Christopher, you make a great point. In statistics the principle you’re describing (a+b=c) is the distinction made between correlation and causation. This study (and most medical research studies) are looking at correlations. Simply, “A” is associated with “B”. This does not mean A causes B.
In this study, the researchers found a strong correlation between a history of hypoglycemia requiring assistance and car accidents. Like you said, this does not NECESSARILY mean that hypoglycemia caused the accident, only that there is an association. Maybe people who have frequent hypoglycemia also happen to be people who drive poorly in general, who knows. Maybe they tend to be less responsible people and don’t pay attention when they drive.
Either way, I think it’s important to remember that the main conclusion of the authors is that it is not accurate to determine someone’s fitness to drive based on their BG control as represented by HbA1c.
The headline is misleading. Its not that they have nothing to do with each other, its the distinction between correlation and causation. Just because two things are correlated, does not mean that one causes the other. Like Christopher mentions below, ice cream sales increase in the summer, as does crime, but ice cream does not cause crime. They are only associated.
The authors note in the study that there is a statistical association between lower HbA1c and increased car accidents, but they also note that there are other factors:
“Unknown social or medical factors might explain the results. In this case, the authors point out that a major drawback of their study is that it is not randomized and drivers have free will in choosing how tightly to control their diabetes and also how carefully they drive.”
It could still be the diabetes though. History of hypoglycemia was strongly correlated with accidents. The problem is not everyone with lower HbA1c has significant hypoglycemia, but certainly some of them do, and this would lead to the appearance of an association between A1c and accidents.
Christopher, I too enjoy the back and forth and the exchange of perspective, but again I think I may not have made myself as clear as I should. I apologize in advance for the following argument – it’s a bit academic but I think it’s important to be clear on this idea of correlation and causation.
In fact, I do agree with the findings of this study, but I strongly disagree with the interpretation that there is any finding of causation. The study found that risk of crash increased as HbA1c levels decreased and that there is a 4-fold increase in risk of crash in those with a history of hypoglycemia needing assistance. The key here is to understand how the statistical analysis works. This type of study does NOT establish causation. To establish cause, they would need to know the BG values taken at the time of the crash. This is not the data that they present.
Risk is not the same thing as causation. The authors, in the discussion section of the actual study state the following: “A major limitation of our research relates to the nonrandomized design and sample selection. That is, adults with diabetes self-select how to control their glucose as well as how to drive a vehicle. One explanation for the association, therefore, could be that those who are stringent about controlling their blood glucose are paradoxically more careless about driving a vehicle. Another explanation could be that tightly controlled patients drive in more dangerous settings. A third explanation could be that unreported alcohol consumption influences both driving risk and glucose control (e.g., impaired liver glucogenesis). Many other biases are possible…” ( Reference: http://bit.ly/8nvYwL )
Basically, what the authors are saying is that yes, there is increased risk of crashes with these diabetics, but that there are many other possible explanations. Of course, the most likely is that hypoglycemia contributed, but there is no way that this could be known, not by the authors of the study, and not by you or I.
As far as the headline is concerned, I agree that I personally do not find the headline misleading, but the fact that so many people here (and I’m sure elsewhere) were able to misinterpret the findings based on the headline alone suggests to me that there may have been a better title. Perhaps something along the lines of, “Car Crash Risk Maybe Associated with Tight Glucose Control and Low Blood Sugar.” However, I’m not a journalist, I’m a scientist and all I can speak on is the research.
It pays greatly to test before every drive. I wear a CGM but had a sensor fail today at 11:00 AM. I tested before commuting home and was at 46. Scary thing is, I felt fine. Dammit!
I disagree because I have tighter control then I did many years ago. My tighter control consists of constant monitoring. When I am ready to leave home I test. When I arrive at my destination and know I will be walking I test. When I am leaving and before starting my car I test…in other words I’m constantly testing.
I consider 7.4 and 7.8 to be out of control. The study, in my opinion, was measuring people who were bouncing up and down, highs and lows. Neither of the two groups, non-random as they were, represent tight control. Significance in this kind of a study is meaningless. Those were not “Diabetics with Tight Blood Sugar Control”.
