September 27, 2009

Great News: Life Expenctancy of People with Type 2 Diabetes Same as General Population

A brand new Dutch study published in PLos ONE came up with a dramatic finding that should reassure everyone diagnosed with Type 2 diabetes that their condition is not, necessarily, a death sentence.

Since this study did not tout the usefulness any particular drug it got no play in the health media. But it may be the most important study published in the past couple months.

Here's the full text of the study:

Life Expectancy in a Large Cohort of Type 2 Diabetes Patients Treated in Primary Care (ZODIAC-10) Helen L. Lutgers et al. PLoS ONE 4(8): e6817. doi:10.1371/journal.pone.0006817

The authors' idea was to test the idea that the development of effective drug treatments for cardiovascular disease (i.e. ACE inhibitors, Statins, etc.) which have greatly improved survival for the non-diabetic population over the past decade might have also improved the survival of people with Type 2 Diabetes.

What they concluded is that "This study shows a normal life expectancy in a cohort of subjects with type 2 diabetes patients in primary care when compared to the general population."

Analyzing factors that predicted the likelihood of death, the study isolated only two: "a history of cardiovascular disease: hazard ratio (HR) 1.71 (95% confidence interval (CI) 1.23–2.37), and HR 2.59 (95% CI 1.56–4.28); and albuminuria: HR 1.72 (95% CI 1.26–2.35), and HR 1.83 (95% CI 1.17–2.89)." Albuminuria means "protein in the urine" and is a marker damage to the kidney's filtration units.

Interestingly, smoking, HbA1c, systolic blood pressure and diabetes duration did not predict the likelihood of death within the group of people with Type 2 Diabetes.

Here is the most salient data from the study. I urge you to click on the link and read it in full:

Table 1

The participants in this study mostly had A1cs around 7%. The researchers note that only 7% of their subjects had an A1c over 9%. This fact makes it unlikely that the overall result would apply to the US population with diabetes the average A1c in the U.S. is higher--closer to 9% than 7%.

But the linking of increased death risk with a major microvascular complication, kidney damage, suggest that those of us who strive to achieve extremely tight control--the so-called "5% Club" should rest easy.

An eleven year study of over 1800 people with diabetes found a straight line relationship between the risk of developing chronic kidney disease and the A1c. The risk began to increase significantly when the A1c rose over 6.0%.

Poor Glycemic Control in Diabetes and the Risk of Incident Chronic Kidney Disease Even in the Absence of Albuminuria and Retinopathy: Atherosclerosis Risk in Communities (ARIC) Study. Lori D. Bash et al. Arch Intern Med. Vol. 168 No. 22, Dec 8/22, 2008.

Preexisting heart disease was also a significant predictor of mortality in this study. This was defined as one of,
ischemic heart disease (IHD), International Classification of Diseases ninth revision (ICD-9), codes 410–414 and/or a history of coronary artery bypass surgery or percutaneous coronary intervention, cerebrovascular accidents [i.e. Stroke] including transient ischemic attacks (CVAs/TIAs) and/or peripheral vascular disease (PVD). PVD was defined as surgical intervention, history of claudication and/or absent pulsations of ankle or foot arteries (absence of pulsations of the dorsalis pedis arteries bilaterally was not scored as PVD when tibial posterior artery pulsations were present).
There is also a straight line relationship between A1c and heart disease in the non-diabetic population. You can read the details HERE. The salient feature is that the significant difference in heart attack risk takes place not when A1c is over 7% but when it moves from 4.7% to over 6%.

All in all, this is exceedingly good news. If even people with diabetes who maintain the abnormally high blood sugars that produce the 7% A1c have the same risk of death as people without diabetes, the fear that our diagnosis is a death sentence can be relaxed.

This also lays to rest the factoid repeated endlessly by doctors that a diabetes diagnosis is, health-wise, the same as having already had a heart attack. This study disproves that idea completely. Instead, this study suggests that having had a heart attack raises the likelihood of death but by the same amount in the diabetic and non-diabetic population, since the mortality in the two groups was the same.

Though the study found that within the diabetic population the A1c did not predict likelihood of death, we have to remind ourselves that the factors that did predict death in the diabetic population were those that increase in the general population as A1c goes over 6%.

