Association Between Serum Pyridoxal 5'-Phosphate and Frailty Risk in Community-Dwelling Older Japanese Adults

Pyridoxal 5'-phosphate (PLP) is the coenzyme form of vitamin B₆. PLP is essential for amino acid metabolism, protein turnover, and neurotransmitter synthesis. Plasma or serum PLP concentration is used as an indicator of vitamin B₆ 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.

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.

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.

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.