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Physical fitness linked to neurocognitive outcomes of leukemia survivors
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Reduced exercise capacity may be linked to neurocognitive deficits among survivors of acute lymphoblastic leukemia, according to results of a cross-sectional study published in Cancer.
“We conducted our study on survivors of the most common childhood cancer, so we cannot extrapolate our results to survivors of other childhood cancers,” Kirsten K. Ness, PT, PhD, FAPTA, associate member of the department of epidemiology and cancer control at St. Jude Children’s Research Hospital, and Nicholas S. Phillips, MD, PhD, post-doctorate research associate at St. Jude Children’s Research Hospital, said in a statement to HemOnc Today. “However, a wealth of literature shows that exercise is beneficial in healthy children, older adults, breast cancer survivors and dementia sufferers. We would not be surprised to find that survivors of other types of childhood cancer would also benefit from exercise.”
Ness, Phillips and colleagues analyzed results of cardiopulmonary exercise testing and a 2-hour standardized neuropsychological assessment as well answers to a self-report questionnaire administered to 341 adult survivors of ALL (median age, 28.5 years; range, 18.4-44.6; 51% men; 86.5% white) and 288 adults who did not have cancer (median age, 32.2 years; range, 18.3-44.8; 52% women; 89% white).
Study participants completed cardiopulmonary exercise testing until they reached 85% of their predicted heart rate — submaximal due to the increased risk for cardiac events among ALL survivors — at which point researchers calculated their exercise capacity, measured as max relative peak volume of oxygen (rpkVO2).
After adjusting for age and sex, survivors of ALL had lower mean rpkVO2 measurements than controls (23.45 ± 7.37 mL/kg/min vs. 33.03 ± 7.39 mL/kg/min; P < .001). Researchers also observed a significant difference in the median time to reach 85% predicted heart rate between survivors (12.3 minutes; range, 3.2-18.4) and controls (10.7 minutes; range, 4-17.2; P < .001).
Survivors also scored lower on tests of focused attention (z score, –0.23 vs. 0.51; P < .001), commissions (z score, –0.15 vs. 0.06; P = .01) and detectability (z score, –0.13 vs. 0.11; P = .002), as well as on all tests for executive function, processing speed, memory and academics. Survivors also showed poorer emotional control (0.18 vs. –0.08; P = .007), self-initiation (0.15 vs. –0.07; P = .01) and working memory (0.56 vs. 0.29; P < .001).
Researchers then conducted multivariable modeling to explore the association between these neurocognitive and patient-reported outcomes and rpkVO2 — which they converted to metabolic equivalents (METs) for clinical relevance — in analyses adjusted for sex, age at diagnosis, cranial radiation, anthracycline, methotrexate exposure and tobacco smoking status. They compared median METs between survivors with or without neurocognitive impairment.
Results showed a one-MET increase in exercise tolerance among survivors appeared associated with better performances in verbal ability (P = .01), focused attention (P = .04), verbal fluency (P < .001), working memory (P = .03), dominant motor speed (P = .001), nondominant motor speed (P = .002), visual-motor speed (P = .004), memory span (P = .004), reading academics (P = .03) and math academics (P = .001).
Researchers noted that, because their study was cross-sectional, they could not determine the direction of the association between fitness and neurocognitive outcomes.
Follow-up should be conducted to determine whether interventions that help survivors get into better physical shape impact neurocognitive function, researchers noted.
“The results of our study would suggest that a small increase in exercise tolerance can have a big benefit,” Ness and Phillips said. “If you are already active and can tolerate walking briskly for 30 minutes or more, then increasing your activity by, say, playing basketball, riding your bicycle or rowing, can give you even more benefit. These low-cost, home-based activities could be beneficial if done consistently enough so that your exercise tolerance improves.” – by John DeRosier
For more information:
Kirsten K. Ness, PT, PhD, FAPTA, can be reached at St. Jude Children’s Research Hospital, MS 735, Room S6013, 262 Danny Thomas Place, Memphis, TN 38105-3678; email: kiri.ness@stjude.org.
Nicholas Phillips, MD, PhD, can be reached at St. Jude Children’s Research Hospital, MS 735, 262 Danny Thomas Place, Memphis, TN 38105-3678; email: Nicholas.phillips@st.jude.org.
Disclosures: Ness and Phillips report no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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