Category Archives: Heat

better another day, correlation, Heat, icecream, Multiple Sclerosis

Hot Summer Days and Icecream

When I was in Psychology 101, we learned about the difference between causation and correlation. I think of this now because of the story used to illustrate the difference. It seems there is a strong correlation in NY city between ice cream sales and murders. As ice cream sales go up, the rate of murders per day also go up. Nobody seems to believe buying ice cream causes murders despite the old saying of “we all scream for ice cream.” Simply put, more people are out and about interacting when it’s not well below freezing. For what it is worth the temperature is well correlated with both numbers as well.

This story comes to mind because we have hit a hot spell and with it have come all the tempers and misbehaviors of overheating and dehydration. It got to the point where A was not going to be allowed to go on a pirate ship camp outing unless a parent attended too. I guess maybe some would have been angrier than I was, but in truth, it was fun to go interact with my kids in a school setting and see how the school personas behave. It is very different from home. Watching them excitedly introduce me to friends and what they have been doing in camp was well worth taking a day off. Still, I tried to pretend I was annoyed I had to be there to avoid reinforcing the bad behavior.

It turned out to be a very good thing I went, or I would have felt far more left out as I stayed home while J took the kids to the pool both days this weekend. It is not a lack of desire to be with my family as I very much wanted to watch them learn to swim and play with their friends. It is just heat and I do not get along. I tell myself I would go 3 out of 4 times. I tell myself “it is just this time I need to sit out.“

At heart, I fear I am a liar.

I think I will go get some ice cream and wish I did as well in the sun as the flowers in our front yard. I am turning ever more into the anti-superman. The yellow sun saps me rather than strengthens me. Maybe I just need some kryptonite to get me going. Then maybe I could recapture the strength to be outside helping as my son decides to learn how to ride a bike without training wheels and does so in a single day.

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Heat, MS, seasonal adjustment, seasons

Heat’s Impact- Can We Have a Little More Cold Weather Please?

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I was thinking about our incredibly warm winter during lunch today.  When I got back to my computer, I saw an interesting study.  The study by the Kessler foundation was released this week showing warmer temperatures are associated with worse cognitive statuses of people with MS. http://kesslerfoundation.org/media/displaynews.php?id=220
While this information comes as no surprise to me, somebody who barely functions when warm, it does pose some interesting methodological problems for further studies or clinical trials.  The variation of individual reactions to temperatures may make larger studies even more important despite the added costs.  If a study has only a minimum number of patients thought to allow the determination of a technically statistically significant finding from a math point of view, it may in fact be reporting the significance of a small number of people’s  reaction to a difference in temperature or season.
If one could have enough people in a study, then one could adjust the results by the average impact the temperatures would have caused.  In other surveys, this same approach is done and referred to as applying a “seasonal adjustment.”  If one thinks of hiring, the term takes on a more obvious role than in a medical study.  Stores hire sales people for the Christmas season.  So when they say, “the hiring for Nov is up 5% from October Seasonally adjusted” it doesn’t just mean the economy added 5% more jobs.  If the economy normally adds 10% on average from October to November, the 5% is cumulative with the 10% normal boost.  Depending on methodology the 5% increase may be before or after the adjustment.

This article makes a case for such an adjustment when looking at MS stats and clinical trials.  If one takes this information at face value, I would be trying to run my clinical trials for new drugs/procedures during the coldest times of the year in the coldest places as my end points so I could hide/offset some negatives in the positive impact of the change in temperature.  Of note, the studies used for this were small with 40 MS patients for one time period and 45 MS patients from a different pool at the second point in time.  There are some with MS who can’t take the cold but are fine in the heat, the opposite of my reaction.  Had there been a couple of them in the trial, the results could have come back opposite what is being published here.

I am not saying I disbelieve the results or think they don’t point to some thing of importance when trying to determine the validity of different tests and trials.  In fact, based on personal experience, I would believe the results most likely valid enough to warrant further testing to determine a seasonal adjustment.  In a large study, this type of seasonal adjustment may lead to more correct identification of significant trends rather than those trends caused solely by weather.

One last note on the structure of the study’s results: they are reporting a significant correlation.  There is a saying “correlation does not equal causation.”  For example, in a NY City study, ice cream sales increased as outdoor violent crime increased.  Does ice cream cause us to murder each other?  We may all scream for ice cream, but murder?  Isn’t it just as plausible to think people buy and eat ice cream during the spring, summer, and fall when going outside is comfortable.  Then they buy less ice cream in the winter when they stay inside and thus aren’t outside to either perpetrate violent crimes or be victims of them? (note the seasonal adjustment needed for even this study)Smile 

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