As we age, the immune system gradually becomes impaired. One aspect of this impairment is chronic inflammation in the elderly, which means that the immune system is constantly active and sends out inflammatory substances. Such chronic inflammation is associated with multiple age-related diseases including arthritis and Alzheimer’s disease, and impaired immune responses to infection. One of the questions in ageing research is whether chronic inflammation is a cause of aging, or a consequence of the aging process itself? Scientists have found evidence suggesting that increased inflammation causes the aging process to speed up, and that there is a fine balance between maintaining immune system function and longevity.