Introduction and Purpose

It is well established that atherosclerotic diseases occurring in intracranial and extracranial carotid arteries are associated with ischemic cerebrovascular events. Early identification of cerebrovascular atherosclerosis in asymptomatic individuals is important for stroke prevention. Magnetic resonance imaging vessel wall imaging, particularly three-dimensional imaging techniques, is the best non-invasive tool for plaque characterization. Apparently, MR imaging is not a cost-effective screening tool for atherosclerosis. Therefore, it is warranted to find a surrogate risk factor for cerebrovascular atherosclerosis in asymptomatic subjects. Previous studies have shown that age is associated with carotid and intracranial artery atherosclerosis ^[1-3]. However, the relationship between age and subclinical cerebrovascular plaques in Chinese community-based population is unknown. The purpose of this study is to investigate the association between age and subclinical cerebrovascular atherosclerosis in community-based adults using MR vessel wall imaging.

Methods

Study sample: The subjects were recruited from a community study of CAMERA-TSINGHUA in which cerebrovascular disease risk was investigated in community-based population. All subjects underwent MR vessel wall imaging for both intracranial and extracranial carotid arteries. The study protocol was approved by institutional review board and written consent form was obtained by each subject. MR imaging: The T1-VISTA and 3D-MERGE imaging sequences were acquired for intracranial and extracranial carotid arteries respectively on a 3.0T MR scanner (Achieva TX, Philips Healthcare) with a custom-designed 36-channel neurovascular coil and the following parameters: T1-VISTA: turbo spin echo; repeat time (TR)/echo time (TE) 700/21 ms, flip angle 90°, field of view (FOV) 20x20x4.5 cm³, and spatial resolution 0.6x0.6x0.6 mm³; and 3D MERGE: fast field echo, TR/TE 9/4.2 ms, flip angle 6°, FOV 25x16x4 cm³, and spatial resolution 0.8x0.8x0.8 mm³. Image analysis: MR images were reviewed by two radiologists with >5 years’ experience in cardiovascular imaging using a custom-designed software with consensus. Presence/absence of atherosclerotic plaque which is defined as eccentric wall thickening in the vessel wall was determined in intracranial and extracranial carotid arteries. Statistical analysis: The subjects were divided into 6 groups by age: <40 years, 40-49 years, 50-59 years, 60-69 years, 70-79 years, and ≥ 80 years. Prevalence of atherosclerotic plaque in intracranial artery, extracranial carotid artery, and both intra- and extracranial carotid arteries was calculated in each age group. The relationship between age and presence of cerebrovascular plaque was assessed to calculate odds ratio (OR) and corresponding 95% confidence interval (CI) using logistic regression model.

Results

Of 476 recruited asymptomatic subjects (mean age, 61.4±13.9 years; 195 males), 14 (2.9%), 206 (43.3%), and 57 (12%) had subclinical atherosclerotic plaque in intracranial artery only, extracranial carotid artery only, and both intracranial and extracranial carotid arteries, respectively. An increasing trend was found in the prevalence of plaques in each cerebrovascular bed with age (Fig. 1). Univariate logistic regression showed that age was significantly associated with presence of atherosclerotic plaque in intracranial artery only (OR=1.77, 95% CI 1.34-2.35, p<0.0001), extracranial carotid artery only (OR=1.42, 95% CI 1.31-1.55, p<0.0001), and both intracranial and extracranial arteries (OR=1.79, 95% CI 1.53-2.10, p<0.0001) with increment of 5 years. After adjusted for confounding factors of gender, body mass index, hypertension, smoke, diabetes, and levels of lipoproteins, above associations remained statistically significant (all p<0.001, Table 1). Fig. 2 represents example for an old subject with subclinical atherosclerotic plaques in both intracranial and extractranial carotid arteries.

Discussion and Conclusion

In the present study, the prevalence of cerebrovascular atherosclerotic plaques was found to be increasing with age. The association between age and cerebrovascular atherosclerosis suggests that age was an independent indicator for subclinical cerebrovascular atherosclerosis. Previous studies have shown that the arterial compliance ^[4] and function of endothealial cells ^[5] will decline with age which may lead to arteries becoming more susceptible to developing atheroma. In addition, we found that 12.8% of subjects <40 years old had carotid plaque but none had intracranial artery plaques, indicating that atherosclerotic disease may initiate earlier in carotid arteries than that in intracranial arteries.

Acknowledgements

This study is supported by grants of Beijing Municipal Science and Technology Commission (D131100002313002) and Beijing Municipal Commission of Health and Family Planning (2016-1-2041).