Is there a sex difference in adult salivary clearance of caffeine (1,3,7-trimethylpurine-2,6-dione)?

BACKGROUND

The salivary caffeine clearance is a non-invasive, safe, saliva-based method for assessing hepatic function and diagnosing chronic liver disease. The elimination of caffeine from the body follows first-order kinetics and principally involves catabolism by hepatic CYP1A2, with a half-life usually between three and 7 h. It is known that this process is affected by age and smoking tobacco. It has been suggested that sex might also be important, but there is scant evidence for this. The aim of this study was to assess whether there is a sex difference in salivary caffeine clearance in adults.

METHODS

A cohort of 213 adults was studied. They were all non-smokers and none suffered from chronic liver disease. They consisted of 67 men (mean age 40.0 years) and 146 women (mean age 44.7 years). Following a period of dietary caffeine abstinence lasting at least 24 h, each subject ingested a single oral dose in the morning of caffeine, at a dose of 3 mg per kg body mass. Salivary samples were collected at 2 h and 14 h post-caffeine ingestion and were spectrophotometrically assayed for their caffeine concentrations.

RESULTS

The two groups were matched for age. The mean (standard error) salivary caffeine clearance in the male subjects was 1.51 (0.10) mL min kg, while that in the female subjects was 1.60 (0.07) mL min kg ( = 0.495).

CONCLUSION

This relatively large study provides no evidence of a sex difference in salivary caffeine clearance.