Association of low alanine aminotransferase with loss of independence or death: A 5-year population-based cohort study

Background and Aim Alanine aminotransferase (ALT) is an important enzyme for amino acid metabolism and gluconeogenesis, and low ALT is an indicator of vitamin B6 deficiency. However, it is unknown whether individuals with low ALT are likely to develop loss of independence (LOI) or death. We investigated the association of low ALT with LOI or death in the elderly. Methods Between 2008 and 2010, 2,484 elderly individuals (>= 65 years old) without functional dependency from the Locomotive Syndrome and Health Outcomes in the Aizu Cohort Study were enrolled. Based on baseline ALT values, the participants were divided into the following groups: ALT < 10 (n = 73), 10-20 (n = 1,372), 20-30 (reference, n = 734), 30-40 (n = 201), and >= 40 (n = 104) U/L groups. LOI was defined as requiring complete support for basic activities of daily living, which is care levels 3-5 in Japanese long-term care insurance certifications. The hazard ratios of LOI or death were estimated by Cox proportional hazard models adjusted for potential confounders. Results During the median follow-up period of 5.75 (interquartile range 4.85-5.83) years, LOI or death occurred in 195 participants (7.85%). Compared with ALT 20-30 U/L, low ALT was associated with LOI or death (multivariable adjusted hazard ratios [95% confidence intervals]: 3.02 [1.57-5.81] and 1.55 [1.07-2.24] in ALT < 10 and 10-20 U/L groups, respectively), while high ALT was not (1.29 [0.72-2.31] and 1.49 [0.68-3.25] in ALT 30-40 and >= 40 U/L groups, respectively). Conclusions Clinicians should be aware of not only high ALT, indicating liver injury, but also low ALT associated with LOI or death.