A 7% A1c translates into an average blood sugar of 155 mg/dl. Since we know that keeping blood sugar under 140 mg/dl is the magic number for preventing neuropathy--which also appears to have been more frequent in the group who died--we can feel safe in believing that those of us who lower blood sugar to the 5% range without using drugs whose side effects are a higher risk of heart attack viz. Avandia, Actos, Glyburide, Amaryl, Prandin and Starlix, have done all we can to ensure we live long, happy, complication-free lives.

Before you leave this study, note the lack of relationship of cholesterol levels and mortality in this group. On average, all measures of cholesterol, as expressed as mean and standard deviation, were "better" in those who died. It is a shame that the study did not include the measurement of C-Reactive Protein, a measure of inflammation, as it would have been interesting to see how predictive it was in this group.



Ryan Lanham said...

Thanks, Jenny. I wish we had a whole set of studies like this...great stuff!

. said...

Dear Jenny, are you aware of this New Zealand study ( that links A1C and mortality? This is perhaps the largest study of this type and it confirms previous findings that A1C levels are strongly associated with subsequent mortality in people without a prior diabetes diagnosis. The study you refer didn't found a link between A1C and mortality, is this possible? Regarding "the lack of relationship of cholesterol levels and mortality", this is another evidence of the now almost dead lipid hypothesis. Please have a look at this article I wrote one week ago about cholesterol - - and also to Dr. Hyman's recent article at Regards, thanks for your blogging work!

Jenny said...

I am well aware of many studies that link A1c and mortality, but once people have A1cs of 7% or over, that relationship seems to weaken.

This latest study is only comparing A1c within the group of people with diabetes, if I understand it correctly. And in other studies the connection between A1c and mortality weakens once you cross over that 7% border.

It is between 4.7 and 6% that the major differences occur.

It's worth noting that many "normal" people have 6-7% A1cs which may partially explain the similarity in mortality in the study that is the subject of the blog.

OTOH, recent studies of people with diabetes that were looking at heart attack deaths had difficulty getting statistically significant results because of FAR LESS heart attacks happening than were predicted. It does look like diabetic-related heart attacks are most definitely on the decline.

Randeg said...

Excellent news that I have to spread around. It is about time we receive news like this although there were hints that life expectancy for the diabetics is just the same as that of the general population seeing that role models like Mary Tyler Moore and the newly confirmed judge of the Supreme Court are living a happy, full and long life.

Evelyn Guzman (If you want to visit, just click but if it doesn’t work, copy and paste it onto your browser.)

homertobias said...

Hi Jenny,

I was just wondering what you think of Dr. Ralph Defronzo's work, especially his Banting award lecture last year, the evil octette, and the efficacy of triple therapy in impaired glucose tolerence.
Thanks in advance for your consideration.

Anonymous said...

"Dear Jenny, are you aware of this New Zealand study ( that links A1C and mortality?"


Last time I looked for that one it still required a subscription.

So that's two new papers to read, where's my coffee?

Jenny said...

I had a look at that New Zealand study. I already document a lot of them on my main web site on the Heart Attack page.

The connection between A1c and neuropathy and microvascular complications is not all that strong. Post-meal blood sugar is MUCH better at prediction.

Personally I am not all that fond of the A1c because it works for groups, not individuals. There is a very wide variance among individuals in a way there is NOT with actual blood sugars.

People with low A1cs may have very high blood sugars if they have certain hemoglobin variants or anemia and get false senses of security. By the same token some people with perfect blood sugars get bad A1cs.

The A1c is entirely dependent on how normal the concentration of your hemoglobin is. Use blood sugar levels instead, and you'll be a lot better off.

Jenny said...

Re Dr. Defronzo I have read excellent articles written by him and have cited them on my site various places. My memory of that particular lecture was that it was still too close to the standard ADA line as far as treatment options goes. But it has been a while since I read it and I'm too fried right now to go look. I'm still getting over what may or may not be Swine flu. The doc is not all that helpful with the diagnosis.

Anonymous said...

Indeed, you've probably also seen the results in the various diabetes forums, where some people can predict their Aic accurately from spot readings while others run consistently high, or low. My A1c actually increased from 5.3 to 5.6 with better BG control, probably due to knocking out the near-hypo lows as well as the highs, and I've seen some nondiabetics also report higher than expected A1c.

So it can be an indicator but not definitive. It certainly makes hyperglycemia and hyperinsulinemia look like better markers than lipids though.