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.