Sarcopenia parameters in active older adults – an eight-year longitudinal study

**Background:** Sarcopenia is a common skeletal muscle disorder in older adults, with prevalence ranging from 10% to 27% in those over 60. Physical inactivity and sedentary behavior are major modifiable risk factors. While cross-sectional studies show that regular physical activity (PA) reduces sarcopenia risk, longitudinal data in active older adults are scarce. This study aimed to evaluate changes in sarcopenia parameters over eight years in a cohort of active older adults and to compare their performance with reference populations.

**Methods:** This observational longitudinal cohort study included 52 active older adults (22 men, 30 women; mean age 68.3 ± 5.4 years at baseline) who participated in the PANGeA study in Koper, Slovenia, in 2013 and returned for follow-up in 2021. Inclusion criteria were age 60–80 years, ability to walk 2 km independently, and no severe cognitive decline (MoCA ≥10). Exclusion criteria included acute illness, recent hospitalization, insulin-treated diabetes, or medications other than metformin. At both time points, sarcopenia parameters were assessed: muscle strength via handgrip test (Yamar dynamometer), skeletal muscle mass index (SMI) calculated from appendicular skeletal muscle mass estimated using the Lee et al. equation divided by BMI, and physical performance via gait speed (self-selected pace over 4 m). Sarcopenia was classified per EWGSOP2 criteria (probable: low handgrip strength <27 kg men, <16 kg women; sarcopenia: low strength plus low SMI <0.789 men, <0.512 women; severe: low strength, low SMI, and gait speed <0.8 m/s). PA and sedentary behavior (SB) were self-reported using the Global Physical Activity Questionnaire (GPAQ). At follow-up, additional tests were performed: Chair stand test, 30-second chair stand test, Timed Up and Go (TUG), Short Physical Performance Battery (SPPB), and tensiomyography (TMG) of vastus lateralis, biceps femoris, and gastrocnemius medialis. Participants were categorized by HEPA level (≥3000 MET-min/week achieved through planned PA [HEPAP], work [HEPAW], or not achieved [HEPAN]) and by SB (≤4 h/day [SB-L] or >4 h/day [SB-H]). Statistical analyses included paired t-tests, Pearson correlations, mixed linear models adjusted for age, and one-sample t-tests comparing follow-up results with reference values.

**Key Results:** At baseline, no participant met sarcopenia criteria. After eight years, 7 participants (13.5%) had sarcopenia: 4 probable, 2 sarcopenia, 1 severe. All sarcopenia parameters declined significantly: handgrip strength from 35.4 ± 14.9 kg to 31.8 ± 12.2 kg (−10.2%; p < 0.001; Cohen's d = 0.52), SMI from 0.92 ± 0.21 to 0.87 ± 0.22 (−5.4%; p < 0.001; Cohen's d = 1.67), and gait speed from 1.4 ± 0.2 m/s to 1.0 ± 0.2 m/s (−28.6%; p < 0.001; Cohen's d = 0.22). Self-reported PA decreased from 5170 ± 3112 to 3876 ± 2665 MET-min/week (−25.0%; p = 0.030; Cohen's d = 0.44), and SB decreased from 260 ± 115 to 134 ± 75 min/day (−48.5%; p < 0.001; Cohen's d = 1.38). Mixed linear models showed significant time effects for handgrip strength (p < 0.001), SMI (p = 0.004), and gait speed (p < 0.001) in HEPA groups, and for handgrip strength (p = 0.005) and gait speed (p < 0.001) in SB groups, after adjusting for age. No significant group-by-time interactions were found except for SMI between HEPA groups (p = 0.030), with post-hoc differences between HEPAW and HEPAN (p = 0.031). At baseline, PA positively correlated with handgrip strength (r = 0.392, p = 0.006, r² = 15.4%). At follow-up, compared with reference values, men performed better on TUG (6.9 ± 2.0 vs. 9.2 s; p < 0.001; Cohen's d = -1.15) and SPPB (11.3 ± 0.8 vs. 10.2; p < 0.001; Cohen's d = 1.38), and women performed better on Chair stand test (10.3 ± 3.3 vs. 12.2 s; p = 0.005; Cohen's d = -0.58), TUG (7.0 ± 1.4 vs. 9.2 s; p < 0.001; Cohen's d = -1.57), and SPPB (11.2 ± 1.1 vs. 10.2; p < 0.001; Cohen's d = 0.91). TMG showed lower Dm in biceps femoris (4.3 ± 2.8 vs. 5.9 mm; p < 0.001) and vastus lateralis (4.2 ± 1.9 vs. 5.4 mm; p < 0.001) compared with reference values. Sarcopenic participants had lower DmVL than non-sarcopenic (Z = 2.097, p = 0.036). Positive correlations were found between DmVL and SMI (rho = 0.531, p < 0.001), handgrip strength (rho = 0.405, p = 0.004), and gait speed (rho = 0.341, p = 0.015); negative correlations with Chair stand test (rho = -0.359, p = 0.011) and TUG (rho = -0.370, p = 0.008).

**Clinical Implications:** This study demonstrates that even in active older adults who maintain regular PA above recommended levels, significant declines in muscle strength, mass, and physical performance occur over eight years, with a 13.5% incidence of sarcopenia. However, their performance on functional tests (TUG, SPPB, Chair stand) remained superior to reference populations, suggesting that an active lifestyle may delay functional decline and preserve a higher baseline, potentially reducing disability risk. The lack of difference between HEPA groups (work vs. planned PA) implies that total PA volume, rather than type, is key. The unexpected decrease in SB over time may reflect pandemic-related changes or reporting bias. TMG findings indicate that sarcopenia is associated with reduced muscle contractility (lower Dm) without changes in contraction time (Tc), suggesting preserved fiber-type proportions but loss of contractile elements. TMG may serve as a non-invasive biomarker for muscle quality in sarcopenia assessment. Limitations include small sample size (52 participants, 35% response rate), self-reported PA/SB, estimated muscle mass via equation, and lack of mid-term assessments. The study was underpowered for some subgroup analyses. Nonetheless, these findings support public health strategies promoting lifelong PA to mitigate sarcopenia, as emphasized by the WHO Decade of Healthy Ageing and Slovenia's Longevity Strategy.