The finding: 
This study demonstrates that accelerated biological aging, as measured by PhenoAge, is associated with increased risk of both suicide attempts and suicidal ideation in a large (n = 124,529), middle-aged (average age = 55.9 years) population. Readers should note that the PhenoAge in this study is a clinical biomarker-based estimate of age, based on albumin, alkaline phosphatase, creatinine, glucose, C-reactive protein, lymphocyte percentage, mean cell volume, red cell distribution width, and white blood cell count, and chronological age. Even after adjusting for demographic variables, substance use, and medical diagnoses, individuals in the highest (“biologically oldest”) quartile of PhenoAge had a 21.8% higher risk of suicide attempt and a 12.5% higher risk for suicidal ideation when compared to the lowest (“biologically youngest”) quartile. Interactions were noted with specific subgroups, with higher PhenoAge predicting suicide attempts in males and younger individuals (age < 60), and higher PhenoAge predicting suicidal ideation in those with physical or psychiatric disorders, low levels of physical activity, those without a college degree, and the unemployed.

Strength and weaknesses:
This study has significant strengths, including the use of a well-characterized cohort (the UK Biobank) with a large number of events (2718 suicide attempts and 5207 cases of suicidal ideation), which enhances generalizability and provides significant power. The use of an aging biomarker based on clinical laboratory values (PhenoAge) is also a strength, as these are often available in clinical populations, unlike epigenetic aging measures. Consideration of moderators such as sex is also an important and contributes to the interpretability of the findings. Limitations include the lack of adjustment for multiple comparisons given many models were tested, increasing the risk of false positives. The data are also cross-sectional, and the effect sizes, while statistically significant, are unlikely to be useful in clinical practice as is.

Relevance:
These findings underscore the importance of health and aging in suicide risk. As CL psychiatrists are often caring for individuals with complex and intersecting medical and psychiatric diagnoses, reinforcement of the protective nature of healthy aging (and the detrimental effects of accelerated aging) on suicide risk may help with both risk assessment and identification of modifiable risk factors. While these data are cross-sectional and thus causality cannot be tested, they suggest the possibility that interventions that improve lab tests such as CRP, albumin, creatinine, and glucose may also decrease suicide risk.