Own a Dog, Don't Drink Soda, Take Vitamin D? How To Interpret Medical Headlines
How To Read Headlines
In this brief post, I will share a few simple tips that will help you better interpret medical stories you hear or read about in the news. The problem is that reporters aren't aware of the difference between an association and causation.
You may have seen these stories in the headlines recently.
"Dog owners live longer".
"Drinking soft drinks is associated with premature death from cancer and heart disease".
"People with Vitamin D deficiency have more heart disease".
1. "Dog Owners Live Longer...Especially if You Have Heart Disease"
Many people have suspected that owning a pet helps you live longer. Combining 10 studies (known as a meta-analysis), nearly 4 million dog owners were followed for 10 years. Dog ownership was associated with a 24% lower risk of death! And, if the dog owner had heart disease, risk of death was 20% to 65% lower!
This seems logical. Owning a pet provides stress relief. Exercise prevents heart disease.
Bottom line: Own a dog (?).
2. "People who drink soda die earlier"
Researchers in Europe found that death from cancer and heart disease was 17% higher if you drink 2 or more glasses of soft drink vs. 1 glass/month! Sugar free drinks were just as bad as sugar soft drinks.
This sounds reasonable. There are a lot of chemicals in soft drinks.
Bottom Line: Don't drink Coke or Pepsi (?)
Caution: Observation, Association, Correlation vs. Causation.
The point of this discussion is not for you to go out and buy a dog, stop drinking soda or start taking vitamin D--in order to live longer, prevent cancer or prevent heart disease. In fact, none of the above is proven.
Rather, it is to emphasize that many headlines or stories you come across are not actually 'cause and effect' but merely 'associations'. There is a big difference.
Tip #1: Know the difference between an association, a correlation vs. causation. (For the purposes of this post, I am not going to discuss study design, which is even more important).
Tip #2: Just because two things are associated (or correlated) does not mean one causes the other.
If drinking soda is indeed associated with a 17% higher incidence of death from cancer and heart disease, this does not mean that drinking Coke or Pepsi causes death, cancer or heart disease.
If people who own dogs may live longer, owning a dog is not proven to be the reason for longevity.
If low Vitamin D levels are associated with early cardiovascular disease, this does not mean that Vitamin D deficiency causes heart or blood vessel disease. It also does not mean you should stock up on vitamin D.
In each of the above examples, further studies would be required to prove cause and effect and to determine optimal monitoring and treatment.
Tip #3: When you read medical headlines, be sure to look for the word(s) 'association' or 'associated with'. If so, then you will immediately understand that there is no 'cause and effect'.
You know understand how to more accurately interpret medical headlines!
Note: Understanding your heart condition is not difficult. Patients become frustrated and confused when doctors don’t explain things clearly. If you don’t understand what your doctor is talking about, then you won’t be able to ask meaningful questions. I hope that my posts provide you with a framework that you can build upon to become an active participant in your healthcare.
Gregg M. Yamada MD FACC
Disclaimer: I hope you find my medical blogs to be educational, pertinent, interesting, and thought provoking. The information provided is educational and should not be taken as medical advice. I am a doctor, but I am not your doctor. Please schedule an appointment with your doctor to discuss these issues and to determine what is right for you.
© 2019. Gregg M. Yamada, MD FACC. All rights reserved