A major Canadian study published in 2024 found that breast cancer diagnoses in women in their 20s have gone up by 45.5% over the past 35 years. Women in their 30s saw a 12.5% increase. Their 40s, 9.1%. This wasn't some small, easy-to-dismiss study — it was led by Dr. Jean Seely at the University of Ottawa and published in a peer-reviewed journal. The numbers are real, and they're hard to ignore.
So what's going on?
There's no single villain here. But a few things keep coming up in the research and some of them might surprise you.
It comes down a lot to hormones. The longer your body is exposed to estrogen and progesterone over your lifetime, the higher your risk tends to be. And that window has been getting longer for women over the past few generations. Girls are getting their first periods earlier, people are having kids later or not at all and breastfeeding rates have declined. Each of these things adds up. Research suggests that even a single year's difference in when you get your first period can shift your risk by around 9–10%.
Alcohol is more of a factor than most people realize. Alcohol raises estrogen levels in the body and even moderate, regular drinking is linked to increased breast cancer risk.
Everyday chemicals are worth paying attention to. Endocrine-disrupting chemicals found in scented products, plastic containers and a lot of everyday items can interfere with your body's hormone systems. The research is still developing, but given how hormone-driven breast cancer is, scientists are taking this seriously.
Genetics play a role for some women. About 12% of young women diagnosed with breast cancer carry a BRCA1 or BRCA2 mutation. If breast or ovarian cancer shows up in your family history (especially in close relatives or at a young age) that's a conversation worth having with your doctor sooner rather than later.
Detecting Early
Breast cancer in younger women tends to be more aggressive. The subtypes that show up more often in women under 40 — triple-negative and HER2-positive — are harder to treat. Since women aren't routinely screened, these cancers often get caught later, when they're harder to treat.
Women under 40 at diagnosis are nearly 40% more likely to die from breast cancer than older women. A huge part of that comes down to late detection.
Which means the most powerful thing you can do right now isn't complicated. It's just about paying attention.
How to Be Proactive
Get to know your own breasts. This sounds almost too simple, but it genuinely matters. You can't notice a change if you don't know what's normal for you. You don't need to follow some rigid monthly ritual, just check in with yourself regularly. In the shower, in front of the mirror, lying down. You're looking for lumps, thickening, skin changes, nipple changes, or anything that just feels new or different. If something feels off, get it looked at.
Know your family history. Do you actually know if breast or ovarian cancer runs in your family? If a parent, sibling, or child has been diagnosed — especially young — tell your doctor. You may qualify for earlier screening or genetic testing, and that information can genuinely change what care you have access to.
Start the screening conversation at 40. Canadian provincial guidelines vary wildly, and many don't fund mammograms until 50. But Breast Cancer Canada recommends talking to your doctor about screening when you turn 40 and earlier if you have risk factors.
Take an honest look at your drinking. If you're a regular drinker, even casually, it's worth factoring into your thinking. Cutting back is one of the more straightforward ways to lower your risk, even if it's not the easiest one to hear.
Reduce your exposure to hormone-disrupting chemicals where you can. You don't have to throw out everything you own. But switching to fragrance-free products, not heating food in plastic containers and filtering your drinking water are small, manageable changes that can add up over time.
Move your body consistently. Nothing extreme but regular, moderate exercise helps regulate hormones and lower inflammation, both of which matter when it comes to breast cancer risk.
Conclusion
The rise in breast cancer among younger women is real, it's happening in Canada and we don't fully understand it yet. What we do know is that a lot of it connects back to hormonal health which means the more you understand your own body, the better equipped you are.