To the Editors:
We read with great interest the results of the study by Raso et al,1 evaluating the associations between handgrip strength and physical function measures in 40 ambulatory male patients in Brazil, 20 of whom were at CDC stage C. In this exploratory study, the authors found substantial significant negative correlations between handgrip strength and 3.33-m walking, chair-rise, and shoe tying time (r = −0.58,−0.63, and −0.46, respectively). They suggested that handgrip strength could be a valuable measure of functional performance in HIV-infected patients and recommended that this should be confirmed in future research.
Here, we report the results of handgrip strength and functional locomotor assessments in 208 ambulatory HIV-infected patients in Southwest France, enrolled in a substudy of the ANRS CO3 Aquitaine Cohort. The cross-sectional data presented were collected during the follow-up phase of a study on locomotor functions,2 which included both functional tests and assessments of grip strength at the second study visit. Patients were eligible if they were HIV-1–infected adults participating in the ANRS CO3 Aquitaine Cohort, had neither acute opportunistic infections nor cancer under treatment, and were able to stand and walk. The study was approved by the Ethics Committee of Bordeaux (CPP du Sud-Ouest et Outre Mer III), and a specific informed consent was obtained.
Study participants underwent functional tests of lower limb performance (5 times sit-to-stand test, 5STS), global functional capacity (6-minute walk distance, 6MWD), 10-m walking speed, and balance (timed up and go test, TUG; and 1-leg standing with eyes closed), according to previously described procedures.2 Grip strength of the dominant hand was measured by a Jamar dynamometer (Sammons Preston Rolyan, Bolingbrook, IL), and mean grip strength across 3 trials was recorded.3 All locomotor assessments were performed by trained study staff according to standardized protocols. HIV-related and sociodemographic characteristics of the study participants were extracted from the central database of the ANRS CO3 Aquitaine Cohort.
We used Spearman correlation coefficients to assess correlations between handgrip strength and functional test results. Multiplicity adjustment of P values in the correlation analyses was performed by using an adaptive Hochberg procedure.4 Wilcoxon rank-sum tests were used for comparisons between 2 independent groups. All statistical analyses were performed with SAS software (version 9.2; SAS Institute, Cary, NC).
Among the 208 patients available for this analysis, 82% were male, with a median age of 50 years [interquartile range (IQR), 45–57] and median body mass index of 22.5 kg/m2 (IQR, 20.8–24.8). Twelve percent had acquired their HIV infection through intravenous drug use, and 55% were men having sex with men. CD4 cell nadir (available for 171 participants) was 245 per cubic millimeter in median (IQR, 151–374), and 26% were at CDC disease stage C. The majority of participants had markers of a well-controlled HIV infection at the time of the locomotor evaluation, with 97% on antiretroviral treatment, 93% having HIV-1 RNA levels <500 copies per milliliter and median CD4 cell count of 572 per cubic millimeter (IQR 411–779).
The participants' locomotor test results were distributed as follows: median (IQR); grip strength 41 (35–47) kg; 5STS time 10.3 (8.8–12.1) seconds; 6MWD 525 (480–585) m; 10-m walking speed 2.0 (1.8–2.2) m/s; TUG 5.1 (4.7–5.7) seconds; and 1-leg standing with eyes closed 17.7 (7.2–30.0) seconds.
In the overall study sample, correlations between handgrip strength and functional tests were weak (Table 1). Because our study population differs from the one in the study by Raso et al in terms of gender and of indicators of immunodeficiency, we performed additional exploratory analyses stratified by gender and CD4 cell nadir. We observed a tendency for stronger correlations between grip strength and functional tests in the subgroups of women and of patients with CD4 cell nadir <200 per cubic millimeter, respectively (Table 1). However, even in these subsets, the correlations remained weak, with only 3 coefficients reaching moderate correlation levels of >│0.50│ in women.
