Long-Term Effect of Caffeine Intake on Speech and Sound Perception in People with Normal Hearing

Background and Aim: Caffeine intake enhances concentration through affecting brain functions. It also improves attention to the signal which is believed to be associated with increased noise tolerance and improved speech perception. This study aimed to evaluate the long-term effects of caffeine intake on simultaneous speech and sound perception in people with normal hearing. Methods: This double-blind study was conducted on 90 people aged 18-34 years (45 males and 45 females), randomly assigned to two intervention groups (receiving 3 and 5 mg/kg caffeine) and a control group (receiving placebo). The acceptable noise level (ANL) test was conducted before and five hours after intervention. Results: Comparison of ANL scores before and after intervention showed a significant difference in the 3 mg/kg caffeine group (p=0.002), but not in the placebo (p=0.497) and 5 mg/kg caffeine (p=0.146) groups. Between-group analysis showed a significant difference between the placebo and 3 mg/kg caffeine groups in the ANL five hours after (p=0.005), while the difference was not significant between the placebo and the 5 mg/kg caffeine groups (p=0.139). Moreover, there was no significant difference in the ANL between the 3 and 5 mg/ kg caffeine groups (p=0.148). Conclusion: Caffeine intake affects noise tolerance, depending on the dose of caffeine. The ANL and speech tolerance improve five hours after consuming 3 mg/kg of caffeine. Keywords: Caffeine; noise perception; normal hearing; acceptable noise level test