This study is based on a look back at information that was gathered in the future. The purpose of this study was to examine how frailty and sarcopenia affected recovery from lumbar spine surgery. Degenerative spine disease is a prevalent surgical problem among the elderly. As people age, their physiological reserve decreases, leading to symptoms like weakness and fatigue after elective spine surgery. How these factors affect patient-reported outcomes  (PROs) is mostly unknown.  Those who were above 70 and had planned procedures on their lumbar spine were considered. Frailty was measured using the modified 5-item frailty index (mFI-5). The total psoas index was used to define sarcopenia, calculated by dividing the total psoas area in the middle of the lumbar spine by the VB area (L3-TPA/VB). The North American Spine Society (NASS), the Oswestry disability index (ODI), the numeric rating scale for back pain (NRS-BP), the numeric rating scale for leg pain (NRS-LP), and the EuroQual-5D (EQ-5D), at 12 months postoperatively were all used as PROs. Time in the hospital, readmission within 90 days, and the occurrence of complications were some of the clinical outcomes measured. Many different types of regression analyses (both univariate and multivariate) were done. About 448 in all were included. A total psoas index of 1.7±0.5 and a mFI-5 index of 1.6±1.0 were found to be the averages. All PROs showed statistically significant gains between baseline and 12 months (P<0.0001). A Higher mFI-5 index was linked with greater 12-month ODI (P=0.001), lower 12-month EQ-5D (P=0.001), higher NRS-LP (P=0.039), and longer LOS (P=0.007) after controlling for age, BMI, smoking status, levels fused, and baseline PROs. The 12-month PROs and LOS were not correlated with sarcopenia. Sarcopenia and micronutrient deficiencies index-5 (mFI-5) were not related to complications and readmissions within the first 90 days after hospitalization. After having elective surgery on their lumbar spine, elderly patients report considerable improvements in PROs. Lower ODI, EQ-5D, and NRS-LP scores at 12 months after surgery and a longer length of stay in the hospital were all related to frailty. Preoperative counseling with the mFI-5 is recommended for patients undergoing elective lumbar spine surgery to discuss realistic expectations for disability, health-related quality of life, and leg discomfort. This was provided by third-level evidence.