OK, I’m sorry if my persistence is annoying anyone, but again the results are being misinterpreted. First, the numbers you’re quoting are mean (average) A1c values in a range of analyzed A1c. The authors never define this as tight control, so I’m a bit confused as to why you cite those numbers. Second, all they are saying in that section of the paper is that risk goes up as HbA1c goes down. From the study: “This association was equivalent to a 26% increase in the risk of a crash for each 1% reduction in HbA1c (odds ratio = 1.26, 95% confidence interval 1.03–1.54). The finding was evident across the range of HbA1c values and suggested that the risk of a crash in the bottom quartile was more than twice the risk in the top quartile.”
So the 25% with the lowest A1cs had two-times the risk as the 25% with the highest. That is all.
Again, the significance of this type of study is not “meaningless”. And again, the title of the journal article is what is confusing the issue. Forget for one moment that they used the phrase “tight control.” If you ignore the title (which is meaningless with regard to the results of the study), the fact still remains that the results determined that risk of crash increased as HbA1c decreased and that people with a history of significant hypoglycemia were 4 times as likely to crash.
Of course, there are limitations to the study, but the significance is not meaningless! In fact, results like this HELP change laws that affect diabetics! From the authors: “At a minimum, the data suggest that a patient’s HbA1c level is neither necessary nor sufficient for determining fitness-to-drive. Whether a comprehensive medical review, functional performance assessment, formal driving test, detailed record of hypoglycemia episodes, or other measure could be more accurate and cost-effective remains a topic for future research.”
I feel like I’m repeating myself, but I really want this to be understood. These researchers are saying that OTHER FACTORS could be contributing to these crashes and that the current laws that RESTRICT diabetics based on HbA1c alone are too simplistic. This type of research helps diabetics. It demonstrates that we are more than just walking A1c scores. Please, everyone, forget the “tight control” title, it really seems to be throwing things off…
Given that the study compared 7.5 with 7.9 A1c diabetics, it seems to have left out the “tight control” diabetics. Also, it is a U or Toronto study that tracked diabetic from Jan 2005 through Jan 2007. That is a long time ago in diabetic years.
The glycemic averages for 7.5 is 186 and 7.9 is 204 hardly a stat for “tight control” of BGs. Good control. but not what is not defined as tight.
What the study is assuming is that if you are averaging a BG of > than 200, which is now recognized as an A1c that may increase a variety if complication as noted in the most recent ADA medical recommendations.
Wel to this assumption I have to say “bi… me” and take the study and put it back in the old file cabinet and don’t take any pride in the assumptions made. Particularly since the study used old data, no “tightly controlled” D’s and did not evaluation the general health and management practices of the D’s in the study.
I was quite upset with what I thought the general public would read and understand from this study…simply generating fear rather than understanding the difficulty in determing which drivers are “safe”. BUT i did think that this study might help me lobby my Canadian government in providing pumps and CGMs for people with diabetes. Would that not really improve this driving situation if one could have access to this technology? Yes I know that one would still need some finger testing and being careful…but in my eyes the technology would be a tremendous help!!
All the money and time spent on a worthless topic. I have a monkey
who could answer this without another worthless study.
I feel those who try for too tight of control are doing themselves a
great injustice, regarding their quality of life. I feel those who are always in a tight
control mode are letting this disease dictate too much on how to live one’s
life. I believe you can’t expect to have perfect blood sugars most of the time
when you are a Diabetic. I can only imagine how much stress it takes to
achieve what is essentially unachievable, to be perfect with a disfunctional
Pancreas.
That may be a perspective from your own experience. There is a lot more to controlling BG that keeping the BG low, that is not a definition of tight control, only a label by other to, again, lump together a bunch or T1D.
The danger of low BGs, or hypo unawareness, does not come from trying to achieve low BG or as you stated, “tight control,” it comes from not planing and taking care to not end up low and/or out of control while driving a vehicle.
I think it would be great if this site becomes a “no label” site and embraces the unique individuality of being a T1D.
Sorry to pop in on this Dave, but the page you linked to states clearly what Scott said. tight control is keeping BGs in normal range, not keeping BGs low.
