Gait speed has been widely accepted as an indicator of health risk in older adults and is regarded as the sixth vital sign[8, 9]. It has good predictive value for mortality, cardiovascular diseases, and cancer. Several mechanisms explain the link between reduced gait speed and the risk of adverse outcomes: (1) Muscular factors, including reduced motor units, impaired muscle activation, replacement of type I fibers by type II fibers, leading to decreased contraction speed and strength; (2) Neurological factors, such as decreased skin sensitivity, reduced nerve conduction velocity and reaction time, reduced gray matter volume with functional brain damage, and white matter lesions; (3) Numerous inflammatory markers are also associated with sarcopenia and muscle strength loss and may independently predict decreased gait speed and progression to severe gait impairment[10].
This study shows that age, height, and weight are associated with reduced gait speed. This is consistent with Jennifer A. Schrack's view that walking speed decreases with age, and considering that increases in age, weight, and BMI lead to higher energy costs, resulting in reduced gait speed[11, 12]. The effect of height on gait speed is generally positive; as height and stride length increase, the walking speed is faster at the same walking frequency. However, some studies suggest that the advantage brought by height diminishes with age[13]. Univariate analysis shows that education level is associated with reduced gait speed, but multivariate analysis did not find a significant correlation. Alexis Elbaz et al. believe that participants with higher education levels generally have better physical performance[14]. Since this study did not consider participants' occupations, family income, and other factors, it cannot determine the correlation between education level and reduced gait speed.
This study found that marital status is associated with gait speed, with married participants having a lower risk of reduced gait speed compared to non-married participants (divorced, widowed, unmarried). This indicates that social support is related to gait speed decline, consistent with the findings of Chava Pollak et al.[15, 16]. The study also found differences in caregiving arrangements, with those receiving care from a nanny or others having a higher risk of reduced gait speed compared to those cared for by their spouses. Considering the mutual influence between caregiving and reduced gait speed, participants with reduced gait speed are more likely to receive care from a nanny or others.
There was no significant correlation between living arrangements and reduced gait speed. According to a survey on elderly living preferences in Wuhan, about 63.4% of elderly individuals prefer to age at home, which is similar to the findings of this study[17].The study found that participants who drank occasionally had the best gait speed performance. However, there is no consensus on whether alcohol consumption is beneficial[18].
This study indicates that blood urea nitrogen (BUN), low-density lipoprotein (LDL), Chinese visceral obesity index (CVI), cardiometabolic index (CMI), and systemic immune-inflammation index (SII) are all associated with a decrease in walking speed.BUN levels are negatively correlated with the risk of reduced walking speed. Under stable conditions, BUN levels are primarily related to dietary protein intake and serve as a protective factor against reduced walking speed[19].
LDL levels are negatively correlated with decreased walking speed. LDL is responsible for transporting triglycerides to peripheral tissues, which can increase energy costs and slow down the decline in muscle strength. The current participants' LDL levels are 2.66 ± 0.77 and 2.42 ± 0.70 mmol/L, which overlap significantly with the recommended blood lipid levels[20]. Considering the impact of blood lipids on cardiovascular diseases, further research is needed to balance these factors reasonably.
The Chinese Visceral Obesity Index (CVI) is derived from the visceral obesity index and has good consistency with visceral fat in Asians[21]. CMI integrates characteristics of dyslipidemia and abdominal obesity and is considered a measure of visceral obesity[22]. Both are negatively correlated with decreased walking speed, indicating that lipids primarily protect against muscle strength decline. However, this differs from Keita Kinoshita et al.'s view that abdominal fat increases with age, significantly increasing the risk of reduced walking speed[22].
The Systemic Immune-Inflammation Index (SII) is an inflammatory marker, and muscle aging is related to chronic inflammation[23]. For instance, interleukin-6 levels are associated with walking speed and can benefit from walking exercise[23].The plotted ROC curve shows that BUN, CVI, and SII perform better than LDL and CMI.Based on this, we can make the following hypotheses: 1. Inflammation is the primary cause of reduced muscle strength in the elderly, followed by insufficient intake of protein and lipids, leading to further muscle atrophy; 2. Inflammation may mediate muscle atrophy caused by insufficient protein and lipid intake.