Effects of chronic and acute smoking on AMLRs in older and younger listeners.

Chronic and acute smoking effects on the auditory middle latency response (AMLR) were studied in older (55-81 years) and younger (19-30 years) normal-hearing listeners. Forty healthy participants were selected for one of four groups: older smokers, older nonsmokers, younger smokers, or younger nonsmokers. Biochemical urine analyses confirmed participant categorization as smoker or nonsmoker. Click-evoked AMLRs were acquired once from nonsmokers and twice (chronic condition, acute condition) from smokers. Waveform latency (V, Na, Pa) and relative amplitude (V-Na, Na-Pa) were examined with two independent variables (age, smoking) using MANOVA. Results (n=40) revealed no chronic effect of smoking in the AMLR from smokers compared to nonsmokers. However, in both older and younger smokers (n=20), Na-Pa amplitude was significantly larger in the acute compared to the chronic smoking condition, indicating an acute smoking effect. There was no interaction of smoking and aging. This is a first study describing long-term, chronic and acute smoking effects on AMLRs in older compared to younger listeners. Results suggest that cigarette smoking is an important variable for AMLR research and clinical practice.