Preoperative handgrip strength and physical activity level in association with length of stay after coronary artery bypass grafting

Abstract

BACKGROUND

Coronary artery bypass grafting (CABG) reduces morbidity and mortality in coronary artery disease, but postoperative complications may prolong the length of hospital stay (LoS). Previous studies have reported associations between physical activity level (PAL), handgrip strength (HGS), postoperative complications, and LoS. However, evidence directly examining the relationship between preoperative PAL or HGS and LoS remains limited, particularly in small exploratory cohorts.

AIM

To explore the potential association between preoperative PAL and HGS and postoperative LoS in patients undergoing CABG.

METHODS

This retrospective exploratory study analyzed medical records of CABG patients treated at Dr. Hasan Sadikin General Hospital, Bandung, Indonesia, between October 2023 and March 2024. Preoperative PAL was assessed using the Global Physical Activity Questionnaire, and HGS was measured in both hands. Patients with complete PAL, HGS, and LoS data were included (n = 27). Associations were analyzed using Spearman correlation for HGS and the Mann-Whitney U test for PAL, considering the limited sample size.

RESULTS

No statistically significant associations were observed between LoS and right-hand HGS (P = 0.537), left-hand HGS (P = 0.536), or total HGS (P = 0.436). PAL was also not significantly associated with LoS (P = 0.174), although patients with moderate PAL had a numerically shorter LoS.

CONCLUSION

In this study, no clear association was found between preoperative HGS or PAL and postoperative LoS following CABG. These findings should be interpreted as hypothesis-generating. Larger prospective studies are warranted.

Key Words: Coronary artery bypass; Coronary artery disease; Hand strength; Length of stay; Postoperative complications

Core Tip: Preoperative functional status has been proposed as a modifiable factor of postoperative recovery after coronary artery bypass grafting. Handgrip strength and physical activity level (PAL) are simple, low-cost measures reflecting muscle strength and functional reserve. In this article, neither preoperative handgrip strength nor PAL was significantly associated with postoperative length of hospital stay (LoS) after coronary artery bypass grafting. Although patients with moderate PAL showed a numerically shorter LoS, this finding was not statistically significant. These results highlight the multifactorial nature of postoperative LoS, predominantly driven by perioperative complications, and prospective studies integrating functional, clinical, and postoperative recovery outcomes are needed.

INTRODUCTION

Cardiovascular disease (CVD) continues to be the predominant cause of mortality worldwide, with an estimated 19.4 million deaths reported in 2021, rising to 19.8 million in 2022. These figures correspond to roughly one-third of all deaths globally, with a disproportionate burden borne by low- and middle-income countries and approximately 85% attributable to heart attacks and strokes. Coronary artery disease (CAD), a major subtype of CVD, affects an estimated 254 million people worldwide and was responsible for nearly 9 million deaths in 2021, highlighting its substantial contribution to global cardiovascular mortality[1,2]. In Southeast Asia, CAD represents a significant and growing component of the CVD burden, characterized by high prevalence, mortality, and disability-adjusted life years, with an increasing trend since 1990 largely driven by metabolic and environmental risk factors[3]. In Indonesia, CAD represents a major contributor to mortality and disability attributable to CVD, with steadily rising morbidity and mortality, placing the country among those with the highest CAD burden in the region[4].

Coronary artery bypass grafting (CABG) is a standard surgical intervention for patients with multivessel or anatomically complex CAD, demonstrating an excellent safety profile, with in-hospital mortality below 2.1% and a 30-day mortality rate of only 0.3% in the contemporary era[5]. In addition, CABG provides long-term survival benefits in patients with three-vessel disease and preserved ejection fraction, having been shown to achieve survival outcomes that are superior to those of age- and sex-matched individuals in the general population[6]. However, CABG is still associated with considerable postoperative complications, with morbidity rates of approximately 52%-54%, particularly bleeding requiring transfusion (± 47%-49%), prolonged ventilation (± 5%), and pneumonia (± 4%). Other serious complications, such as myocardial infarction, thromboembolism, deep wound infection, and renal failure, each occur in less than 1% of cases. The presence of such complications significantly prolongs the length of hospital stay (LoS), from around 6.3 days without complications to approximately seven days or more, with deep wound infections and sepsis causing the longest LoS extensions (> 17-23 days)[7].

