It's a Stressful Life

Everyone’s felt some kind of stress in their lives before. From an upcoming quiz in school to moving across the world to start over your life, there’s nothing that’s too big or too small to be called “stress.” Everyone’s stress is different, and everyone’s stress deserves to be looked at. 

When we age, a lot of things in our bodies begin to change. Things that came easily when you were young might be super hard 50 years later. Think about just walking to the grocery store. A 20-something college girl in a rush to get to class might burst out the front door and run down the street. That same woman at 70 years old would face a totally different situation. Before leaving the house, she might change the tennis balls on her walker. She might have to switch out her reading glasses. She has to be extra careful when crossing the street, so that cars don’t get frustrated when she takes more than 30 seconds to get to the other side. 

All that extra thinking and planning leads to a whole lot of stress. Not to mention, older people are way more likely to have experienced some kind of big stress, like losing a loved one or being fired from a job they really liked. But how do they experience stress? Let’s talk about it.

First of all, we need to understand something in our body called the hypothalamic-pituitary-adrenal axis (HPA, for short). This is basically just a grouping of glands in the body that push out hormones when you’re under stress. The most important hormone that the HPA is responsible for is called cortisol, which is called the “stress” hormone because it’s high in people who are stressed, but low otherwise. High cortisol is really bad, though, because it’s associated with a whole bunch of unfortunate health effects, like heart problems, high blood pressure, lower immune system functioning (meaning your body isn’t as strong when it comes to fighting off diseases), and higher risk of mortality. Basically, it’s not good.

Cortisol itself is kind of tricky to measure, because levels of it change throughout the day. In the morning, it’s usually low, but then as the day goes on, it can increase up to 5 times from what it was in the morning. This weird up and down fluctuation is called diurnal cortisol, diurnal meaning “during the day.” 

This study worked with 200 adults and found cortisol levels in the morning were significantly higher for older adults than younger ones, and that diurnal cortisol for older people fluctuated a lot less than younger adults. So while the cortisol chart (from morning to evening) might look like a wavy line for the 20 year old, it would just be a straight line for the 70 year old. At the end of the 10-day study, the researchers concluded the age-associated increases in cortisol and the endocrine system (the body system that houses the HPA and other hormonal pathways) reflect a lifetime of stress. 

But which kind of older people are more likely to have these kind of cortisol problems? An interesting question, and luckily, these researchers did the work for you! The effects of age-related cortisol changes seem to be stronger in men; for example, older males have higher cortisol when they wake up, and their diurnal cortisol (the change from sunrise to sundown) seems to flatter than that of older females. While the reasoning behind this isn’t totally concrete, the researchers think age affects men’s cortisol levels more because of how their bodies operate differently on a hormonal basis (we know men and women have different hormones, and cortisol is, well, a hormone).

Remember when I talked about the hypoth-whatever (we can just call it the HPA) and how bad things happen when it’s not working properly? Well, turns out there are two molecules in the body that are pretty important in controlling how the HPA works. For one, we have corticotropin-releasing hormone (CRH); for another, we have arginine vasopressin (AVP). CRH directly controls how the HPA works, so when CRH goes up, the HPA starts working, and cortisol goes up. AVP was discovered before CRH, so CRH kind of hogged the spotlight once it was discovered and people don’t really think about AVP anymore (but we will!). Unlike CRH, AVP does some good things too, as it is really important in maintaining good sleep, good body temperature, and even stable memory. 

Why are we talking about these two molecules? Well, a lot of long-time stressful situations (stressors that take a long-time, like a broken ankle or the heavy traffic everyday on the way to work) activate AVP more than CRH. Simply put, the kind of stress we call chronic (or long-term) comes from higher AVP, not CRH. That’s certainly helpful information if we want to create newer treatment for stress! Because now we have to consider what kind of stress we’re in, and how the HPA is working in that specific kind of stress.

All in all, it’s fair to say that the HPA is super important for stress, and it’s more active in older adults, which hypothetically leads to more problems. But it’s also important to remember that there are a lot of nuances that make saying something for certain pretty difficult. Before telling someone how to manage their stress, you need to know their age, their gender, their past experiences, and what kind of stress they’re in. 

— Allie Yuxin Lin