A hazard ratio is the measure of how often an event occurs in one group compared to a control group over time. A hazard ratio of one (=1) indicates no difference in survival between the two groups, while a hazard ratio greater than one (>1) indicates that the treatment group had a shorter survival rate compared to the control group. 

University of Michigan - Ann Arbor

A Swedish study of 233,879 males and 1,413,849 females without history of psychosis found that there was a 3.45 hazard ratio for first-onset schizophrenia in heavily smoking females and a 3.80 hazard ratio for heavily smoking males, compared to a 2.21 hazard ratio for lightly smoking females and 2.15 hazard ratio for lightly smoking males. 

Swedish Population Study


NCI Dictionary of Cancer terms. National Cancer Institute. (n.d.). https://www.cancer.gov/publications/dictionaries/cancer-terms/def/hazard-ratio 

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