Objective:
Previous studies on the relative risk (RR) of smoking to acute myocardial infarction (AMI) on a province level in China are lack. The aim of this study is to describe the effect of smoking on the incidence of AMI in Tianjin, China during 2010 to 2013.

Methods:
The AMI cases with smoking status were derived from the Tianjin Chronic Disease Incidence Surveillance System. The smoking rates for Tianjin general population by gender and age groups were from the adult tobacco survey in 14 cities from 2013 to 2014, which were used to estimate the corresponding smoking numbers for non-AMI cases from 2010-2013. Average relative risk (RR) for 2010-2013 and 95% confidence intervals (95% CI) of the effect of smoking on the incidence of AMI were calculated. Since AMI mainly occurs after age 40, this paper restricted the population of 40 years old and above.

Results:
From 2010-2013, the average incidence of AMI was 194/100000 for male and 121/100000 for female, respectively, increased with age. The incidence of AMI was higher in men than women at all ages. The average number of smokers in three years was 1,007,043, with men 815,956 and women 191,087 in Tianjin. The RR value of smoking for AMI was 2.44 (95%CI: 2.39, 2.50), 1.72 (95%CI: 1.67, 1.78) and 4.74 (95%CI: 4.56, 4.93) for total, male and female, respectively. RR value decreased with age increasing. RR was about 3 at the age of 45 to 64, then decreased to 2 for people aged 65 and above. The highest RR for male was 3 between 40 and 44 years, and for female was 8 at the age of 40-44 and 60-69 groups.

Conclusions:
The total RR is about 2.44. RR for female is higher than for male. Using the general population to calculate smoking numbers, RR value may be under estimated.