Nocturne
Well-known member
I've recently been doing some more reading and figuring on CAC scores, and I've come to the conclusion that there may be a bit of wowsering and fear-mongering coming from some circles.
I'm not saying that the CAC score is an invalid measure of CHD risk or anything -- far from it! But a couple of things have made me think in the last day or so, and I'm going to share them here.
First, this:
http://www.ajronline.org/doi/pdf/10.....181.3.1810743
This is a fairly old paper from 2003 discussing the use of CAC scores to stratify risk in patients. Nothing particularly new here, except I noticed some of the graphs that are located down just a bit where they plot average CAC score by age and percentile rank. If you scroll down a bit, you'll find them. When I saw them, it struck me that it appeared that CAC grew rather quickly early on but growth seemed to taper off as score and/or age rose. You can clearly see this with every percentile rank -- so it's not just a matter of the top 1% showing "less growth" where that could potentially be confounded by people simply dying of heart disease once their CAC scores got above a certain threshold.
Today, I went to the MESA website and closely examined their data for CAC scores by age and percentile rank. You can find the website here:
https://www.mesa-nhlbi.org/Calcium/input.aspx
I wrote down and made a rough graph of my own for CAC score by age and percentile rank for caucasian men. Then I calculated yearly percentage growth of CAC for ten year spans of time from ages 45-55, 55-65, 65-75, and 75-84 (the MESA data does not go above age 84).
What I found was very interesting. It would seem that across percentile ranks, CAC growth rate (in the form of percent growth per year) DOES slow down as scores and age get higher. Again, this is true across percentile ranks, so it's not just a matter of this being an illusion caused by people at the top of the range dying off when their scores get above a certain point.
We've all heard the statistics about CAC growing at "an average of 20% per year," or "up to 30% per year," and similar scary information. And this analysis (which you can do for yourself with the MESA data if you have the time) reveals these statements to be true -- for certain age groups and percentile ranks. Between the ages of 55 and 65, caucasian men in the 50th percentile rank for CAC do indeed see a rise in CAC of 27% per year. But this shifts to an average of only 13% per year between the ages of 65-75, and slows down again to 9% per year between the ages of 75-84.
It's impossible to calculate growth for the bottom 25% of the caucasian male cohort's range until they reach 65, as they have no measurable CAC until just before this point, but between 65 and 75 they show an average growth of 26% per year, which slows to 12% per year between the ages of 75 and 84.
At the 75th percentile, there is growth of a whopping 53% per year from the age of 45-55, but this again slows to 17% per year from 55-65, 10% per year from 65-75, and 7% per year from 75-84.
And at the 90th percentile rank, CAC growth is 21% per year on average from 45-55, 13% per year from 55-65, 10% per year from 65-75, and only 6.5% per year from 75-84.
I even ran the numbers for the top 99th percentile rank, which is sadly where I am at, and found growth of 13% per year from the ages 45-55, 13% per year from 55-65, 9% per year from 65-75, and 3.5% per year from 75-84 -- although I am sure that at this far end of the bell curve, there MUST be at least some confounding of the data by people simply dying off at ultra-high CAC scores and causing people with lower scores to become the "new top 1%".
What does this mean?
Well, consider a caucasian man of 55 who learns that his CAC score is a whopping 234 (placing him at the 90th percentile rank for caucasian men of his age). He does some reading and learns that typical CAC growth is 20% per year, and that a score of 1000 is considered "crazy-go-nuts high". He whips out his calculator to learn with horror that at a normal growth rate his score will be 1448 by age 65, 8970 by age 75, and an impossible 55,546 by age 85. He concludes that he'll never live to see 85, and will probably be dead by his late 60s -- if he's LUCKY!
But that's not necessarily true, even if his progression is simply average from then on in. In reality, his CAC score will likely be about 802 by age 65, 2030 by age 75, and 3848 by age 84.
Now those ARE terrible scores, and he'd be best off doing whatever he can to slow down CAC growth as much as he can -- but he isn't doomed to die young, even if he has typical CAC progression.
Now for me, personally, in the top 1% bracket -- it's still pretty damned ugly, but not as ugly as it might seem at first. If I progress at about 20% per year until age 45, I'll be about 260 by then, and then the average progression rates from that point on would put me at 913 by age 55, 3099 by age 65, and 7336 by age 75. If I somehow lived to 84, I'd be pushing 10,000 -- what I consider "critical mass" because we never hear of anyone actually reaching that point, and because the MESA data doesn't go above 9999. So I have EVERY reason to try to slow my CAC growth by as much as possible! But even if I can't, and I progress at the "average" rates -- I don't hit "critical mass" at 65 or so, like a flat 20% per year progression would have me do.
This information is important to the average Joe, who may factor at age 55, CAC score 10, and progression rate of 27% on a repeat scan that he's doomed to have a score of 7800 by age 85 and no hope of ever seeing 90. That's not the case at all. He should still take steps to improve his health and his odds, but he can relax a bit and let go of some unhealthy anxiety.
