With this post, we’ll explore bolus and continuous infusion basal information from people who have donated their diabetes data through the Tidepool Big Data Donation Project. Here’s a quick summary of our findings:
In our last analysis, we looked at average CGM levels across different age groups. This time, we look at insulin pump use.
The dataset analyzed contains over 479 years (175,000+ days!) of insulin pump data from 803 donors. All of the results come from data that has both bolus and continuous infusion basal information. The representation of insulin pumps is spread across Tandem (282), Omnipod (217), Medtronic (210), and Animas (94). We will not be comparing across brands.
For this analysis, we've excluded data from donors who are using a closed-loop system. For more details on how we conducted this analysis, see the technical notes section at the end of this post. Here is an overview of the data:
As is always the case with these conversations, please keep in mind that your diabetes will vary from what you see here. You may require more or less insulin than the medians we present, and that’s cool. The point of this analysis is to see what we can learn from each other.
Total Daily Dose of Insulin includes all the boluses (that is, insulin for food and blood glucose corrections), as well as all basal insulin delivered. Said simply, it’s how much insulin each person got from their pump each day. Here we’re showing the median (or 50th percentile) daily dose for each age group to get a sense of the general trends.
For the data nerds reading this blog post, below is the distribution of the total amount of insulin per day. Just like the Trends view in the Tidepool web app, we are showing the median (the colored square in the middle of each bar), the distribution of 50% of the data (25th to 75th percentile) in dark gray, and the distribution of 80% of the data (10th to 90th percentile) in light gray. One thing to note: we’ve removed the outliers (the top and bottom 10%) to make the graphs a little easier to read.
We see that the total amount of insulin given each day is highly variable. As expected, children are using less insulin than our older groups, with a general trend of insulin needs increasing until age 18, where the amounts start to level off. We'll revisit this trend shortly.
As you may know, there are a few key settings on an insulin pump:
These three settings work together along with the blood glucose readings and any carb counts you enter to determine how much insulin you need at a given point in time.
So how do the insulin-to-carb ratios vary by age?
The first thing to note about insulin-to-carb ratios is that they are highly variable at the younger ages, and decrease until age 12 or so, where they begin to level off. It may be important to note that very young children, in addition to having low insulin-to-carb ratios, may also be using diluted insulin, which this data does not capture. (Side note: We think it's silly to call this "insulin to carb" ratio, when it's really "carbs to insulin ratio", but that's what everyone does, so we will too…)
We see a similar trend for insulin sensitivity (a.k.a. correction factor), which represents the expected blood glucose drop for 1 unit of insulin:
You can view this chart in mmol/L here.
You can view this distribution chart in mmol/L here.
Let’s walk through what we’ve learned from your food and correction boluses. Remarkably, it’s rather surprising — or boring depending on how you look at it — to see how uniform much of the bolus analysis appears across all age groups. The median number of daily boluses, regardless of type (normal, dual, extended), is consistently 6-7 per day. Remember, the dataset we analyzed is limited to people on insulin pumps. We might assume people using insulin pens bolus less often, but we don’t have the data to prove it. Yet.
Here’s a look at variability of total number boluses per day, across all age groups.
Based on the carb values that you all put into your insulin pumps, we were able to calculate the total number of carbs you eat per day.
There’s a significant increase in carbs around the ages of puberty, and a general trend of the median number of daily carbs decreasing with age. However, the number of carbs per day really varies, especially when you look at the distribution of the data.
We also analyzed the number of carbs given per bolus to see how much food you’re covering with each bolus when carbs are entered into the bolus calculator. Here we see a trend of the number of carbs per meal bolus increasing until age 12-14, remaining around 40g per meal until age 21-24, and then dropping to around 30-32g thereafter.
Here’s the distribution of carbs per meal bolus.
Here’s a look at median basal rate of insulin delivered per hour for each age group. For this analysis we included both scheduled and temporary basals to get a sense of the actual amount of basal insulin given per hour. In addition, we weighted the basal rate by basal rate duration, so the median here is actual a weighted median. See the technical notes for details on that one.
Oh, and if you are curious to know how the median values change when you only look at the scheduled basal rates… well, they don’t! The only change in in the 18-20 year old group. The median value jumps from 0.75 to 0.80 U/hr.
We can also look at the distribution of basal rates. Again, we see a noticeable leap once puberty gets added to the mix, but by and large, the basal rate levels out by the time you reach your 20s.
Finally, here’s a look at the weighted median basal rate duration. For this analysis, we only consider scheduled basal rates and durations.
Most people run their basals for 4-6 hours, which means your active basal profiles have about 4 to 6 basal rates. Though, we do see a lot of variance across all age groups.
After all this discussion about and around your basal and bolus data, where does that leave us? Does it all balance out in the end? Well, that depends on your age!
Here’s a look at the typical amount of basal (top) and bolus (bottom) insulin delivered per day. As we noted in the beginning, insulin amounts increase with age and then plateau around age 18-20.
And, keeping with the other theme in this blog post...there is much variation! In this case, the amount of variation increases with age and levels off around 18 or so.
Many conversations in clinic around insulin usage are informed by the basal:bolus ratio. Some endocrinologists and diabetes educators like you to aim for a 50/50 split, though others prefer less basal and more aggressive meal bolusing. We don’t know of a consensus statement on this, and remember, your diabetes may vary.
This chart shows the median percent of insulin delivery that came from your basals by age group. Like the trend we saw with basal rates, the median basal:bolus ratios increase until age 20 (from around 35:65 to 50:50), and then level off close to 50:50 thereafter.
As we discussed in our previous analysis, there’s always bias to consider. For the datasets analyzed and presented in this post:
What do you think about the results of our analysis? What other questions would you like us to explore? Leave a comment or send an email to bigdata@tidepool.org and let us know what you think!
Be sure to check out this guide if you’d like to donate your own diabetes data to the Tidepool Big Data Donation Project.
Yours in big data,
Ed, Brandon, and Christopher
If you think your company would benefit from collaborating with Tidepool to better understand the needs of people with diabetes, contact us at bigdata@tidepool.org.
If you are a citizen scientist or academic researcher and need real device data to help with your project, you can also email us at bigdata@tidepool.org. We’re working a program to make datasets available for free or at greatly reduced cost.
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