Inflammation has long been regarded as a tissue repair mechanism activated by the body in response to infection or tissue injury. In recent years, chronic inflammation has been implicated as a proinflammatory factor not only in various diseases, such as cancer, atherosclerosis, obesity, and Alzheimer’s disease, which increase with age, but also in the aging process itself. What mechanisms cause the inflammatory response that normally dissipates, persists, and becomes chronic? Elucidating the factors that cause chronic inflammation and the mechanisms that induce it will provide insights into the prevention and control of various age-related diseases. In this review, we focus on proteoglycans as factors that cause chronic inflammation and discuss proteoglycans as DAMPs that cause inflammation.