Level of physical activity tied to less pain, blood viscosity in SCD: Study
Patients seem to meet, exceed recommendations for general population
Most people with sickle cell disease (SCD) seem to meet or exceed current physical activity recommendations for the general population, a recent study in Senegal shows.
Notably, greater step counts and time spent in more intense activities were associated with lower pain frequency and intensity, as well as lower blood viscosity, which refers to higher blood thickness due to the clumping of red blood cells.
These benefits may reduce the risk of vaso-occlusive crises (VOCs) in patients, but more research will be needed to fully establish this association, researchers said.
“These findings suggest that regular [physical activity] may confer clinical benefits in individuals with sickle cell anaemia, although further studies are needed to establish robust evidence-based recommendations,” they wrote.
The study, “Physical activity, vaso-occlusive crises and pain in patients with sickle cell anaemia in Senegal,” was published in the British Journal of Haematology.
Participants tracked pain with diary
SCD is caused by the production of an abnormal version of hemoglobin, the protein responsible for carrying oxygen in red blood cells, which causes these cells to acquire a sickle-like shape. Sickled cells are more easily destroyed and prone to stick to each other, blocking blood flow and leading to disease symptoms.
When sickled red blood cells block blood flow to the point that tissues become deprived of oxygen, patients experience painful episodes known as VOCs. These episodes may be triggered by several factors, including acute exercise, but it’s also believed that physical activity can reduce inflammation and blood viscosity, which could be beneficial to patients.
As a result, recommendations on physical exercise for people with SCD remain unclear.
To learn more, a group of researchers in Senegal set out to determine whether physical activity correlates with the occurrence of VOCs and pain. They recruited 104 male patients and 20 healthy individuals between 2020 and 2023, who were asked to wear a wristband device for five weeks to track activity while keeping a pain diary to record the occurrence and intensity of any pain. All participants were asked not to change their lifestyle during the study.
Each participant had an average of 33 valid days — when the device was worn for at least 10 hours — that were eligible for analysis. The days when VOCs occurred, including two days before and after a crisis, were excluded from the analysis.
Exercise intensity was expressed as the metabolic equivalent of task (MET), which measures the energy cost of an activity relative to the energy expended at rest. Light-intensity exercises, such as slow walking or light household chores, correspond to a MET of 1.5 to 2.9, moderate exercise such as brisk walking and recreational swimming to a MET of 3 to 5.9, and vigorous exercise like running and fast cycling to a MET of 6 or higher.
Research could lead to physical activity recommendations
Overall, 98 individuals with SCD, with a mean age of 29 years, completed the study. On average, participants walked a median of 9,611 steps per day and spent almost five hours (293 minutes) on light-intensity exercises, about one hour (64 minutes) on moderate-intensity exercise, and 28 minutes on vigorous activities. There were no significant differences in physical activity parameters between healthy participants and those with SCD.
The World Health Organization (WHO) recommends 150 to 300 minutes of moderate-intensity exercise or 75 to 150 minutes of vigorous exercise weekly, or a combination of both in equivalent amounts. Eighteen patients did not meet the WHO recommendations for daily physical exercise — the others were within the recommended range (18 patients) or exceeded it (62 patients).
Overall, 13 participants with SCD experienced a VOC requiring a visit to the hospital, while six experienced a VOC but did not go to the hospital.
Research that improves our understanding of the relationship between [physical activity] and [SCD] symptomatology could facilitate the development of [physical activity] recommendations for these patients.
An initial analysis demonstrated there were no significant differences regarding the median number of daily steps and the daily time spent on light, moderate, or intense exercise between patients who experienced VOCs with those who didn’t. However, after adjusting for blood viscosity, there was a significant, 19% increase in the chances of experiencing a VOC per every extra 1,000 steps.
Outside of VOCs, the median daily step count and time spent doing light or high-intensity activities were associated with a reduced frequency of pain days and pain intensity, as well as lower blood viscosity.
“Research that improves our understanding of the relationship between [physical activity] and [SCD] symptomatology could facilitate the development of [physical activity] recommendations for these patients,” the researchers concluded.
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