Smartwatches Show Promise for Depression Prediction, Gaps in Blood Pressure Monitoring

Wearable trackers can detect the subtle signs of a depression relapse weeks or even months before an actual episode, according to new research published Feb. 11 in JAMA Psychiatry. The study followed 93 Canadian adults for up to two years, all with a diagnosis of major depressive disorder who had previously recovered from a depression episode.

By analyzing more than 32,000 days of data from research-grade devices similar to a Fitbit or Apple Watch, scientists found that a person's daily rhythms tell a story. Specifically, people with irregular sleep schedules had nearly double the risk of falling back into a depressive episode. The most telling sign wasn't just how long someone slept, but how different their day was from their night. When the data showed less of a difference between daytime movement and nighttime rest, a relapse was often right around the corner.

Major depressive disorder is a recurring challenge for many, with about 60% of patients experiencing a relapse within five years of recovery. Roughly 16% of U.S. adults are faced with it in a given year. Traditionally, doctors have had to wait for patients to report symptoms — like low mood or loss of interest — which often appear only after the depression relapse is already in full swing.

By collecting data passively, digital health wearables allow for continuous monitoring between doctor's appointments. This "always-on" approach could revolutionize how mental health is managed, moving from reactive treatments to proactive prevention. "Imagine a future where a smartwatch can warn people with depression: 'A new episode of depression is very likely coming within the next four weeks. How about seeing your health-care provider?'" said a professor of psychiatry at McMaster University in Hamilton, Ontario, Canada.

Separate research on lifestyle factors found that replacing 60 minutes of TV with something more active cut depression risk by 11% — and nearly 19% in middle-aged adults. Dutch researchers who followed more than 65,000 adults for four years found that for 90- and 120-minute reallocations, this decrease in likelihood goes up to 25.91%. The findings were published in the journal European Psychiatry.

While nearly every alternative to TV lowered depression risk, no meaningful benefit beyond a tidier home was found in swapping 30 minutes of TV for household chores. But spending that half-hour in sports reaped an 18% benefit overall, and replacing that same amount of time with physical activity at work or school reduced risk by 10%. Even commuting and sleep paid off, by 8% and 9%, respectively. Across all time frames studied, sports delivered the greatest reduction in the probability of developing major depression.

Significantly, shifting time from TV to more active pursuits did not have a significant benefit on depression risk in younger adults. Researchers suspect that's probably because they tend to be more active in the first place as a group. They may already exceed the activity level that provides protection against depression. In addition, simply reallocating TV time to other activities did not significantly alter depression rates in older adults. Doing sports activity was the only alternative to TV that made a difference for them. Replacing 30 minutes of TV with sports reduced the probability of depression from 1.01% to 0.71%. With 60 minutes, the risk dropped to 0.63%, and with 90 minutes, to 0.56%.

Meanwhile, research on wearable cardiovascular monitoring revealed critical gaps in Apple Watch high blood pressure alerts that might leave users with a false sense of security. There are critical gaps in Apple Watch high blood pressure alerts that might leave users with a false sense of security, researchers reported Feb. 9 in the Journal of the American Medical Association. In essence, the absence of an alert should be less reassuring for seniors than for younger people.

The U.S. Food and Drug Administration cleared the Apple Watch's high blood pressure notification feature in September. The watch doesn't use a traditional cuff to gauge blood pressure, but instead uses its optical sensors to track blood flow patterns. Apple has said the watch is not intended to diagnose high blood pressure, but is designed to prompt users to see a doctor if high blood pressure is suggested.

A validation study run by Apple found that about 59% of people with undiagnosed high blood pressure would not receive an alert, while about 8% of those without high blood pressure would receive a false alert. With more than 200 million Apple Watch users worldwide, the Hypertension Notification Feature offers new opportunities to identify adults with undiagnosed hypertension, but with potential for hypertension misclassification as well.

Results showed that among adults under 30, receiving an Apple Watch alert increases the likelihood that they have high blood pressure from 14% to 47%. On the other hand, not receiving an alert lowers their likelihood to 10%. For adults 60 and older, an alert raises the probability from 45% to 81%, which makes sense given middle-aged folks, and seniors are more likely to have high blood pressure. However, not getting an alert minimally lowers their odds of having high blood pressure, reducing it from 45% to a still-elevated 34%.

The same holds for Black adults, who have a higher risk of heart disease. Receiving an alert increases the probability of high blood pressure from 36% to 75%, but not receiving an alert lowers the probability only to 26%. By comparison, an alert among Hispanic adults increases the probability from 24% to 63%, and the absence of an alert reduces the probability to 17%.

These results show that smartwatches can supplement standard blood pressure screening, but should not replace it.