Furthermore, we assessed the association between locomotor tests and self-reported locomotor limitations in the overall study sample. When asked before performing the locomotor tests whether they considered having difficulties with regard to balance or walking ability, 32% of the participants indicated balance difficulties and 15% indicated walking difficulties. Performance in all functional tests, but not grip strength, was significantly worse in participants with self-reported balance or walking difficulties compared with those without any self-reported difficulties (5STS: median 11.7 vs. 10.0 seconds, P < 10−3; 6MWD 510 vs. 530 m, P = 0.04; 10-m walking speed 1.8 vs. 2.0 m/s, P < 10−3; TUG 5.4 vs. 5.0 seconds, P = 0.01; 1-leg standing with eyes closed 8 vs. 25 seconds, P < 10−3; and grip strength 41 vs. 41 kg, P = 0.26).
In summary, we found only weak correlations between grip strength and various functional locomotor tests in this large unselected sample of HIV-infected outpatients, fairly representative of the current situation of treatment and viro-immunological control in HIV-infected patients in care in France.5 Moreover, in contrast to the functional locomotor tests, grip strength was not associated with self-reported balance or walking difficulties.
Our study included a spectrum of validated functional locomotor tests, which were selected on the basis of their previous use in large-scale studies and their predictive values for falls, health status, and disability in the elderly general population.6–9 As in published studies on normative data for grip strength,10,11 and in contrast to Raso et al, who reported the maximum measured grip strength value, we analyzed the mean value across several trials. Both methods have shown excellent reliability, with a trend for highest reliability when using the mean value.12
The characteristics of our study population differed from those reported in the study by Raso et al,1 in which all participants were male and 50% had CDC stage C. However, it seems implausible that the difference in gender distribution explains the weak correlations observed in our study. Indeed, our subgroup analyses suggest that the correlations in our study population may be consistently weaker in men than in women across all functional tests.
Other participant characteristics, such as the extent of immunodeficiency during the course of the HIV infection, reflected by the CDC stage and the CD4 cell nadir, may thus contribute to the differences with the Brazilian findings. The majority of our study population had a well-controlled HIV infection, with a median CD4 cell nadir >200 per cubic millimeter, only 26% of the participants at CDC stage C and 93% with low plasma viral load. Nevertheless, in accordance with the results reported by Raso et al, the correlations in our subgroup analyses were somewhat stronger in patients with a low CD4 nadir, suggesting that severity of immune depression may play some role in the strength of the correlations. We limited our exploratory subgroup analyses to univariable correlations, because the intent of our response to Raso et al is not to assess the determinants of individual locomotor test results but to contribute to the definition of appropriate tests to use for locomotor evaluation in HIV-infected patients.
In the general population, mechanisms of poor physical performance are often complex and multifactorial. As other factors such as muscle power may explain the performance in physical performance and in functional tasks, it has been postulated that the use of grip strength measurements alone is not sufficient.13,14 Moreover, it has been shown in elderly persons that the relation between muscle strength and functional performance is not linear and that an association may only become evident when the subjects reach a critical level of muscle weakness.15 We thus hypothesize that this critical level is not reached in a population of patients with a median age of 50 years and well-controlled HIV disease.
In conclusion, although poor functional performance is highly prevalent in our HIV-infected population, as previously reported,2 our results indicate that grip strength measurements are not an adequate substitute for functional performance tests in HIV-infected patients with well-controlled HIV disease.
The authors C. Lewden who initiated this work, the other members of the GECSA-COGLOC Study Group, and the investigators and patients who participated in the study.
Members of the GECSA-COGLOC Study Group: M. Allard, H. Amieva, M. Auriacombe, S. Auriacombe, E. Bestaven, F. Bonnet, M. Brault, M. Bruyand, G. Catheline, G. Chêne, G. Coldefy, F. Dabis, J.-F. Dartigues, F.-A. Dauchy, S. Delveaux, C. Dufouil, P. Dehail, C. Greib, C. Lewden, J. Macua, F. Marquant, F. Matharan, P. Mercié, C. Milien, P. Morlat, N. Raoux, and L. Richert. The composition of the Groupe d’Epidémiologie Clinique du SIDA en Aquitaine (GECSA) is available at: http://gecsa.isped.u-bordeaux2.fr/Presentation.aspx.
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