Cardiohealth station

At the resurvey, ultrasound examination was performed using a Panasonic CardioHealth Station in each of the four segments of the carotid arteries on both sides, including the distal common carotid artery (CCA), carotid bifurcation, proximal internal carotid artery, and proximal external carotid artery. The cIMT was measured only in the distal 1 cm of the CCA just before the bifurcation at 150° and 120° for right CCA and at 210° and 240° for left CCA. Mean cIMT was estimated as the mean of these four measurements. All four segments were screened for the presence of plaques. Carotid plaque was defined as any focal thickening or protrusion from the wall into the lumen with cIMT >1.5 mm (32 (link)). Carotid plaque burden was derived by standardizing the plaque number and maximum size and estimating the average, then multiplying the average value by the standard deviation (SD) of the maximum plaque thickness to provide a measure of plaque burden recorded in mm (33 (link), 34 (link)). Details of carotid artery ultrasonography measurements were described previously (33 (link)) and in Supplementary methods.

Ultrasound images of the common carotid arteries were obtained in short and long axes from low in the neck up to the jaw, at least to the level of the carotid bifurcation using a CardioHealth Station (Panasonic Healthcare Corporation of North America, Newark, NJ, 19 USA), with a 9MHz linear array transducer. CIMT was measured at two angles for each carotid (150^o /120^o right and 210^o/240^o left) and the mean, maximum and minimum CIMT tracking for each carotid was recorded [12 (link)].

Vascular structure was determined by measuring intima-media thickness of the common carotid artery (cIMT) as previously described [17 (link),18 (link)]. In brief, all measurements were performed using the Cardiohealth Station of Panasonic (Yokohama, Japan), a semiautomated ultrasound system. With B-Mode, 4 measurements of cIMT at the far wall of the common carotid artery, 1 cm distal to the bulb, were recorded, and a mean value was calculated and used for all following analyses (Figure 1). The central frequency of the linear-array transducer was 8.9 MHz. Short-term and 1-week inter- and intra-operator cIMT measurement variability of the Cardiohealth Station is acceptable in healthy, young to middle-aged adults [19 (link)].

During the 16-year medical examination, trained medical technicians used a portable ultrasound system, the Panasonic CardioHealth Station (Panasonic Healthcare), to automatically measure bilaterally the IMT in the distal common carotid artery proximal to the bifurcation at six standard angles (left: 210°, 240° and 270°; right: 90°, 120° and 150°). The CardioHealth Station minimizes measurement error by automatically identifying the relevant region and measures CIMT over a standard length of 10 mm in the end-diastolic phase of a participant’s heartbeat. The mean CIMT measurement utilized as the primary outcome in this analysis was determined by averaging the six IMT measurement angles. If less than six measurements were available, the mean CIMT was computed with the available measurements if there were at least 3 IMT measurements available.