In fact, plasma metabolomic analysis showed that PD patients (70 sPD, 118 LRRK2-PD) had lower levels of plasma caffeine concentration compared with healthy individuals (65 HC, 115 LRRK2-NMC), more so in LRRK2-positive (by 76%) compared with LRRK2-negative carriers (by 31%), with significant interaction between LRRK2 and PD status [49•]. The gene discussed is LRRK2; the disease is Parkinson disease.