Science Friday - Study Shows Which Kids Are Getting Periods Younger Than Others

Episode Date: July 2, 2024

If you have teenagers in your life, you may have noticed that kids these days seem to be getting their periods earlier than previous generations did. It’s not just in your head: A recent study from Harvard’s T.H. Chan School of Public Health confirms what many people have assumed, as well as additional findings about period regularity in younger generations.The study, which analyzed self-reported data from more than 71,000 participants in the US, found that menstrual periods are arriving earlier for younger generations, with the average age dropping from 12.5 years old for people born in 1950 to 11.9 years old for those born in 2005. More staggering, however, is that both early menarche—a person’s first menstrual period—and irregular periods were much more common in the non-white and low-income study participants. And period irregularity has become more common for younger generations compared to their older counterparts.These findings are a big deal, because early menarche and irregular periods can be a signal of future health issues, including pregnancy complications and mental health changes. Joining guest host Anna Rothschild to discuss the findings and their implications is lead study author Dr. Zifan Wang, postdoctoral research fellow at Harvard University in Cambridge, Massachusetts.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Today's kids are getting their periods earlier than previous generations. The trends that we're seeing are a bit concerning since it's really heavily connected to later life health conditions. It's Tuesday, July 2nd, and of course, today is Science Friday. I'm SciFRI producer Kathleen Davis. It's been a noted trend in recent years that kids aren't just getting their periods earlier. Those periods are less regular than in years past. too. A new study finds these differences are most noticeable for kids who are low income and not white. There's an urgency to find out why this is, because these can be a sign of future health issues into adulthood.

Guest host Anna Rothschild speaks with lead author Zee Fon Wong about the study. Welcome to Science Friday. Hi, thank you for having me. So let's start with your findings from this study. Can you just explain what you found? Yeah, sure. So we looked at individuals within the U.S. who were born between 1950 to 2005, and we found that younger generations tend to start their first period, or what we call, manarche, at a younger age. So on average, that's from like 12.5 years old for those who were born in the 1950s, all the way down to 11.9 years old among those who were born around 2,000.5 years old,

among those who were born around 2005. And we also saw that the rate of early monarchy, which is defined as first period before 11 years old, has also doubled over the years from 9% to about 16%. One other thing that we did found very interesting is another marker for menstrual health, which is the time it takes for someone to establish regular menstrual cycle since their first period.

This time is also becoming long. for younger generations. And just as you mentioned, we also saw these trends to be more heavily impacting people of color, including black, Hispanic, and Asian individuals when compared to their white peers. Why is it important to track irregular periods specifically? So in other literature, researchers have found that either early menarche or irregular periods to be correlated with disease later in life, such as cardiovascular. superior disease, certain types of cancer as well as infertility. So the trends that we're seeing

in terms of declining age and monarchy as well as increasing menstrual cycle irregularity are a bit concerning due to that reason, since it's really heavily connected to later life health conditions. You talked about how, you know, this study is looking at a wide range of people, people born between 1950 and 2005. Can you explain a little bit how you collect? the data for this study? Yes, absolutely. So our analysis used self-reported data from surveys among participants from the Apple Women's Health Study, which is a U.S.-based digital cohort study. This study is a collaboration between Harvard, Apple, and the National Institute of Environmental Health Sciences. And those who were included in our analysis met the city

eligibility criteria of having an iPhone. being at the age of consent, living in the U.S., and have menstruated at least once in their life. And we analyzed these trends based on participants' self-reported age and monarchy, as well as their self-reported time from menarchy to establishing regular cycles. And we plotted these trends over birth year categories, and that's where we found the declining trend as well as disparities across different self-identified race and ethnicities. Gotcha. I have a question for you. How, especially among older generations, how reliable is the

information about period regularity? Like, I remember how old I was when I got my period, but I can't really remember how old I was when my period got to be regular. That's not really something I was tracking, particularly before iPhones existed, you know? Yeah. I would say there's still like a gap in research and just studying menstrual health, especially menstrual health during adolescence in general. There have been some other studies documenting that the reliability of self-reported Asian monarchy is actually pretty high, but we are not sure whether like self-reported time from menarchy to regularity are also kind of as reliable as agent menarchies. So this is something that we need to look into the future.

Right, that makes sense. So based on the information that you've collected so far, do you expect this trend of early monarchy to continue into the future? Yeah, so this declining trend is actually not like super new because other cities have also documented in like earlier years that this trend is happening. And we're seeing also among like the generations born between 2000 to 2005 and this is continuing. So I think there's reason to believe that this trend will continue unless we work on the tangible solutions that might be contributing to this trend and disparities. How might starting their period earlier impact to kids long-term physical and mental health? Yeah, this is a good question. So a part of the reason that we're trying to document this trend is really trying to make parents and clinicians aware.

that we should be more prepared for children experiencing their first period at an earlier age and that so that people can initiate like proactive discussions around menstruation early on like from the educational standpoint this could really help foster the understanding and reduce the feelings of shame or embarrassment that is often tied to like their first period and just recognizing menstrual house as a vital sign. Great. Are there are there are there physical effects of starting periods earlier as well, though? Like, are there sort of long-term health effects? Yeah. Some of the long-term health effects that I mentioned earlier are, like,

just increased risk of metabolic conditions like diabetes, high cholesterol, and in the end, cardiovascular disease. Earlier, menarche and irregular cycles are also associated with higher risk of infertility or developing breast cancers later in life. Gotcha. So it's that it's both starting periods earlier and irregular cycles that both contribute to those things. But we haven't, we don't have necessarily like more granular data about which of those is contributing to what. Yeah. So other researchers have separately looked at how earlier minority plays a role in these disease conditions and then other groups of researchers have also separately looked at how longer time to regularity might also play a role. But it's still, at this point, it's still unclear whether they're, like, jointly impacting the outcomes or is, like, a sequential step.

