Objective: Whereas caffeine has been demonstrated to impact substantially on the metabolic response to exercise in healthy young subjects, this issue remains to be addressed in healthy elderly subjects.
Design and patients: The metabolic response to caffeine ingestion (6 mg/kg) and exercise in healthy elderly citizens at 70 years was examined in a randomized, double-blind, placebo-controlled, cross-over study. We included 30 subjects attending for driver license renewal at their general practitioner. Participants abstained from caffeinated drinks and food for 48 h and were randomized to receive placebo-caffeine or caffeine-placebo with 1 week between sessions.
Measurements: A cycling endurance test at 65% of the expected maximal heart rate was performed 1 h after intervention. Blood samples were taken before intervention, before cycling, after 5 min of cycling, and at exhaustion. Analysis was by intention-to-treat and P < 0.05 was regarded as significant.
Results: Caffeine significantly increased the concentration of plasma epinephrine (by 42%, 39%, and 49%), serum-free fatty acids (by 53%, 44%, and 50%), and plasma lactate (by 46%, 36%, and 48%), and insulin resistance (homeostasis model assessment-IR) (by 21%, 26%, and 23%) during rest, after 5 min of cycling, and at exhaustion. At exhaustion, the concentration plasma norepinephrine was elevated by 29%. A decrease was seen with caffeine treatment in blood potassium after 5 min of cycling and at exhaustion (by 3% and 2%, respectively).
Conclusions: Caffeine treatment increased epinephrine, fatty acids, lactate and norepinephrine at different times during test session and led to insulin-resistance. Hence, caffeine ingestion elicits a similar metabolic response in elderly participants at 70 years old to that seen in younger subjects.