Prolonged LoS after cardiac surgery is primarily influenced by postoperative complications, particularly postoperative pulmonary complications (PPC), and has significant implications for increased resource utilization and healthcare costs. It also serves as a key target in the planning and evaluation of quality improvement efforts[7]. Postoperative complications, particularly stroke, renal failure, pneumonia, blood transfusion, and prolonged ventilation, also have a significant impact on long-term survival, making complication prevention a primary target for improving long-term outcomes after cardiac surgery[8].

Preoperative physical performance measures, such as gait speed, handgrip strength (HGS), and the Timed Up and Go test, are independently associated with the occurrence of PPCs after CABG and can serve as clinical risk predictors. Low HGS independently increases the risk of PPCs, reflecting muscle weakness and frailty, which increase the risk of pneumonia and other PPCs[9]. Prehabilitation, primarily based on physical activity (PA) or exercise, is consistently associated with improved preoperative functional capacity and reduced postoperative complications, particularly PPCs such as atelectasis, with the greatest benefits observed in frail patients or those with age-related muscle impairment. In addition, prehabilitation has the potential to accelerate recovery and positively influence LoS[10,11].

To date, evidence regarding the role of preoperative functional factors, such as HGS and PA level (PAL), on postoperative LoS, particularly following CABG, remains limited and inconclusive. Most available studies are derived from broader cardiac surgical populations or other major surgical procedures, suggesting a potential association between preoperative functional status and postoperative recovery, including LoS. However, findings related to preoperative PAL are inconsistent, and evidence specifically examining the direct relationship between preoperative HGS and PAL with LoS after CABG remains limited[12-18].

Therefore, given the limited evidence directly examining the relationship between preoperative functional status and postoperative LoS in patients undergoing CABG, this study aimed to explore the potential associations between preoperative PAL and HGS with postoperative LoS. By focusing on readily obtainable preoperative functional measures, this exploratory analysis may inform the design of future prospective studies and hypothesis-driven investigations of preoperative functional status in patients with CABG.

MATERIALS AND METHODS

Study design and setting

This retrospective exploratory study was designed as a pilot analysis and employed an observational analytic design with a cross-sectional approach. The study was conducted at Dr. Hasan Sadikin General Hospital (RSHS), Bandung, Indonesia, a tertiary referral hospital. It analyzed secondary data obtained from medical records of patients who underwent CABG and were managed by the Department of Physical and Rehabilitation Medicine. The study period covered October 1, 2023, to March 31, 2024, including the entire in-hospital perioperative course from preoperative admission until hospital discharge.

Study population and eligibility criteria

The study included adult patients (≥ 18 years) who underwent isolated CABG surgery at RSHS during the study period. Inclusion criteria were adult post-CABG surgery during the study period, availability of documented preoperative PAL assessed using the Global Physical Activity Questionnaire (GPAQ), and availability of preoperative HGS measurements for at least one hand. Exclusion criteria were patients who died intraoperatively or before completing the postoperative hospitalization period, patients with incomplete or missing data on LoS, HGS, or PA, and patients with musculoskeletal or neurological conditions that could interfere with accurate HGS measurement (e.g., severe arthritis, trigger finger, contractures). Patients who did not meet the eligibility criteria were excluded from the analysis.

Sample size and sampling technique

A retrospective consecutive sampling approach with predefined eligibility criteria was applied. During the study period, 93 CABG patients were identified from medical records. Of these, 28 patients had complete length-of-stay data, and one patient was excluded due to the inability to measure HGS, resulting in a final analytical sample of 27 patients. No a priori sample size calculation was performed due to the exploratory nature of the study.

Variables and operational definitions

Defined as the number of days from the date of CABG surgery until hospital discharge, the primary outcome was LoS, and was selected as a pragmatic and clinically relevant outcome reflecting in-hospital postoperative recovery. Independent variables were HGS (measured in kg for the right hand, left hand, and total HGS and treated as continuous variables) and PAL (categorized as low, moderate, or high according to GPAQ scoring guidelines and treated as an ordinal variable). Baseline patient characteristics were described, including demographic variables (age, sex, body mass index, and educational level) and CVD risk factors (smoking status, hypertension, dyslipidemia, and diabetes mellitus).