I find this rather ironic. Before I went on the pump, back when I was using NPH and Regular, I had rather poor control, with A1c’s routinely well over 9%. I had also totally lost my hypo awareness (thank you NPH), and I ended up nearly passing out while driving from a sudden low. I had tested before I got into the car and tested out at 95; within 10 minutes my bg had dropped to the point where I was getting confused, within another 10 minutes I was down to the low 20’s. Luckily no one got hurt and a cop found me pulled off the road and trying to get the gear into park, recognized the low blood sugar, and called the paramedics.
Fast forward…my doc put me on humalog via pump. I now have excellent control. My A1c’s are routinely between 6.5 to 6.7%, and I have hypo awareness back. I haven’t had a serious low (below 50) in over 7 years.
So I guess the question is…what exactly do they mean when they say “tight control.”
I also kind of agree with Stephen who said “The danger of low BGs, or hypo unawareness, does not come from trying to achieve low BG or as you stated, “tight control,” it comes from not planing and taking care to not end up low and/or out of control while driving a vehicle.” With the exception that for those with hypo unawareness and real sudden drops, it’s very difficult. For myself, to this day, despite having great hypo awareness and hardly ever having a bg lower than the 60’s, with those occasional ones in the 50’s, I still test every single time before getting into the car to drive.
I disagree with the study. I am a retired cop, 32 years, and in 24 of those years I only handled a couple of accidents involving diabetics with lows . The rest of the time it was Hypo events outside of a motor vehicle. In auto accidents there is host of variables that can contribute to an accident, poor road design, vehicle problems, weather factors and so on. Just focusing on A1C’s is a little too narrow for me.
I would be curious if all of Dr Bernsteins patients with low A1C’s, that are very well controlled, and in accidents would have a higher or lower accident percentage vs the general population? That might give better insight into this question.
I do agree that testing before one drives is a good idea, knowing what your BG numbers on average are, and carrying something to avoid a Hypo event is a must. Shannon your right, insurance is a game of statistics, groups, and outcomes and a few can make life miserable for all.
Well let me clarify more. The accidents I had in mind are the ones where the person was passed out, caused a major crash, and had medical ID, or paramedics, Emergency Room staff, or the Medical Examiner told me the person was diabetic. For every 500 drivers I stopped and arrested for DWI there where only a couple having a Hypo event. My point in all this is that people driving under the influence, using cell phones and yes TEXTING are a greater threat to the public at large than diabetics.
Diabetics do cause accidents and sometimes serious ones. I agree with you all it takes a moment of distraction and it can be disaster. The question still remains, do tightly controlled A1C diabetics have a higher accident rate? Perhaps…Then it comes down to how the study was conducted and what factors did they consider in the study? ummmm Then carrying it a step further do people with heart conditions, suffer seizures, and other medical conditions have a higher accident rate than tightly controlled A1C’ diaetics?
I was looking at the whole of my years pounding the pavement. So in the scope of things I am more likely to have an accident with a driver TEXTING on the road than I am with another diabetic with a tightly controlled A1C.
In my opinion, a more appropriate question would be;
Are diabetics today (2009) at a higher risk for becoming impaired? YES
why? Bringing fast acting insulins to the masses.
Factors to consider LACK OF PREEMPTING warning labels on insulin vials,
lack of education… lack of teachable moments… lack of personal responsibility…
incorporating factors as simple as labeling drivers licenses, that can depict diabetes
and therefore set standards of practice for the individuals ie, having equipment meters, glucose,
etc. and proof of use, frequent testing when driving. Same as people that I wear glasses and its
on my license as it should be… you see where I’m going here
I am from the standpoint that diabetics do NOT in the majority of cases have “episodes” or
“attacks” the only way to preempt driving impaired is to have the information to make responsible
decisions…
Testing before you turn the key
Is simply a diabetic’s responsibility!
is the start and than for each known incident investigation of circumstances and public sharing of
that to enhance the personal experience of all diabetics and those that know, love or deal with the treatment and or back lash of even acutely mismanaged diabetes. The impaired diabetic driver is
like no other impairment… its a human being in a fight or flight response to impaired cognitive function on the way to being totally incoherent out of control yet not unconscious (very dangerous)… and eventually
losing consciousness… all in a time line that has numerous variables (like how the body can respond, insulin on board, etc. Anyone taking insulin no matter what their previous history of care is at risk, and anyone regardless of their previous A1c could act or not act in a way that acutely puts them in this situation… NO Doctor can certify what another human being can or willl do on any given day.