I'm not saying that the CAC score is an invalid measure of CHD risk or anything -- far from it! But a couple of things have made me think in the last day or so, and I'm going to share them here.
First, this:
http://www.ajronline.org/doi/pdf/10.....181.3.1810743
This is a fairly old paper from 2003 discussing the use of CAC scores to stratify risk in patients. Nothing particularly new here, except I noticed some of the graphs that are located down just a bit where they plot average CAC score by age and percentile rank. If you scroll down a bit, you'll find them. When I saw them, it struck me that it appeared that CAC grew rather quickly early on but growth seemed to taper off as score and/or age rose. You can clearly see this with every percentile rank -- so it's not just a matter of the top 1% showing "less growth" where that could potentially be confounded by people simply dying of heart disease once their CAC scores got above a certain threshold.
Today, I went to the MESA website and closely examined their data for CAC scores by age and percentile rank. You can find the website here:
https://www.mesa-nhlbi.org/Calcium/input.aspx
I wrote down and made a rough graph of my own for CAC score by age and percentile rank for caucasian men. Then I calculated yearly percentage growth of CAC for ten year spans of time from ages 45-55, 55-65, 65-75, and 75-84 (the MESA data does not go above age 84).
What I found was very interesting. It would seem that across percentile ranks, CAC growth rate (in the form of percent growth per year) DOES slow down as scores and age get higher. Again, this is true across percentile ranks, so it's not just a matter of this being an illusion caused by people at the top of the range dying off when their scores get above a certain point.
We've all heard the statistics about CAC growing at "an average of 20% per year," or "up to 30% per year," and similar scary information. And this analysis (which you can do for yourself with the MESA data if you have the time) reveals these statements to be true -- for certain age groups and percentile ranks. Between the ages of 55 and 65, caucasian men in the 50th percentile rank for CAC do indeed see a rise in CAC of 27% per year. But this shifts to an average of only 13% per year between the ages of 65-75, and slows down again to 9% per year between the ages of 75-84.
It's impossible to calculate growth for the bottom 25% of the caucasian male cohort's range until they reach 65, as they have no measurable CAC until just before this point, but between 65 and 75 they show an average growth of 26% per year, which slows to 12% per year between the ages of 75 and 84.
At the 75th percentile, there is growth of a whopping 53% per year from the age of 45-55, but this again slows to 17% per year from 55-65, 10% per year from 65-75, and 7% per year from 75-84.
And at the 90th percentile rank, CAC growth is 21% per year on average from 45-55, 13% per year from 55-65, 10% per year from 65-75, and only 6.5% per year from 75-84.
I even ran the numbers for the top 99th percentile rank, which is sadly where I am at, and found growth of 13% per year from the ages 45-55, 13% per year from 55-65, 9% per year from 65-75, and 3.5% per year from 75-84 -- although I am sure that at this far end of the bell curve, there MUST be at least some confounding of the data by people simply dying off at ultra-high CAC scores and causing people with lower scores to become the "new top 1%".
What does this mean?
Well, consider a caucasian man of 55 who learns that his CAC score is a whopping 234 (placing him at the 90th percentile rank for caucasian men of his age). He does some reading and learns that typical CAC growth is 20% per year, and that a score of 1000 is considered "crazy-go-nuts high". He whips out his calculator to learn with horror that at a normal growth rate his score will be 1448 by age 65, 8970 by age 75, and an impossible 55,546 by age 85. He concludes that he'll never live to see 85, and will probably be dead by his late 60s -- if he's LUCKY!
But that's not necessarily true, even if his progression is simply average from then on in. In reality, his CAC score will likely be about 802 by age 65, 2030 by age 75, and 3848 by age 84.
Now those ARE terrible scores, and he'd be best off doing whatever he can to slow down CAC growth as much as he can -- but he isn't doomed to die young, even if he has typical CAC progression.
Now for me, personally, in the top 1% bracket -- it's still pretty damned ugly, but not as ugly as it might seem at first. If I progress at about 20% per year until age 45, I'll be about 260 by then, and then the average progression rates from that point on would put me at 913 by age 55, 3099 by age 65, and 7336 by age 75. If I somehow lived to 84, I'd be pushing 10,000 -- what I consider "critical mass" because we never hear of anyone actually reaching that point, and because the MESA data doesn't go above 9999. So I have EVERY reason to try to slow my CAC growth by as much as possible! But even if I can't, and I progress at the "average" rates -- I don't hit "critical mass" at 65 or so, like a flat 20% per year progression would have me do.
This information is important to the average Joe, who may factor at age 55, CAC score 10, and progression rate of 27% on a repeat scan that he's doomed to have a score of 7800 by age 85 and no hope of ever seeing 90. That's not the case at all. He should still take steps to improve his health and his odds, but he can relax a bit and let go of some unhealthy anxiety.
