This week’s freezing temperatures and winter storms in Texas led to far fewer power outages than a similar freeze last year. But worryingly, a handful of Texas counties with high rates of power outages also have high numbers of people who need power for medical devices, according to a new analysis by the data group CrisisReady.

Losing electricity in bitter cold is always dangerous, but it’s particularly scary for people who rely on it to keep medical devices like ventilators running. The new analysis pulled federal data on Medicare beneficiaries to identify counties with high numbers of people using electricity-dependent medical equipment. It found that six such counties had more than 1 percent of the population out of power at one point during the storm. Lamar County — home to under 50,000 people — had a high percentage of people without power and also has nearly 900 people dependent on medical devices that need electricity.

The tens of thousands of people who lost power in Texas this week pales in comparison to last year’s cold snap-induced outages, which affected millions and led to the deaths of hundreds of people. Many people affected in last year’s storms also relied on medical devices and had to scramble to find ways to keep things like ventilators running.

But even smaller outages can be devastating if they hit vulnerable groups. Research shows that hospital visits for things like respiratory problems go up after power outages, and some might be from people left unable to use things like oxygen tanks. And the problem is getting worse: 2020 was the worst year on record for power outages in the United States, and the changing climate means weather-related incidents that stress grids will be a growing problem. Experts hope that we can build more backstops into our power systems so those incidents don’t keep cutting off electricity.

“Hopefully we become more resilient as the climate continues changing, rather than this all getting worse,” Joan Casey, an environmental epidemiologist at Columbia University Mailman School of Public Health, told The Verge last year.