Just as CGM shows us an enormous amount of information and is testimony to the complexity of diabetes management… Its the individual that should have the responsibility to prevent lows… whether they have a positive healthy diabetes plan on going is irrelative, its the moments behind the wheel that need to be proactive to imminient acute hypoglycemia prevention.
When a diabetic takes their condition to the road it should be open to complete public scrutiny… now that said the primary focus is to educate the public, not crusify any/ all diabetics or place undue hardships on the diabetic population. Family, friends, law enforcement, employers etc. all need an improved education and awareness of the diabetes condition…
If unaddressed as it has been for over the last decade since Humalog. We will see more accidents that happen when the greatest number of the population is at risk … think about it… meal times , before and afterwork… when there are a greater number of people on the roads…
Diabetes advocate, trying to make the world a more diabetic user friendly place, dedicating every waking moment to diabetes awareness and we have miles to go before we sleep
Sandra gotinsulin45@msn.com
People who keep their BG’s tightly controlled are at more of a risk for hypoglycemia than are those who do not. However, I personally think anyone who is working towards tight control needs to realize the risk of experiencing a hypoglycemic episode while behind the wheel of a car. I have kept my A1C in the low to mid 6’s for many years. I personally have always tested my BG before getting behind the wheel of a car, and I continue to do so. I think that is what all responsible insulin-dependent diabetics should do!
Hi Dave,
My experience differs in that my daughter was diagnosed in 99 as a toddler… Having been in the medical field for 20 yrs prior I found that diabetes was such a shrouded condition… Not in the mainstream of media in 99 even though it was evolving rapidly both technologically and pharmaceutically, there was no limelight and recognition and therefore no changes for what general knowledge is out there about diabetes… and diabetes is not your grandmas diabetes today! Surprisingly let me just say NPH used creatively can be a very productive basal even today… Given in smaller multidoses you can titer basal closer to pumping than … the MDI of Lantus and a faster insulin for bolusing…
Lantus holds questions for me. Let’s say I have no regrets not using Lantus without the long term effects it may or may not have…
I believe that the control that is possible today lends it self to people living closer to the edge, and that fall from one fall from grace is a lesson that’s cost could utlimately take lives when it occurs while operating a motor vechicle… That said I also believe the key is not the insulins but the knowledge to analyse blood sugar and institute management safeguards not for ultimate long term health goals primarily but for the impairment brought on by acute mismanagement… which could be as simply as skipping a meal or over treating on a given day. Limits on supplies that don’t allow for frequent testing is a huge deteriment… I don’t want regulations on anyone’s personal diabetes management goals like A1c s … I do want people to be responsible and equipped both literalily and with knowledge to know how not to endanger themselves and us while behind the wheel. Granted people don’t leave their homes thinking I am going to go out and drive at 100miles an hour going the wrong way on a US Highway with there own child in the car ending in a crash that takes that child’s life…
it happens, and than there are crashes at rush hour when several cars pile up with fatalies and I have to ask why isn’t the story told as to what lead up to the crash… we are a proactive society, yet with driving while diabetic doesn’t seem to register that the ONLY legitament action is to test and act appropriately BEFORE tradgities happen.
I have hypoglycemia and knowI the feeling but I carry a meter and tabs etc. The thought that someone is really on anything less than testing is down right scary to me.
That is one bullet in the statement. It is NOT a summary of the context of the information.
I beg to differ with your stating that I was incorrect because there was a lot more content in the page about advantages of tighter control of bg.
My point is that statements about T1Ds that are narrow or infer that “all” or “they” or “diabetics”, followed by a specific result or characteristic is usually not credible.
There are to many factor that play a role in the management of diabetes and living with it 24/7/365…successfully or unsuccessfully.
Please lighten up on those that may see things differently than you Dave.
Just kidding