Measurement of HGS and PAL

HGS was measured using a Jamar hydraulic hand dynamometer, a device recommended and widely regarded as the gold standard for grip strength assessment, which provides isometric grip strength measurements recorded in kilograms with high intra-device reliability[19-21]. PAL was assessed using the GPAQ developed by the World Health Organization. The GPAQ evaluates PA across three domains: Occupational, transportation, recreational activities, and sedentary behavior. Based on total metabolic equivalent-minutes per week, PA was classified into low, moderate, or high levels according to World Health Organization guidelines[22].

Data collection procedures

All study variables were extracted from patients’ medical records using a standardized data extraction form. Data were anonymized before analysis to ensure confidentiality. The investigators did not intervene in patient management, and all measurements were performed as part of routine clinical care.

Statistical analysis

Statistical analyses were performed using IBM SPSS Statistics version 27. Continuous variables were described using appropriate summary measures according to their distribution, while categorical variables were expressed as n (%). The association between HGS (right, left, and total; continuous variables) and LoS was assessed using Spearman’s rank correlation test. The association between PAL (ordinal variable) and LoS was analyzed using the Mann-Whitney U test, as PAL comprised two analyzable categories (low and moderate). Given the limited sample size, multivariable regression analysis was not performed due to the substantial risk of overfitting. All statistical tests were two-tailed, with statistical significance defined as a P value < 0.05.

Ethical considerations

The study was performed in compliance with internationally recognized ethical standards for human research. Approval was granted by the Ethics Committee of RSHS (No. 203/UN6.KEP/EC/2024). Given the retrospective design and the use of fully anonymized secondary data, the need for informed consent was waived.

RESULTS

Participant characteristics

The study population consisted predominantly of older adults and was largely male. Most participants had body mass index values within the normal to overweight range, while underweight and obesity were uncommon. A substantial proportion of patients reported a history of smoking, and more than half had hypertension; dyslipidemia and diabetes mellitus were less frequently observed. HGS demonstrated moderate inter-individual variability, with generally higher values observed in the dominant hand. The majority of participants exhibited low preoperative PAL, and none were classified as having high PAL. Postoperative LoS varied considerably among patients, reflecting heterogeneity in postoperative recovery (Table 1).

Table 1 Baseline characteristics of patients undergoing coronary artery bypass grafting (n = 27), n (%).

Variable	Value
Age (years)
mean ± SD	60.56 ± 8.57
Sex
Male	22 (81.5)
Female	5 (18.5)
Body weight (kg)
mean ± SD	65.88 ± 11.35
Median (range)	69 (40-86.7)
Body mass index
Underweight (< 18.5 kg/m2)	1 (3.7)
Normal (18.5-24.9 kg/m2)	12 (44.4)
Overweight (25.0-29.9 kg/m2)	13 (48.1)
Obese (≥ 30 kg/m2)	1 (3.7)
Smoking history
Yes	20 (74.1)
No	7 (25.9)
Dyslipidemia
Yes	10 (37.0)
No	17 (63.0)
Hypertension
Yes	15 (55.6)
No	12 (44.4)
Diabetes mellitus
Yes	5 (18.5)
No	22 (81.5)
Handgrip strength - left (kg)
Median (range)	12 (6-30)
Handgrip strength - right (kg)
Median (range)	15 (8-35)
Total handgrip strength (kg)
Median (range)	26 (14-65)
Physical activity level (GPAQ)
Low	18 (66.7)
Moderate	9 (33.3)
High	0 (0)
Length of hospital stay (days)
Median (range)	9 (4-27)

Handgrip strength was assessed using the Jamar dynamometer, and physical activity level was evaluated using the Global Physical Activity Questionnaire. GPAQ: Global Physical Activity Questionnaire.

Association between HGS and LoS

Spearman’s rank correlation analysis demonstrated no statistically significant associations between preoperative HGS (right hand, left hand, or total HGS) and postoperative LoS following CABG (all P values > 0.05) (Table 2).

Table 2 Correlation between handgrip strength and length of stay.

Variable	Ρco-efficient value (Spearman)	P value
Right HGS	0.12	0.537
Left HGS	0.14	0.536
Total HGS	0.15	0.436

HGS: Handgrip strength.