Because there's definitely, like, a time element around these measures. So a study from last year found that black kids are more than twice as likely as white kids to start puberty early, which is, just so staggering. And now your study shows that black, Hispanic, and Asian kids all tend to start their periods earlier than white kids. Do we know why this is happening? Yeah, this is very concerning. And there are multiple possible explanations for this, but it's hard to really just pinpoint to one factor. In our analysis, we looked at how obesity might play a role. So we looked that, again, participants self-reported body mass index around the time of their first period. And we found that BMI at first period might be explaining about 46% of the trends

we're seeing in age at menarche, but we're still seeing remaining trends even after we adjusted for BMI in our analysis. So there could be some other possible players based on other researchers work, like things like air pollution, toxic chemicals from the environment, or limited access to healthy food, all of which are also disproportionately impacting people of color. Unfortunately, in our analysis, we are limited in our data to really further investigate these factors. So we definitely need more research on this area as the next step to work on the more modifiable or tangible solutions to these trends and disparities. You know, we know, we know. that a lot of socioeconomic factors are connected to a person's overall health, you know,

like access to health insurance or if you live in a polluted area, those things will have a big impact on how healthy a person is. Do we know how much of the results of this study are, you know, correlation versus causation? So for this study, we are really just trying to document the trends that we're seeing. We didn't really adjust for any, like, what you call potential confounding factors. So our goal for this initial study is really just to show the distribution

and show the disparities across different disadvantaged socioeconomic groups. And in the future, we definitely want to do like more granular estimates, of is there a factor that's causing this trend versus it versus it really just a correlation? This is just sort of a basic question, but how well researched is menstruation? You know, it's something that roughly 50% of the population does in their lives at some point, but how much do scientists really know about it?

I'm so glad you brought this up. And it's interesting because a few years ago, our study team just looked up the search term of menstruation in the PubMed database. And we kind of looked at the period between 2001 to 2018 in PubMed. And there were only around like 8,000 publications relevant to menstruation. And in comparison, there were more than 900,000 publications on cardiovascular disease, more than 100,000 on prostate cancer, and interestingly, more than 16,000 on erectile dysfunction. and we know that menstruation is impacting, as we just said, around half of the population.

So there's definitely a gap there in terms of research in the menstrual cycle in general. Lately, including the Apple Women's Health Study, there have been like this emerge of digital app-based studies taken from menstrual tracking apps, for example. So hopefully we're on our way to work towards addressing these gaps. That's great. Do you think that it's just a matter of sort of representation of who's doing research, or do you think that there's sort of more urgency for other reasons? And that's why we're now seeing more research on menstruation in recent years. Yeah, we haven't really died into the reasons behind this gap. But in general, I feel that in more recent years, there has been more awareness

amongst the public as well as among clinicians to recognize menstrual cycle as an important vital sign. So, yeah, I think we're making progress here. Were you able to find past research from, you know, decades ago that you could compare with your results? Yes. There are multiple publications either within the U.S. or in like other developed countries that are also showing similar trends. in terms of decreased aged menarche. I will say that most of these studies, which were taken from an earlier time period, when they studied disparities,

they mostly just focus on black versus white disparities based on their data availability. So one of the novel things we found in this data is that this is not, first of all, this is impacting all reasons. ethnic groups. And second, this is not just impacting the black individuals, but also Hispanics and Asian individuals as well. You know, this is having an impact on a lot of people, as your study has found. If someone is listening to this conversation and either they or their kids had an early period or an irregular period and they're worried about the potential health effects,

what did you recommend that they do? Yeah, that's a good question. And speaking as as someone who wish to become a parent too. I think this does raise some alarms. And as a society, I think we should focus on greater investments in the early counseling education around menstrual health, as well as individualized health care plans early on during the life course. Individually, healthy lifestyle in general would be helpful, like physical activity and healthier diet. In our team, we did a separate research that looked at the association between

irregular cycles and cardiometabolic conditions. And we found that physical activity and BMI might modify the risk of cardiovascular disease associated with irregular cycles. So there are definitely some ways to kind of mitigate the risk even if you already had your first period. Right. Okay. That's great to now. You know, there's obviously a lot of information in this study that will be so important to understand further. What are you most interested in studying in the future? Yeah, our team is really dedicated to documenting the factors around menstruation and also menstrual hygiene for an overall goal just to first reduce stigma around this topic. And as subsequent steps, we are utilizing the knowledge and methods that we have.

to identify the modifiable factors to reduce risk across the lifespan. Well, that's all the time we have for now. I'd like to thank my guest, Dr. Zifan Wong, postdoctoral research fellow at Harvard in Cambridge, Massachusetts. Thanks for joining us. Thank you. That's all the time that we have for now. A lot of folks help make the show happen this week, including Annie Nero.

Jason Rosenberg. Rasha Eredi. Shoshana Bucksbaum. And many more. Tomorrow, we'll talk about a new book that posits that the Earth itself is alive. But for now, I'm SciFRI producer Kathleen Davis. We'll catch you then.