Phthalate exposure and its impact on mental health risk in the elderly Thai population

Phthalates, ubiquitous environmental contaminants, are widely used in daily life. Although their adverse health effects across developmental stages have been well-documented, their impact on elderly populations remains unexplored. This study investigated the association between phthalate exposure and mental health issues (depression, anxiety, and stress). A community-based cross-sectional study was conducted among 688 individuals aged ≥ 60 years in Thailand. Phthalate exposure was assessed using five urinary phthalate metabolites: mono(2-ethylhexyl) phthalate (MEHP), monoisobutyl phthalate, mono-n-butyl phthalate (MnBP), monoethyl phthalate, and monomethyl phthalate. Mental health status was evaluated using the Depression Anxiety Stress Scales (DASS-21), a self-administered questionnaire that assesses depression, anxiety, and stress, along with demographic data. Binary logistic regression adjusted for potential confounders was used to analyze associations with mental health risks. The detection rates for the phthalate metabolites ranged between 31.83 and 96.08%, with MEHP being most frequently detected. Depression emerged as the most prevalent mental health condition. Among healthy participants, those in the highest tertile of urinary MEHP and MnBP levels exhibited significantly increased odds of anxiety, with adjusted odds ratios 3.13 (95% CI 1.37-7.12) and 2.28 (95% CI 1.03-5.06), respectively. Both metabolites exhibited a dose-response relationship (p-for-trend = 0.002 and 0.034, respectively). The number needed to harm was 5.66 for MEHP and 8.09 for MnBP. Associations were not observed in individuals with underlying chronic diseases. Furthermore, no association with depression or stress was observed. In conclusion, exposure to both high- and low-molecular-weight phthalates was associated with an increased risk of anxiety among healthy older adults. However, causal inferences were not confirmed owing to the study design. Longitudinal research is warranted to clarify the underlying mechanisms and inform mental health surveillance for older individuals.