When wearable activity monitors first came on the market, it seemed like they were on everyone’s wrists. It was not long before they surfaced as mobile phone apps, making it convenient for anyone to monitor their activity, health, and fitness. Now the category of fitness wearables is not just basic activity wristwear, it includes a variety of jewelry such as bracelets and smart watches that track the wearer’s step counts and calories expended. These devices also log behavioral, sleep, and other physiologic metrics and can be synced with a computer or smartphone app that summarizes the data collected. Sales of smart watches alone are predicted to reach 141 million units by the end of 2018, and according to Forbes.com, 240.1 million wearable devices of different types will be produced in 2021.1,2Part of the reason for their popularity is that the medical community finds wearables ideal for tracking a patient’s health, and their use in the medical field is widespread. 

Wearables are particularly useful in oncology, since performance scales that evaluate a patient’s functioning and self-care can be limited. Although valuable, these measures may require some self-reporting from the patient and objective reporting from the clinician; in either case, the patient’s status could be misinterpreted, and this could affect treatment. Patients may have recall bias, or a bias toward enrolling in a clinical trial or receiving a different therapy, and they may skew their self-report towards this. Further, the commonly used performance status assessments are static and only performed during clinic visits, whereas a patient’s condition and performance are always in a state of flux. 

Gillian Gresham, PhD, of the Samuel Oschin Comprehensive Cancer Institute at Cedars-Sinai Medical Center in Los Angeles, California, and Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, and colleagues undertook a study to determine the feasibility of using wearable activity monitors to assess performance status in patients with advanced cancer. The device used was the Fitbit Charge HR®, which tracks step and stair counts, heart rate, calories expended, and sleep patterns.3

The study enrolled 37 patients, 20 men and 17 women, with a median age of 62. Most patients had stage 4 gastrointestinal cancer; 2 had advanced stage 3 pancreatic cancer and 1 had stage 3B endocervical serous carcinoma. The participants in this study had lower levels of physical functioning and higher levels of fatigue and pain than the remaining cancer population. 

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Activity Data Correlates With Performance Status

Over a 2-week period, the fitness trackers showed that the patients walked approximately 3700 steps (1.7 miles) per day, climbed an average of 3 flights of stairs per day, and slept an average of 8 hours per night as measured with the wearable activity monitor. Patients’ average resting heart rate was 68 beats per minute. The more active the patients were, the better their disease course was. An average increase of 1000 steps per day correlated with a significantly lower risk for hospitalizations, reduced adverse events, and increased survival. Patients who walked fewer than 1000 steps per day survived an average of 2 months, while patients who walked between 1000 and 2000 steps per day survived an average of 5.5 months. Reduced odds of hospitalizations and toxicity occurrences were associated with a higher number of stairs climbed. Conversely, patients who reported higher levels of fatigue showed decreased step counts, shorter walks, and fewer stairs climbed. Although nightly sleep duration was not associated with the frequency of hospitalizations or the occurrence of adverse events, the researchers observed a statistically significant correlation of sleep with overall survival.3

The investigators described a prior study that evaluated whether a different brand of fitness tracker, Garmin, could predict the likelihood of hospitalization in 38 patients undergoing concurrent curative radiation and chemotherapy for head and neck, gastrointestinal, or lung cancer. That study found that patients who walked an average of 5103 steps per day with an increase of 1000 steps per day had a 38% reduced risk for hospitalization.4Gresham and colleagues noted that their findings and those of the Garmin study demonstrate the feasibility of objective activity monitoring in predicting clinical outcomes such as hospitalizations in patients with cancer. They call for larger clinical trials to explore the possibilities posed by the use of fitness wearables in cancer care.

Bette Weinstein Kaplanis a medical writer based in Tenafly, New Jersey. 


1. Smartwatch unit sales worldwide from 2014 to 2018 (in millions). Statista website. www.statista.com/statistics/538237/global-smartwatch-unit-sales. Accessed August 15, 2018.

2. Lamkin P. Wearable tech market to double by 2001. Forbes website. www.forbes.com/sites/paullamkin/2017/06/22/wearable-tech-market-to-double-by-2021/#76623f8fd8f3. Posted June 22, 2017. Accessed August 15, 2018.

3. Gresham G, Hendifar AE, Spiegal B, et al. Wearable activity monitors to assess performance status and predict clinical outcomes in advanced cancer patients[published online July 5, 2018]. NPJ Digital Med.doi: 10.1038/s41746-018-0032-6 

4. Ohri N, Kabarriti R, Bodner WR, et al. Continuous activity monitoring during concurrent chemoradiotherapyInt J Radiat Oncol Biol Phys.2017;97(5):1061-1065.