LONDON (Reuters) -British American Tobacco said it would take a hit of around $31.5 billion as it writes down the value of some U.S. cigarette brands, acknowledging on Wednesday that its traditional market has no long term future. BAT's move comes as ever stricter regulation and growing awareness of health risks squeeze tobacco companies' traditional business, driving declines in cigarette volumes in some markets. The maker of Lucky Strike and Dunhill cigarettes also pointed to economic challenges in the U.S., where some inflation-weary consumers are downgrading to cheaper brands, and the rise of illicit disposable vapes putting pressure on its U.S. cigarette division.