. However, many, if not most will find blood sugar control easier with lower dietary carbs. And remember, by the ADA definition, anything below 45% of calories from carbs is “low carb.” For a normal size man with a diet of 2000 calories/day, that is 225 g of carbs. Even with my luck of having remaining insulin production, I could not eat a diet with > 225 g carbs and still maintain an A1c < 6%. You are fortunate.
If that were the case I’d be long gone by now. Though a high A1C for me would be in the 8’s I’ve probably had hundreds of thousands of readings well over 250 for 36 years. In fact 90% of my morning sugars in the last 2 months have been between 250 and 300. In less then a decade I will be in prime heart attack years but don’t have much confidence I will sail through it.
I think you have a point, that there is often a kink in the graph right around 5.5 or so. But still, the graph isn’t indicating zero risk below an A1C of 5.5 (or equivalent average bg).
Yet the “magic 140 number” crowd claims that it’s like an “on/off” switch, and as long as you’re below 140 the damage switch of off.
Some folks look at the “magic 140 number” that they read somewhere on the internet, which implied that having a single number above 140 means instant blindness, kidney failure, and gangrenous limbs. Maybe they just give up at that point.
But I look at the DCCT and other truly detailed studies, and see that any improvement in bg control (no matter how incremental, no matter whether it’s average bg or peak bg) will have benefits. And that there is no magic number below which the risks of complications simply disappears.
I think my viewpoint is superior and actually supported by the detailed data from many long term studies (I like the DCCT best because they have perhaps the longest baseline, and it’s one that my docs as a kid were involved in, but UKPDS has very similar charts). Yet there’s lots of folks on the internet who have chosen 140 as a magic cutoff point, and that’s quoted way more often in the discussion boards than any detailed DCCT study.
I always consider myself fortunate :-). But I’m not the only medium carber here who works hard with reasonable results - AcidRock, Jags, Julie - who hasn’t been around much since here new baby was born - all eat above the 120 carbs per day which is what I use as a low carb cut-off.
Maurie
- I think 140 mg/dl seems like a reasonable number to infer that there is minor damage happening in your body. I believe that research or tests of this would be difficult to show the risk/damage. But of course more damage occurs and occurs faster at higer BGs. The best data we have (IMO) is the DCCT data that Tim has cited. A 140 mg/dl average equates to an A1c of 6.5% and as the DCCT graphs show, there is an increased risk of complications, albeit lower.
I also am starting to vastly believe that hypos under the 60-65 mg/dl threshold cause cognative damage as well. The threshold for hypo damage would be the lowest BG that a normal fasting person can achieve. Damage/risk from hypos would be to the neurlogical system and most likely cognitive as the brain’s main source of food is glucose. Damage/risk from hypos is likely similar to that of hypers in that the more out of range you are and the longer you are there, the worse it is.
This of course leads full circle to the often discussed topic of achieving the lowest possible Standard Deviation. It is very easy for diabetics to feel the need to walk a smal tight rope of an “acceptable” range with very real risks at either end of the BG spectrum.
- I think non-pumpers think correcting a 110 is going overboard and they might be right. When pumping if I have a 110 reading (target 100) and no insulin on board, then the pump will recomend a minisule correction, like 0.10 Units. Almost nothing and barely a nudge in the right direction.
I haven’t read Bernstein’s book yet, and perhaps he has data to show that 83 with SD of 5 is what non-diabetics acheive…but my guess is if all of us use our meters on our non-diabetic friends and family 2 hours post-prandial, we will see quite a few outside this range.
A healthy body has very tight glycemic control. We can try to mimic this control but we have to accept that we will make mistakes and our tools are less sophisticated than Beta cells and Liver. Complications are the summary of the big and small deviations we have experienced over time. Thus I think it is always worth to strive for better glucose control. Like Tim I think any improvement in bg control will have benefits and the statistics strongly support this.