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.

Study design: A prospective cohort study.

Purpose: 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.

Overview of literature: 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.

Methods: 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.

Results: 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).

Conclusions: 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.