Association Between Serum Pyridoxal 5′‐Phosphate and Frailty Risk in Community‐Dwelling Older Japanese Adults

Background Pyridoxal 5′‐phosphate (PLP) is the coenzyme form of vitamin B 6 . PLP is essential for amino acid metabolism, protein turnover, and neurotransmitter synthesis. Plasma or serum PLP concentration is used as an indicator of vitamin B 6 status. A deficiency in PLP may be a risk factor for frailty. While previous cross‐sectional studies have associated low plasma or serum PLP levels with frailty, this association has not yet been examined in older Japanese adults. Methods We analyzed data from 419 community‐dwelling individuals aged ≥ 65 years in Tarumizu City, Kagoshima, Japan. Participants with relevant medical histories, missing data, or extreme values were excluded. Frailty was assessed using J‐CHS criteria. Serum PLP concentrations were divided into quartiles (Q1–Q4). Logistic regression was used to estimate the Odds ratios (ORs) for pre‐frailty/frailty after adjusting for demographic, lifestyle, and clinical factors. Results Pre‐frailty/frailty prevalence was 62%, 40%, 57%, and 57% in Q1–Q4, respectively. The proportion of pre‐frailty/frailty was the lowest in Q2. Compared to Q2, adjusted ORs were 1.94 (95% CI: 1.06–3.59; p = 0.033) in Q1, 1.68 (95% CI: 0.93–3.07; p = 0.089) in Q3, and 1.86 (95% CI: 1.01–3.47; p = 0.047) in Q4. Conclusion The relationship between PLP levels and pre‐frailty/frailty was found to be non‐linear. The lowest prevalence was observed in Q2, whereas both low and high PLP levels were associated with increased ORs of pre‐frailty/frailty. Further prospective studies are needed to clarify the causal relationship in older Japanese adults.