# I don't understand the math of diabetes and pre-diabetes **URL:** \ **Category:** Factual Questions\ **Created:** [October 9, 2013, 10:07pm UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821 "2013-10-09T22:07:43Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [October 9, 2013, 10:07pm UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/1 "2013-10-09T22:07:43Z")
I understand certain glucose and A1C readings indicate pre-diabetes vs diabetes. However I have read stats like ‘within 3-5 years, 25% of people with pre-diabetes develop diabetes’, or that after 10 years over half of people with pre-diabetes have diabetes. But in the US about 35% of adults over 20 have pre-diabetes (almost 80 million), while only about 11% of people age 20+ have diabetes. In China the stats are something like 12% are diabetic but 50% are pre-diabetic. I’m sure genetic factors and lifestyle play a huge role in how long before pre-diabetes becomes diabetes (if ever). But how do you get stats like 'half will develop diabetes in 10ish years) when the number of prediabetics is triple the number of diabetics? if that were true, then there would be 40 million new diabetics in 10 years, tripling the US diabetic population. Even the ‘within 3-5 years 25% with pre-diabetes will develop diabetes’ means that there will be 20 million new diabetics within 3-5 years, doubling the number in the US. That doesn’t sound right. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [October 9, 2013, 11:22pm UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/2 "2013-10-09T23:22:16Z")
Ten years ago there weren’t as many prediabetics. Ten years from now there will be half again as many diabetics as there are now. (3x prediabetics/2) That’s assuming the trend continues. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [October 9, 2013, 11:33pm UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/3 "2013-10-09T23:33:27Z")
> [@Yllaria](#): > > Ten years ago there weren’t as many prediabetics. Ten years from now there will be half again as many diabetics as there are now. (3x prediabetics/2) > > That’s assuming the trend continues. How will there be half as many diabetics in 10 years? Did you mean prediabetics? The info I’ve read implies there will be an additional 40+ million diabetics in 10 years, tripling the number of diabetics in the US (assuming none of the 20 million current diabetics die, which isn’t likely but the majority should be alive in 10 years). [This chart](http://www.cdc.gov/diabetes/statistics/prev/national/figpersons.htm) has the rates of diagnosed diabetes growing drastically from about 6 million in the mid 80s, to 12 million in 2000 to 22 million today. But there are several trends that would explain that 1. The diagnosis of diabetes is lower now, it used to be fasting glucose of 140, now it is 126. That added millions of people. 2. More people are diagnosed compared to in the past (due to things like awareness, cheaper/more prevalent testing, etc) 3. The US population has grown by 30% since the 80s. 4. We are older than we were as a nation than in the past, and diabetes gets worse with age. 5. We are a less white, more latino/black nation than in the past and blacks/latinos get diabetes at higher rates. All in all, if that number jumps from 20 million to 60 million in 10 years that would be completely out of the current trends, seeing how the number only went from 13 million to 21 million from 2001-2011. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [October 10, 2013, 4:41am UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/4 "2013-10-10T04:41:34Z")
(S)he said “half again.” 1.5 times. 50% more. Not half as many. Which is probably an underestimate. Increasing numbers of new prediabetics will be (and likely has been) a leading indicator for increasing numbers of diabetics years down the road. Hence in ten years there will be an additional 40 million (minus those who currently have diabetes but have died) diabetics added to the roughly 25 million now labelled. Ten years ago there were likely fairly few prediabetics relative to today’s numbers. Funny you do not mention that we are much fatter and less fit and at earlier ages than we were before too. The other points are valid but the tightest correlation is with obesity rates. Also note that case finding and identification of pre-diabetics has improved as well. As has the definition. Not sure if your cited numbers use the older or the newer definition of prediabetes aka impaired fasting glucose or IFG. One study that these rates come from is [this one](http://care.diabetesjournals.org/content/30/2/228.full). > [@](#): > > In this retrospective cohort study of real-world patients with incident IFG, we found that 8.1% who met the added portion of the ADA’s 2003 criterion for IFG (100–109 mg/dl) progressed to diabetes over a mean follow-up of 6.3 years, an annual rate of 1.34%. Among subjects with incident IFG under the old ADA definition (110–125 mg/dl), we observed an annual rate of progression to diabetes of 5.56%. This rate of progression is lower than rates reported by all but one previous study of subjects