It's important to pay attention the the end of the article, which states this study "cannot be applied to other types of heat therapy such as infrared heat exposure".  This is also the case with "infrared saunas", which are not actually saunas in the first place.

Infrared enclosures will never provide the same environment as a true, traditional sauna, and can not claim any of the same health benefits (or studies).  In fact, some infrared enclosures have been recalled due to posing a fire hazard with faulty wiring, and the possibility of toxic fumes from interior finishes that should have never been used.

Traditional sauna bathing has many time tested health benefits, and studies are continually coming out proposing even more.  The same is not true for phony "infrared saunas".  It's easy to tell the difference between a traditional sauna and infrared enclosure.  A traditional sauna will have a sauna heater with hot rocks on top, onto which you can sprinkle water.  An infrared enclosure does not use any rocks, and can not employ any type of addition of water.  They typically use an electric heater built into the wall.

Stick to a traditional sauna, and enjoy the mental and physical boosts from your sauna bath.