Objective To understand the incidence of carotid atherosclerosis (CAS) and the association of CAS with stroke incidence in an occupational population of the Jinchang Cohort, and to provide an evidence for the prevention and treatment of CAS and stroke.

Methods The analysis included 6 262 employees of a nonferrous metal company who participated in the Jinchang Cohort Study and had complete information from the baseline examination, including carotid color Doppler ultrasound, from June 2011 to December 2013 and two rounds of follow-up in 2015 and 2017. The cumulative incidence rates of CAS, carotid intima-media thickening, carotid atherosclerotic plaque, and stroke were calculated among the employees during the follow-up period. A multivariate unconditional logistic regression model was used to analyze the factors associated with CAS, carotid intima-media thickening, and carotid atherosclerotic plaque. A multivariate Cox proportional hazards regression model was used to analyze the risk of stroke incidence and its influencing factors in individuals with CAS, carotid intima-media thickening, and carotid atherosclerotic plaque.

Results During the initial follow-up of a mean of 1.71 ± 0.55 years (ranging from 0.08 to 3.75 years), a total of 1 147 cases of CAS, 287 cases of carotid intima-media thickening, and 860 cases of carotid atherosclerotic plaque were observed, with cumulative incidence rates of 18.32%, 4.58%, and 13.73%, respectively. The results of multivariate unconditional logistic regression analysis showed that age ≥ 45 years, smoking, hypertension, diabetes, abnormal total cholesterol (TC), working as a cadre or technical personnel, and internal staff were risk factors for CAS in the occupational population; whereas education level of college or above was a protective factor; age ≥ 45 years, working as a cadre or technical personnel, smoking, having high-sugar diet, and hypertension were risk factors for carotid intima-media thickening, whereas female gender was a protective factor; females, age ≥ 45 years, working as internal staff, hypertension, diabetes, and abnormal TC were risk factors for carotid atherosclerotic plaque, whereas college education or higher was a protective factor. At the second follow-up of a mean of 2.67 ± 0.55 years (ranging from 0.06 to 4.37 years), a total of 240 stroke cases were identified, with a cumulative incidence of 3.83%. The numbers of stroke cases in subjects with CAS, carotid intima-media thickening, and carotid atherosclerotic plaque were 104, 19, and 85, with cumulative stroke incidences of 9.07%, 6.62%, and 9.88%, respectively. The results of the multivariate Cox proportional hazards regression model analysis showed that after adjusting for gender, age, education level, occupation, smoking, alcohol consumption, physical activity, high-salt diet, high-fat diet, high-sugar diet, hypertension, diabetes, hyperuricemia, body mass index (BMI), abnormal TC, abnormal triglycerides (TG), abnormal high-density lipoprotein cholesterol (HDL-C), abnormal low-density lipoprotein cholesterol (LDL-C), and reduced glomerular filtration rate, the risk of stroke was significantly increased in the individuals with CAS (hazard ratio HR = 1.421, 95% confidence interval 95%CI: 1.030 – 1.961) compared with those without CAS. The results also showed that, age ≥ 45 years, high-salt diet, and overweight were risk factors for stroke incidence in the individuals with CAS; females and hyperuricemia were risk factors for stroke incidence in individuals with carotid intima-media thickening; and high school or technical secondary school education, high-salt diet, and overweight were risk factors for stroke incidence in individuals with carotid atherosclerotic plaque.

Conclusion The cumulative incidence of both CAS and stroke was high during follow-up in the occupational population of the Jinchang Cohort Study and in the occupational population, the individuals with CAS had a higher risk of stroke, and older age, high-salt diet, and overweight were the main risk factors for stroke in the individuals with CAS.