Association between PAL and LoS

Patients with moderate preoperative PAL exhibited a shorter median postoperative LoS compared with those with low PAL; however, this difference did not reach statistical significance (Mann-Whitney U test, P = 0.174) (Table 3).

Table 3 Association between physical activity level and length of stay.

Physical activity level	n	Length of stay (median, range in days)
Low	18	9 (4-27)
Moderate	9	8 (5-14)
Mann-Whitney U test	-	P = 0.174

Values are presented as median (range). The association between physical activity level and length of hospital stay was analyzed using the Mann-Whitney U test.

DISCUSSION

Main interpretation of the findings

This retrospective exploratory analysis was designed as a pilot study to assess the feasibility and direction of associations between preoperative functional measures and postoperative LoS after CABG. In this study, preoperative HGS and PAL were not significantly associated with LoS after CABG. Although patients with moderate PAL tended to have shorter LoS than those with low PAL, this difference did not reach statistical significance. Given the limited sample size and exploratory nature of the analysis, these findings should be interpreted with caution and cannot be considered definitive evidence of the absence of an association. Rather than indicating a lack of clinical relevance of preoperative functional status, the present results suggest that its influence on early postoperative LoS may be modest and potentially masked by stronger perioperative determinants. In cardiac surgical populations, traditional clinical and perioperative risk factors, such as advanced age, preexisting renal dysfunction, atrial fibrillation, and higher perioperative risk scores like the European System for Cardiac Operative Risk Evaluation, have been consistently identified as significant predictors of prolonged postoperative and intensive care unit LoS, underscoring the multifactorial determinants of recovery beyond functional measures alone[23,24]. These findings further emphasize the multifactorial nature of LoS and highlight the challenge of isolating the independent contribution of preoperative functional measures in small observational cohorts.

Severe underpowering and selection bias

The final analytical sample of 27 patients represents a critically underpowered cohort for detecting small-to-moderate associations between preoperative functional measures and postoperative LoS. Of the 93 patients undergoing CABG during the study period, a substantial proportion were excluded due to incomplete documentation of preoperative HGS and PAL, raising the possibility of selection bias. As a consequence, the absence of statistically significant associations in this study should not be interpreted as evidence of no effect, but rather as a reflection of limited statistical power and methodological constraints inherent to this retrospective exploratory design. Given the limited number of outcome events, multivariable modeling was not feasible without a high risk of overfitting and was therefore not pursued.

HGS

HGS has been widely recognized as a surrogate marker of overall functional status and an important prognostic indicator in cardiovascular populations. Large population-based studies and meta-analyses have demonstrated that lower HGS is associated with increased all-cause and cardiovascular mortality, including among patients with CAD and older adults[15,25].

In the context of cardiac surgery, prospective studies have further shown that lower preoperative HGS is associated with adverse postoperative outcomes, including prolonged mechanical ventilation, longer intensive care unit (ICU) stay, delayed ambulation, and impaired functional recovery[12,26,27]. However, evidence specifically evaluating the direct relationship between preoperative HGS and postoperative LoS after CABG remains limited and heterogeneous[13].

In the present cohort, the absence of a significant association between preoperative HGS and postoperative LoS may be explained by several factors. First, the sample size was critically small and likely underpowered to detect clinically meaningful associations, particularly given the modest effect sizes reported in prior studies. Second, the distribution of HGS values was relatively narrow, with most patients clustered within low-to-moderate strength categories. Such a restricted biological gradient may attenuate statistical associations, especially in unadjusted analyses[13,15,26]. Moreover, emerging evidence suggests that HGS primarily reflects underlying functional reserve and is more consistently associated with recovery-related outcomes, such as early ambulation and longer-term prognosis, rather than early hospitalization metrics like LoS[12,27,28]. Given the dominant influence of acute perioperative events and postoperative complications on LoS after CABG, the independent contribution of preoperative HGS to short-term hospital stay is likely context-dependent and relatively modest.

PAL

PAL is a well-established determinant of cardiovascular health and long-term outcomes. Systematic reviews and meta-analyses have consistently demonstrated that higher PAL is associated with reduced cardiovascular morbidity and mortality, as well as improved quality of life (QoL) in patients with CVD[29,30].

