With a heat wave rolling across the country, it comes as little surprise that "portable air conditioners" is currently trending on Google. After a relatively cool spring in many parts of the country, Memorial Day weekend saw temperatures into the 90s in many parts of the southern and eastern United States. No heat-related deaths have been reported yet, but cities are already reviewing their plans to deal with the heat. One of the more controversial aspects of heat waves, sadly, is that certain parts of cities see higher mortality rates than others. Why is this the case?

In 2006, sociologists at Ohio State and Western Washington University teamed up with a professor and a doctoral student in health studies at the University of Chicago to analyze the infamous 1995 Chicago heat wave, which resulted in over 500 heat-related deaths over five days. Like other studies, this one found that lower-income neighborhoods saw higher mortality rates, but with an additional explanation. The authors noted that neighborhoods with "commercial decline" (broadly speaking, a less vibrant business community) were even more closely correlated with high mortality rates. (Other factors often linked to low-income neighborhoods--higher crime rates, for example--did not correlate as strongly with the mortality rates.) Because many victims of the heat were elderly, the writers suggested that, in neighborhoods with more businesses, elderly suffering from the heat were more likely to leave their apartment and go into a nearby business and use their central air to cool off. Without such stores, they were more likely to stay in their apartments and suffer from the heat.