For the video version of this post, click here.
While I usually review articles with thousands of patients in them, I've always had a soft-spot for small, well-conducted studies that answer an interesting question. Today, I'm talking about this study, appearing in the Journal of the American Medical Association.
This is a title you come across and are like "Huh, yes, I suppose that is something we should think about". Really, the clinical issue here is that the elderly are a vulnerable population when it comes to morbidity and mortality during a heat wave.
This graphic from the EPA demonstrates the number of deaths per year due to heat – we're talking about somewhere between 300 and 900 nationwide.
Heat-related hospitalizations are much higher. We're talking roughly 6000 individuals per year. Most of the deaths and hospitalizations occur in the elderly.
What could fans have to do with this? Well, they are a cheap and, presumably, effective intervention when it gets too hot outside. But they may carry some risk. Remember a fan's mechanism of action is to increase the evaporative cooling from sweat on your skin. You might postulate that this would be less effective in more humid environs and this is indeed what was found.
This is a small study. Researchers recruited 9 volunteers of a mean 68 years. Then, they put them in a hot room – at around 108 degrees Fahrenheit (42 Celsius). They kept them there for an hour and forty minutes, measuring heart rate and core temperature all the while. Each participant did this twice, once with a fan, once without it, on separate random days.
What they found was interesting. As humidity rose, the core temperature rose, stabilized, then sharply rose again, like this:
Similar results were found for heart rate. Of course, since relative humidity was increased in a standard fashion over time, we may not be seeing the effects of humidity at all, simply the effects of sitting in a very hot room for a while.
Did the fan help? Not really, in fact, it made things worse. When the fan was in the room, heart rates were generally higher by about 5 beats per minute, and core temperature by around 0.2 degrees Celsius.
But… how? The easy argument is fluid loss – with the fan you may become more volume depleted (participants weren't allowed to drink). But the average loss was 0.8 liters whether the fan was there or not. The authors don't provide a hypothesis as to this effect. Frankly, all I can think of is perhaps the noxious stimulus of something blowing hot air into your face or previously undiagnosed fan-phobia.
So – no fans for the elderly? Not so fast. Aside from the small sample size, this study was very controlled – perhaps too controlled. Number one offender: no access to water. With free access to liquids (as most of us thankfully have) the results could be very different.
While I am a fan of small, carefully done studies, I am left in the no fan group with this study's particular conclusions.