Emily Oster

3 min Read Emily Oster

Emily Oster

Is Mastitis Linked to Breast Cancer?

Q&A on breastfeeding

Emily Oster

3 min Read

My mom had breast cancer at 40, and my best friend has breast cancer at 39. Both are their first in the family lineage to have it. They also both had mastitis in the same breast that has/had the cancer. I know that there is research that has shown a correlation in this. Why is it not discussed more with breastfeeding mothers? And if we know this, then why isn’t breastfeeding considered a risk factor, to allow for earlier preventative care?

—Breast ultrasounds for all!

I’m so sorry, first of all, to hear about your mom and your best friend. I hope they are doing as well as possible.

This is a complicated issue, because, on average, breastfeeding is associated with a decrease in breast cancer. It’s one of the better supported claims about the benefits of breastfeeding (more on that in this post). Yet there are correlational studies (like this one) that suggest that mastitis in particular is associated with a higher risk of breast cancer. 

baby breastfeeding
Wren Meinburg / Unsplash

However: in the best data we have, the link doesn’t appear to be causal. This paper uses data from 2.5 million women in Sweden. As is often true in papers with Scandinavian data, the data is detailed. Among the full population, the researchers found 8,411 diagnoses of mastitis, and of those, 106 women were ultimately diagnosed with breast cancer. When they compare this risk with the baseline risk among women without mastitis, they find about a 25% increase in the risk of cancer. 

This effect could be causal, but it could also reflect differences in other underlying risk factors. In this case, the authors have another way to learn about causality. The theory behind a link between mastitis and cancer is location-specific. If the link is causal, the breast cancer should be more likely to show up in the breast with the mastitis. The data here is detailed enough to look at that.

What the authors find is no systematic correlation between the mastitis side and the cancer side; it doesn’t look like the breast with mastitis is more likely to develop cancer. This strongly suggests that there is not a causal link, and the correlation we see reflects differences in other risk factors.

Even if mastitis isn’t causally linked to breast cancer, you could still argue that a history of mastitis might suggest a greater need for early screening, since mastitis might indicate other higher risk factors. In practice, the existing risk factors we use to determine screening are probably sufficient, since they capture the most important risk differences. 

(To be clear, breast ultrasound for all sounds great, but not because of this link.)

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Amanda
10 days ago

This was really interesting, thanks. I had not heard of this possible link before.

I think it is a little confusing to seem to recommend breast ultrasound for all. Ultrasound is only medically helpful for a small number of patients with specific circumstances. It’s used instead of mammograms in low income countries that can’t afford mammo machines, but it’s not recommended by doctors in the US as a primary screening modality, since we can afford mammograms, which are superior in general to ultrasound for breast imaging in most cases.

swoosh55cat
swoosh55cat
12 days ago

“…history of mastitis might suggest a greater need for early screening, since mastitis might indicate other higher risk factors.” What are some examples of risk factors here?

My mom was diagnosed with breast cancer at 76, and I’ve been prone to clogged ducts with both my babies and had mastitis with my first. Just trying to understand if we’re unclear of causality, what other risk factors should be be considering because this link?

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Gillian Goddard

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Milestones. We celebrate them in pregnancy, in parenting, and they’re a fun thing to celebrate at work too. Just a couple years ago I couldn’t have foreseen what this community would grow into. Today, there are over 400,000 of you here—asking questions, making others feel seen wherever they may be in their journey, and sharing information that supports data > panic. 

It has been a busy summer for the team at ParentData. I’d love to take a moment here to celebrate the 400k milestone. As I’ve said before, it’s more important than ever to put good data in the hands of parents. 

Share this post with a friend who could use a little more data, and a little less parenting overwhelm. 

📷 Me and my oldest, collaborating on “Expecting Better”

Milestones. We celebrate them in pregnancy, in parenting, and they’re a fun thing to celebrate at work too. Just a couple years ago I couldn’t have foreseen what this community would grow into. Today, there are over 400,000 of you here—asking questions, making others feel seen wherever they may be in their journey, and sharing information that supports data > panic.

It has been a busy summer for the team at ParentData. I’d love to take a moment here to celebrate the 400k milestone. As I’ve said before, it’s more important than ever to put good data in the hands of parents.

Share this post with a friend who could use a little more data, and a little less parenting overwhelm.

📷 Me and my oldest, collaborating on “Expecting Better”
...

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Comment “link” for an article with other tools to help you navigate risk and uncertainty.

#emilyoster #parentdata #riskmanagement #parentstruggles #parentingstruggles

I spend a lot of time talking people down after they read the latest panic headline. In most cases, these articles create an unnecessary amount of stress around pregnancy and parenting. This is my pro tip for understanding whether the risk presented is something you should really be worrying about.

Comment “link” for an article with other tools to help you navigate risk and uncertainty.

#emilyoster #parentdata #riskmanagement #parentstruggles #parentingstruggles
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Do any of these findings surprise you? Let us know in the comments!

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Dr. Gillian Goddard sums up what she learned from the Hot Flash S e x Survey! Here are some key data takeaways:

🌶️ Among respondents, the most common s e x u a l frequency was 1 to 2 times per month, followed closely by 1 to 2 times per week
🌶️ 37% have found their sweet spot and are happy with the frequency of s e x they are having
🌶️ About 64% of respondents were very or somewhat satisfied with the quality of the s e x they are having

Do any of these findings surprise you? Let us know in the comments!

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Here’s what we know from a data standpoint:
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✈️ A JAMA Pediatrics paper estimates about 0.4 child air crash deaths per year might be prevented in the U.S. with car seats
✈️ Cars are far more dangerous than airplanes! The same JAMA paper suggests that if 5% to 10% of families switched to driving, then we would expect more total deaths as a result of this policy.

If you want to buy a seat for your lap infant, or bring a car seat for an older child, by all means do so! But the additional protection based on the numbers is extremely small.

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This graph shows sleeping location by age. You’ll notice that for the first three months, most kids are in their own sleeping location in a parent’s room. Then, over the first year, this switches toward their own room. As kids age, sharing a room with a sibling becomes more common.

Head to the newsletter for more and stay tuned for part two next week on naps! 🌙

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Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster

Weekends are good for extra cups of ☕️ and listening to podcasts. I asked our team how they pod—most people said on walks or during chores. What about you?

Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster
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#parentdata #emilyoster #tickseason #bugbites #bugspray

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Prevention is key! I suggest:
⭐ Regular tick checks
⭐ Using bug sprays with DEET
⭐ Wearing long sleeves and pants in the woods

Some parents worry about DEET, but repellants with up to 30% DEET are recommended by both the CDC and AAP. The data says you’re in the clear, so go for it. Enjoy your summer!

#parentdata #emilyoster #tickseason #bugbites #bugspray
...