enrolled at unknown times after IFG had already begun (3,5–8). The progression rate from the old IFG cut point that we observed is very similar to the rate reported by Meigs et al. (9), which is the only previous study that has estimated progression from the time IFG first appeared. This confirms the importance of accounting for time since IFG onset when predicting the risk of diabetes and likely explains much of the wide variation among earlier studies. > > Three times the proportion of subjects with original IFG progressed to diabetes than added IFG subjects, and they did so more rapidly, at over four times the rate. Among added IFG subjects, progression to original IFG increased the risk of ultimately developing diabetes by threefold. Once original IFG was reached, initially added IFG subjects developed diabetes at approximately the same rate as patients who started from original IFG. Only about one-third of subjects who developed diabetes did so without first passing through original IFG. Moreover, the rate of diabetes incidence among all subjects (i.e., the rate for the ADA’s new IFG definition) was 1.95% per year, which is less than half the 5.56% rate observed for the old IFG definition. … In our data, higher BMI and lower HDL cholesterol were the most highly significant nonglucose predictors of hyperglycemic progression … A [similar result](http://care.diabetesjournals.org/content/32/4/606.full) in a European population using the oral glucose tolerance test as the measure for prediabetes. Note we are also seeing increasing numbers of both prediabetes and T2 diabetes in kids. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [October 10, 2013, 4:51am UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/5 "2013-10-10T04:51:50Z")
For those playing along at home. Ignore the last sentence, since that’s what the smart dudes here are talking about… Impaired fasting glucose (IFG), more commonly known as pre-diabetes refers to a condition in which the fasting blood glucose level is consistently elevated above what is considered normal levels; however, it is not high enough to be diagnosed as diabetes mellitus.[1] This pre-diabetic state is associated with insulin resistance and increased risk of cardiovascular pathology, although of lesser risk than impaired glucose tolerance (IGT). IFG can progress to type 2 diabetes mellitus if lifestyle changes are not made. There is a 50% risk over 10 years of progressing to overt diabetes. A recent study cited the average time for progression as less than three years.[2] [Wiki cite.](https://en.wikipedia.org/wiki/Impaired_fasting_glucose) ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [October 10, 2013, 9:48pm UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/6 "2013-10-10T21:48:29Z")
I found this article from 2004. [http://archive.hhs.gov/news/press/2004pres/20040429.html](http://archive.hhs.gov/news/press/2004pres/20040429.html) > [@](#): > > “Pre-diabetes” – a condition that raises a person’s risk of developing type 2 diabetes, heart disease, and stroke – is far more common in America than previously believed, according to a new HHS estimate released today. About 40 percent of U.S. adults ages 40 to 74 – or 41 million people – currently have the condition, which is marked by blood glucose levels that are higher than normal but not yet diabetic. Many people with pre-diabetes go on to develop type 2 diabetes within 10 years. So if 9 years ago about 40% of people age 40-74 had prediabetes, shouldn’t half of them be diabetic by now? This is just people 40-74, not people 20-39 or 75+ which would likely add another 10-20 million people to the ranks of prediabetics in 2004. If true, we should’ve added 20-30 million diabetics by now. But the rates have gone up by about 10 million and part of that is just better diagnosis (people who have it know they have it) and population growth. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [October 11, 2013, 1:48am UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/7 "2013-10-11T01:48:03Z")
Here is another thing. I haven’t read most of the article associated with this image. [http://www.drhuhc.org/articles/images/fig2.1\_distNormPreDiabeticAndDiabeticPtsByAge.jpg](http://www.drhuhc.org/articles/images/fig2.1_distNormPreDiabeticAndDiabeticPtsByAge.jpg) But it shows rates of normal glucose, pre-diabetes and diabetes by age bracket. I do not see the rates of new diabetes ever being anywhere near half the rates of prediabetes among people a decade younger. Example, among 40-49 year olds the rates of pre-diabetes are 42% with diabetes rates of 9-10%, among 50-59% the rates of diabetes are 13%. So the rate of diabetes only went up about 3-4% among people 10 years older despite 42% of people being prediabetic in their 40s. They aren’t the same people, but the rates of diabetes should be higher according to that, rates of pre-diabetes are 30-50% after the 30s, but even by a person’s 70s the rates of diabetes only tops out at about 30% and is only about 15% in the 50s. It makes no sense. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [October 11, 2013, 2:26pm UTC](https://boards.straightdope.com/t/i-dont-understand-the-math-of-diabetes-and-pre-diabetes/670821/8 "2013-10-11T14:26:25Z")
