Supplementary Material for: Salivary Testosterone Concentration and Cognitive Impairment among Japanese Older Adults in the Toon Health Study

Introduction: As the number of people with mild cognitive impairment (MCI) increases, modifiable risk factors, such as stress and an unhealthy lifestyle, and preventative measures are gaining interest. However, evidence for an association between potential biomarkers of such risk factors and MCI is limited. The study aimed to investigate the association between the salivary testosterone concentration and MCI in Japanese community-dwelling older adults. Methods: This cross-sectional study involved 359 participants (159 men and 200 women) aged 60 years and over. MCI was evaluated using the Japanese version of the Montreal Cognitive Assessment; a score <26 was deemed indicative of MCI. A saliva sample was collected after the patient chewed sugar-free gum for 5 min in the morning, and the salivary testosterone concentrations were assayed. A modified Poisson regression model was used to examine the association between the salivary testosterone concentration and MCI after adjusting for age, body mass index, hypertension, diabetes mellitus, alcohol intake, smoking status, physical activity, sleep hours and age at menopause (women only). Results: For women, the multivariable-adjusted prevalence ratio (PR; 95% confidence interval [CI]) of MCI for the highest-quartile group of salivary testosterone concentrations compared with the lowest-quartile group was 0.52 (0.26, 1.04), and the multivariable-adjusted PR (95% CI) for 1-standard deviation increments of log-transformed salivary testosterone concentrations was 0.74 (0.61, 0.89). A similar trend was found in men, but it was not statistically significant. Conclusion: This study of Japanese individuals aged 60 years or older provides important evidence that a higher salivary testosterone concentration is associated with lower prevalence of MCI and higher cognitive function in women.