Given that cigarette smoking is considered as a risk factor of AD, induced IR and promoted Aβ aggregation have been reported already, and our results showed lower lactate and IGF1 levels and higher insulin and Aβ42 levels in CSF of active smokers, which suggested the association of cigarette smoking with low levels of brain energy metabolism and insulin sensitivity and the at‐risk biomarker of AD. The gene discussed is IGF1; the disease is Alzheimer disease.