More children = lower blood pressure

By Razib Khan | January 14, 2010 6:10 pm

Raising Kids May Lower Blood Pressure:

A new Brigham Young University study found that parenthood is associated with lower blood pressure, particularly so among women.

The study involved 198 adults who wore portable blood pressure monitors, mostly concealed by their clothes, for 24 hours.
The monitors took measurements at random intervals throughout the day — even while participants slept. This method provides a better sense of a person’s true day-to-day blood pressure. Readings taken in a lab can be inflated by people who get the jitters in clinical settings. It’s a real phenomenon known as the “white coat” effect, and it can mess up the results of studies done without the portable monitors.
A statistical analysis allowed the researchers to account for other factors known to influence blood pressure — things like age, body mass, gender, exercise, employment and smoking — and zero in on the effect of parenthood. For parents overall, the 24-hour blood pressure readings averaged 116 / 71.
All other things being equal, parents scored 4.5 points lower than non-parents in systolic blood pressure (the top number) and 3 points lower than non-parents in diastolic blood pressure. Holt-Lunstad says the size of the difference is statistically significant, but she warns against hastily making major life changes based on this finding alone.

This finding is interesting because it seems to go against our expectations. I assume that there’s no real direct physiological process at work here; e.g., hormone changes due to pregnancy or lactation reducing blood pressure. Rather, it is likely that the choices one makes in life are strongly shaped by having children, and those choices somehow modify health outcomes in ways we don’t have a good grasp of yet. The researchers controlled for the variables which they knew about, but there are surely many hidden ones which are the real causes of the effect seen here. Pretty typical correlational study, novel for the against-expectations sign of the value.
Also, I do think it’s a little amusing that the work comes out of Brigham Young University. Presumably the authors know a lot about the pro-natalist lifestyle from personal experience. And Mormon “clean living” has resulted in lower morbidity and higher life expectancy from what I have heard.

  • becca

    I should think it obvious. Raising kids involves occasional moments of total panic, which gets your heart racing as well as a 5k. Since running 5ks should lower your overall bp, it makes sense that parenthood would as well.

  • Donna B.

    Along with the moments of total panic becca mentions, there are also the moments of complete hilarity where you can’t stop laughing. Isn’t laughter supposed to release some good chemicals in the brain and body?
    Also, the first unsolicited hug and kiss from a toddler is pretty good therapy.
    oh dear… it’s obvious this grandma is overdue for a dose of toddler.

  • agnostic

    My first thought was that it’s because of all the iron they’re getting rid off with each pregnancy. Your body has no way to dispose of iron other than bleeding, and pathogens use it as their nutrition source. (There’s a selfish reason to donate blood — get sick less often.)
    But after googling, the iron – blood pressure connection isn’t so clear.

  • Ford

    I couldn’t find the actual article on-line. Based on evolutionary trade-offs between reproduction and longevity (see link), I would have expected the blood pressure that maximizes fertility might not be optimal for long-term health. Once a woman has kids, however, living long enough to care for them may increase Darwinian fitness more than having more of them. So it would be interesting to compare pre- and post-reproductive blood-pressure with family size.

  • Trey

    Funny, I was just about to blog about this after hearing it on NPR.
    Having been to BYU, having life-long hypertension and having kids, I found it interesting to say the least.
    We are adopting our second and I had a bit of a row with our first this morning, so I wasn’t so inclined to believe it. Till she came and gave me a big hug and my heart melted.
    @Becca, Hmm, maybe those moments of total panic and frustration ARE like exercise. That’s the explanation I’m going with anyway 😀
    I have to admit, being gay and a gay parent, and having some crappy stuff come out of BYU directed to gays and gay parents, I was skeptical of this research a priori. Shouldn’t be, I know great research comes out of BYU, and from what I see of this study, it looks pretty good. Just sad BYU colors itself biased that way, sad for them.

  • Tod

    Maybe this is more to do with health that a person already had being reflected in their subsequent fertility; prenatal testosteronization (digit ratio) is related to risk of heart attack and number of children fathered.
    Moreover having fathered 4 or more children by age 30 increases a man’s chances of living to age 100 by 100-200%. Here

  • Tom Bri

    Exercise effect. If you have kids you know what I mean. Lots of running. When was the last time you played tag, hide and seek etc as an adult?

  • Clark

    I wonder if this varies according to the age of the children. Recall that sleep deprivation tends to increase blood pressure. Yet in larger families there is more likelihood for some help by older kids. I’m not saying this is the reason but I’d like to see the figures based upon oldest/youngest ages.

  • Caryn

    Pregnancy is known to remodel (at least some of) the vasculature permanently. It can also have lasting effects on blood pressure.

  • Roger

    Good health is correlated with fertility. That is the most obvious effect. Isn’t that enough to explain the result?

  • Tom Bri

    Took my kids and their friends sledding today. Spent the afternoon sliding down and climbing up a big hill. Lots of good fun and exercise. Kids equal exercise.

  • Monado

    Isn’t there a large benefit of having a strokable pet, so much so that it improves chances of survival after a heart attack by about 40%? Maybe it’s the same cuddling children. Or maybe having children increases the chance of having pets, too. Or maybe children really do bring a deep satisfactions.

  • MPL

    Parenthood / non-Parenthood has got to be the mother of all selection biases.
    Seeing as a randomized intervention study would have a few ethical problems, it would probably make more sense to follow this up with a longitudinal study—are parents simply healthier people to start with, or does their health relatively improve when they become parents?
    Also, a longitudinal study might help deal with the fact that employment, exercise, smoking, etc. are not necessarily independent of parenthood—e.g. if becoming a parent encourages some people to give up smoking, the study would actually underestimate the health benefits of parenting.

  • Tod

    Smoking and drinking are not independent of testosteronization or sex drive going by Sensation seeking, puberty, and nicotine, alcohol, and marijuana use in adolescence.
    People may be more likely to stop smoking when they become parents but smokers are probably a lot more likely to become parents in the first place.


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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


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