As a long term sleep enthusiast, I built the “Heart Chart for Office Workers” app to analyze data collected by my Apple Watch. The data collection experiment is still running and I have over a year of data to share with you

Normally, people have very hard time remembering what they did 4–5 days ago. What did you eat? Did you stay up later to watch some TV show? It all blends together, but those decisions affect your entire working week. I wanted to know how, so I used Apple Watch as activity tracker to answer the following questions:

Is my life consistent? Do I spend too much time on entertainment? Do I chisel into the nighttime by electronic device use? How stressful is my life? Are my vacations relaxing or chaotic?

How I collected the data.

Apple Watch automatically collects heart rate and activity data when worn. So I simply wore the watch all day long, charging it while taking showers. After turning off the “Raise To wake” and “Wake for Crown” features, I’m seeing up to 3 days of battery life. The only problem I experienced is that Apple Watch does not seem to collect data when the watch is locked, resulting in quite a lot of blank areas on my charts.

What is this chart and how to read it?

The charts below are an attempt to summarize hundreds of thousands of data points collected by Apple watch. Each individual row is 48 hours — two days stitched back to back. The 7 rows between horizontal white lines are 1 week (you can zoom in on the tiny white labels to read the week start date). Because of the way the data is plotted, you can clearly see a vertical green segment — those are my nights. The vertical yellow segment in the middle is my day

What do colors represent?

Gray — no data available (watch charging, forgotten or locked and bugged)

Light green — lowest heart rate, less than 65 BPM

Dark Green — low heart rate (physically sedentary, inactive, relaxed in bed)

Yellow — medium — typical sedentary heart rate, sitting upright, very light activity

Orange — high — physical activity like housework or sedentary stress

Red — maximum, walking, exercise or heavy physical activity. (90+ BPM)

The biggest advantage of plotting data like this is the ability to visually compare your results against other people.

Let’s begin the analysis!

Our bodies should rest at night, meaning seeing lower heart rate at night is expected and is also indicative of more restful sleep.

Living in the stress zone

The chart below captures how my heart responded to two months of different work environments. Following a short business trip. The pace and pressure of work picked up, as I got to fix issues in a large software project.

Compare the color of my sleep — what used to be primarily light green turned dark green with yellow, indicating a consistent increase in heart rate over the course of the night. The days, which were “normal” now had my heart consistently beat in the 90 BPM range for hours at a time.

Having a chart like this in real time helped me catch the situation as it was unfolding, notify my managers that I’m having increased stress levels and head out for a vacation before the situation turned critical.