Medical researchers, seeking insight, sometimes try to make simple sense of complex, difficult conglomerations of things that may or may not have effects on each other and on many other things. Sometimes coffee is involved, as is the case here:
“Indoor Air Pollution, Nighttime Heart Rate Variability and Coffee Consumption among Convenient Store Workers,” Kai-Jen Chuang, Hsiao-Chi Chuang, Lian-Yu Lin, PLoS One, 2013 Aug 15;8(8):e63320. The authors, at Taipei Medical University, report:
“The aim of this study was to investigate the association of HRV [heart rate variability] indices with indoor air pollution, working time and coffee consumption…. We recruited 60 young healthy convenient store workers to monitor indoor PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 µm) exposures, coffee consumption (yes vs. no) and HRV indices during daytime (0700-1500 hours) and nighttime (2300-0700 hours)….
“CONCLUSIONS: …The effect of indoor PM2.5 on HRV indices may be modified by coffee consumption in young healthy convenient store workers.”
BONUS: Correlation is not causation, or so they say, some of them, sometimes.