A prospective study on age-specific normative values of the prognostic nutritional index and the effects of malnutrition on spinal alignment using health checkup data of elderly residents.

Abstract

A prospective cohort study. To determine the age-specific normative values of the prognostic nutritional index (PNI) among elderly residents in Japan and explore the relationship between malnutrition and spinal alignment. Nutritional status affects postoperative recovery, with malnourished patients often experiencing severe postoperative complications. PNI is a known nutritional indicator based on serological value; however, there is a dearth of age-specific normative values for PNI, with even less research on the impact of malnutrition on spinal alignment. We included 237 participants from a 2-yearly resident health checkup conducted in Toei, Aichi, Japan. Participants underwent blood tests and whole-spine standing radiography, and were stratified based on age (60s, 70s, and 80s) and sex to determine age-specific normative PNI values. Additionally, participants were categorized into a lower PNI (PNI <50) or higher PNI (PNI ≥50) group to compare spinal alignment. The average PNI values for different age groups were: 60s: males (n=13): 50.7, females (n=31): 50.9; 70s: males (n=55): 50.3, females (n=57): 50.1; 80s: males (n=28): 49.1, females (n=53): 48.3. For females, the radiographic spinal alignment parameters were comparable between the lower and higher PNI groups; however, in males, significant differences were noted for pelvic tilt (20° vs. 16°, p=0.020), lumbar lordosis (35° vs. 44°, p<0.001), and pelvic incidence minus lumbar lordosis (10° vs. 4°, p=0.013). Malnutrition in males negatively impacts their lumbar-pelvic alignment. While the normative PNI value decreases with age, the two variables show a very weak correlation.