Chronic pain affects more than 8.5 million people in the UK and costs the economy 18 billion pounds a year in lost work days; while an estimated 30%, or up to 70 million people, also suffer in the US, where it's said to be the most costly health problem. Yet, according to one study, two out of three people say that their medication is not always adequate, while 96% of GPs believe there is significant room for improving treatment. Another survey found that a half to two-thirds of people with chronic pain are less able or unable to exercise, enjoy normal sleep, perform household chores, attend social activities, drive a car, or walk; while a quarter find that relationships with family and friends are strained or broken. Neck pain, back pain, arthritis, allergies and depression are listed as the top five chronic health problems.