Among patients undergoing CABG, however, evidence regarding the relationship between preoperative PAL and short-term outcomes such as LoS remains inconclusive. A prospective pilot study demonstrated that preoperative PAL could be reliably assessed but was not consistently associated with early postoperative clinical outcomes[31]. Similarly, a systematic review reported mixed findings, with some studies showing shorter LoS among more physically active patients and others reporting no significant association[17].

In the current study, although not statistically significant, the observed trend toward shorter LoS among patients with moderate PAL is hypothesis-generating rather than confirmatory. This trend should not be overstated and may reflect residual confounding or random variation due to limited statistical power. Consistent with prior evidence, preoperative PAL appears to be more robustly associated with longer-term outcomes, such as mortality, QoL, and functional recovery, than with acute hospitalization metrics after CABG[17,29,30]. Importantly, the use of categorical PAL classification (low vs moderate) rather than continuous metabolic equivalent-based values may have further limited sensitivity to detect dose-response relationships. As suggested by previous studies, the effect of preoperative PA on early postoperative recovery may be indirect, operating through reduced complications, enhanced physiological reserve, and faster functional regain, rather than directly shortening LoS[28,31,32].

Influence of perioperative factors

The lack of significant associations between HGS, PAL, and LoS observed in this study may be explained by the dominant influence of acute perioperative and postoperative factors inherent to CABG surgery. Postoperative LoS is strongly affected by ICU duration, length of mechanical ventilation, PPC, bleeding, hemodynamic instability, and infectious events, all of which have been shown to substantially prolong hospitalization[7,28,32,33].

Because these variables were not incorporated into a multivariable analytical model, residual confounding cannot be excluded. In addition, non-clinical factors, such as institutional discharge policies, ICU bed availability, and practice variation, may further obscure associations between preoperative functional status and LoS[34,35].

Clinical and research implications

The absence of statistically significant associations with LoS should not be interpreted as evidence that HGS and PAL lack clinical relevance. Rather, these measures may be more informative for predicting other clinically meaningful outcomes, including postoperative complications, delayed mobilization, functional recovery, QoL, and longer-term prognosis[26,36]. Recent systematic reviews and meta-analyses suggest that structured exercise-based prehabilitation programs may improve postoperative functional capacity and potentially reduce LoS after cardiac surgery[37]. These findings support the concept that preoperative functional status is a modifiable factor, even if its isolated effect on short-term LoS is difficult to detect in small observational studies.

Strengths and limitations of the study

The strengths of this study include the use of standardized and validated instruments, namely the Jamar dynamometer for HGS and the GPAQ for PAL, as well as data derived from routine clinical practice at a tertiary referral center. However, several important limitations must be emphasized. The study was critically underpowered, with substantial attrition from the initially identified cohort, raising concerns about selection bias. The retrospective design, reliance on self-reported PAL, absence of a priori sample size calculation, and lack of multivariable adjustment further restrict causal inference. Accordingly, this study should be regarded as a pilot or exploratory analysis. Future studies should employ prospective designs with larger and more representative samples, incorporate objective PA measurements (e.g., accelerometry), include detailed perioperative and complication data, and apply multivariable or causal modeling approaches. Outcomes beyond LoS, such as ICU stay, prolonged ventilation, delayed ambulation, and functional recovery, may be more sensitive endpoints for evaluating the clinical impact of preoperative functional status in CABG populations.

CONCLUSION

In this small retrospective exploratory cohort of patients undergoing CABG, preoperative PAL and HGS were not independently associated with postoperative LoS. Although patients with moderate PAL demonstrated a numerically shorter LoS, this difference did not reach statistical significance and should be interpreted cautiously. Given the severe underpowering, retrospective design, and the multifactorial nature of postoperative LoS, largely driven by perioperative and postoperative factors, these findings should be regarded as hypothesis-generating. Larger prospective studies incorporating postoperative complications, functional recovery measures, and multivariable analytical approaches are required before definitive conclusions can be drawn.

ACKNOWLEDGEMENTS

The authors would like to express their sincere gratitude to Dr. Hasan Sadikin General Hospital, Bandung, Indonesia, for granting permission to conduct this study and for providing access to the required clinical data. The authors also acknowledge the Faculty of Medicine, Universitas Padjadjaran, for providing the academic opportunity to conduct this research as part of undergraduate medical education.