In adddition to the risk factors listed here (and there are many more), the following research also indicates another risk factor of hardening of arteries through accelerated calcification.

Saremi A, Bahn G, Reaven PD; for the VADT Investigators. Progression of Vascular calcification Is Increased With Statin Use in the Veterans Affairs diabetes Trial (VADT). 1. diabetes Care. 2012 Aug 8. [Epub ahead of print]

OBJECTIVE: To determine the effect of statin use on progression of vascular calcification in type 2 diabetes (T2DM). RESEARCH DESIGN AND METHODS: Progression of coronary artery calcification (CAC) and abdominal aortic artery calcification (AAC) was assessed according to the frequency of statin use in 197 participants with T2DM. RESULTS: After adjustment for baseline CAC and other confounders, progression of CAC was significantly higher in more frequent statin users than in less frequent users (mean - SE, 8.2 - 0.5 mm(3) vs. 4.2 - 1.1 mm(3); P < 0.01). AAC progression was in general not significantly increased with more frequent statin use; in a subgroup of participants initially not receiving statins, however, progression of both CAC and AAC was significantly increased in frequent statin users. CONCLUSION: More frequent statin use is associated with accelerated coronary artery calcification in T2DM patients with advanced atherosclerosis.