Actigraphy

The word for this week is actigraphy. Actigraphy uses a device with a movement sensor in it. The sensor looks at body movements. It then puts this data into a computer. The computer can tell when an individual is asleep or when they are awake. Some devices that people use themselves do the same kind of recording.

Recently, a group in England used actigraphy to study sleep patterns. They used the information to detect health patterns. The study had 86,565 participants. They followed them for eight years. Over that eight-year period, 5,189 (6 percent) of the participants died.

They then looked at daytime napping patterns in that group of individuals. They made sure that other factors were the same as the 94 percent who survived. The deceased group was not more obese. The deceased group did not smoke more. The deceased group did not drink more. The deceased group did not have different nighttime sleeping patterns.

The American Academy of Sleep Medicine currently encourages healthy adults to limit naps to 20 – 30 minutes. Such “power” naps can improve daytime alertness. It can also improve performance.

Naps longer than 30 minutes are more likely to make a person feel groggy after waking up. For that reason, they are discouraged.

The group they studied with actigraphy did show evidence of daytime naps. The naps averaged 24 minutes each. Therefore, the amount of time spent napping was consistent with the recommendations.

However, naps were taken at different times of day. About 34 percent of naps were taken between 9 a.m. and 11 a.m. Another 24 percent were taken between 11 a.m. and 3 p.m. Then 19 percent of naps were taken between 3 p.m and 5 p.m. The final 22 percent of naps were taken between 5 p.m. and 7 p.m.

The data showed that napping between 11 a.m. and 3 p.m. was associated with an increased risk for mortality for middle-to-older aged adults.

They also found that some patterns of napping were associated with greater mortality risks. Longer naps were one of the high risk patterns. Large variability in the amount of time spent napping was another high risk pattern.

This evidence is different than what is currently recommended. There are no specific times for taking a power nap.

The authors point out that their information is preliminary. More studies need to be done. They also point out that if someone is engaged in an activity that has little movement, actigraphy computer algorithms can call it sleeping when it actually is not.

In the meantime, actigraphy suggests that daytime naps are not different than a lot of other activities. There are benefits. There are risks. Individuals with ADHD like me doesn’t know what a daytime nap looks like. I can do without a smartwatch to tell me I didn’t sleep all day.