A couple of comments Wesley - 1. The flaw in the repeated cite of “that after 10 years over half of people with pre-diabetes have diabetes” is evident in the cite I gave you. It is possibly true for the older, pre-2003, definition of prediabetes, fast blood glucose of 110 to 125. For that definition the annual rate was 5.56% of prediabetics becoming diabetics. Do the math and it comes to roughly about half becoming diabetic in 10 years. But the definition _changed_ in 2003 to also include those with a fasting glucose of 100 to 109. Suddenly _lots_ more people are prediabetic, and indeed they are at increased risk to become diabetic, but not at as much increased risk. For all included in the new definition the annual rate of becoming diabetic was under 2%. That 2004 estimate used the new to 2003 definition which includes many in the 100 to 109 group; that 40% of the population 40 to 74 is at about a 2% annual risk, not a nearly 6% annual risk. The numbers that were prediabetic by the pre-2003 impaired fasting glucose definition were, in those 45 to 74 and overweight, [in 2000](http://care.diabetesjournals.org/content/26/3/645.full.pdf+html), 11.9%, up to 22.6% adding in those who had abnormal oral glucose challenge with normal fasting glucose. Half of that 12% probably became diabetic over the next 10 years, other than those who changed lifestyles, or died. 2. Those aged 40 to 74 who became diabetic are also at greater risk to have died off over the next years than those who did not and not be found in the living diabetic group. 3. Those original “half will become diabetic” numbers also were based without intervention. With identification and with consequent changes in nutrition and exercise habits the numbers can be impacted dramatically. That is increasingly occurring. 4. [This article](http://care.diabetesjournals.org/content/32/2/287.full.pdf+html) also may be of interest. My impression before your question inspired me to look for it was that was a true rise in prediabetes using the same definition of the term but such may actually not be the case. Which shocks me. Bottom lines: > [@](#): > > The crude prevalence of diagnosed diabetes in individuals aged ≥20 years rose significantly from 5.1% in 1988–1994 to 7.7% in 2005–2006 … There were no significant changes between the surveys in prevalence of undiagnosed diabetes … There was no substantial change in prevalence of IFG or IGT between 1988–1994 and 2005–2006. Likewise, total pre-diabetes (IFG or IGT) did not change significantly except in Mexican Americans (aged 40–74 years standardized 41.7 to 33.1%; P = 0.03). The combined total prevalence of diabetes and pre-diabetes increased significantly between the surveys only in non-Hispanic blacks … > > … hese recent data indicate that 12.9% of the adult U.S. population aged ≥20 years have diabetes (7.7% previously diagnosed and 5.1% undiagnosed), of which 39.8% is undiagnosed. Another 29.5% of the population is at risk of diabetes based on having pre-diabetes (IFG or IGT). Overall, approximately 40% of the U.S. population has some hyperglycemic condition. The elderly population is particularly susceptible, with about one-third having diagnosed or undiagnosed diabetes and three-quarters having diabetes or pre-diabetes. Minority groups continue to suffer disproportionately, as prevalence of diagnosed and undiagnosed diabetes combined is 70–80% higher in non-Hispanic blacks and Mexican Americans than in non-Hispanic white subjects. But whereas diagnosed diabetes has risen significantly over the last 10–15 years, particularly in non-Hispanic blacks, undiagnosed diabetes as a proportion of total diabetes has remained relatively stable and may be decreasing, particularly in Mexican Americans. … > > … Thus, whereas diagnosed and total diabetes and total hyperglycemic conditions remain disproportionately high in minority groups, it may be that diabetes is being diagnosed more frequently in these groups, both over time and relative to non-Hispanic whites. This was also found when comparing data from 1999–2002 with those from 1988–1994 (3). More focused screening may be occurring in these groups (19). Decreases over the past several decades in the proportion of diabetes that is undiagnosed have occurred only among the most obese (20). We also found that pre-diabetes decreased significantly over time in Mexican Americans. > > Overall, almost 30% of the population had pre-diabetes (IFG or IGT), a condition that increases the risk for diabetes and is associated with other cardiovascular risk factors (4,8). … It is encouraging that prevalence of pre-diabetes did not appear to increase between the surveys; this is surprising given the increase in diagnosed diabetes and obesity (10) over time. … \*\*For the too long did not reads: In those who meet the old pre-2003 definition of prediabetes half will likely become diabetic unless they change lifestyle or die first. Many fewer under the current broader definition and less if they do something about it.\*\*