In a recent report, Apple outlined the “rigorous scientific validation processes” used to develop the health and fitness features baked into its products.

Wearables like Apple Watch monitor our bodies around the clock, providing health insights in real time. That’s a new and unprecedented development in medical technology. The benefits are already clear, as the report illustrates, with anecdotes about how Apple Watch has saved lives.

But anecdotal evidence is not the same as scientific research. By cherry-picking the best outcomes, anecdotes risk overlooking the bigger picture. Scientists must look at all the outcomes, not just the good ones. With that in mind, I took a closer look at the scientific studies cited in Apple’s report, to find out what they tell us about the impact Apple Watch is having on our health.