Smoking may be the biggest contributor to cognitive decline and whether or not older people will develop dementia, according to new research. A study conducted by researchers at University College London analyzed lifestyle combinations using data from 32,000 adults. The researchers used four key lifestyle factors: smoking, alcohol consumption, physical activity, and social contact. Over a 10-year period, smokers experienced a memory decline of 0.17 deviations more than non-smokers. Smokers’ verbal fluency scores also decline by 0.16 standard deviations more than non-smokers. Smokers who exhibited heavy alcohol consumption, low exercise rates, and limited social contact experienced the most rapid cognitive decline.