What causes blood flow to hands and arms to be restricted?

Blood flow to the hands and arms can be restricted due to various factors, including vascular conditions like atherosclerosis, where arteries narrow due to plaque buildup. Additionally, external compression from tight clothing or repetitive movements can impede circulation. Other causes may include nerve compression, such as carpal tunnel syndrome, and systemic conditions like Diabetes or Raynaud's phenomenon, which affects blood vessel response to cold or stress.