At Jawbone, we’re proud to build products that help people lead healthier lives. With our UP line of trackers, people can track their activity, sleep, and heart health, and reduce the factors that negatively impact their overall health day to day. Of course, another important part of understanding health is understanding sickness—how and when we fall sick and recover.
To uncover the key to sickness and recovery, we looked at anonymized data from Jawbone’s fitness tracker and UP App, in particular, user comments on their own activity that included words related to flu. We computed a sickness likelihood score as the change in the fraction of flu related comments over the normal baseline and studied how this score varied with seasons and demographic factors.
WHEN DO WE FALL SICK?
A fascinating aspect of flu is that it is seasonal; it always occurs in winter, and while this connection has been known for a very long time, the reason is not clear. Several explanations have been investigated, such as people spending more time indoors with windows shut, lack of Vitamin D weakening our immune system, and flu viruses thriving in cold and dry winter weather—but, there is no consensus. In the United States, the flu season typically starts in October and peaks between December and February. This year, flu activity has been low so far, possibly due to the mild temperatures in most parts of the country. In Australia, flu season lasts from May to October—the Australian winter.
WINTER IS FLU SEASON
WHO IS MORE LIKELY TO FALL SICK?
Our chances of catching the flu vary depending on the strength of our immune system and our lifestyle. We looked at how the sickness likelihood score varies with age and BMI among UP users. Within each age group, we see that people with higher BMI were more likely to fall sick, except in the 55-64 year group where underweight individuals were most likely to fall sick.
BMI AND AGE INCREASE LIKELIHOOD OF FALLING SICK
There is also a clear relationship between average daily steps, a proxy for general fitness, and sickness likelihood. As the daily step average increases, the sickness likelihood decreases. For men aged between 25 and 45 years with a normal BMI, those with a daily step average of over 14,000 were four times less likely to fall sick compared to those with a daily step average less than 4000.
MORE ACTIVE PEOPLE ARE LESS LIKELY TO FALL SICK
Note: this graph looks at males age 25-45 with a normal BMI to minimize the confounding effects of gender/age/BMI.
HOW DO WE RECOVER?
The common wisdom is that resting is important for recovery, and that is what we see in the data. Everyone steps less, goes to bed earlier and wakes up later when sick. There is a 5-12% decrease in daily steps and 5-7% increase in sleep time when people are sick. Interestingly, middle aged adults have a smaller drop in daily steps compared to those younger than 25 or older than 55, which could be attributed to the nature of their jobs or roles as caretakers in the family.
THE OLD AND YOUNG REST WHEN SICK