They performed a prospective cohort study – this involves following over time groups of individuals who are alike in many ways but differ by a certain characteristic (for example, female nurses who smoke and those who do not smoke) and compares them for a particular outcome (such as lung cancer).
The researchers performed this study on The Nurses’ Health Study (one of the largest investigations into the risk factors for major chronic diseases in women) and the Health Professionals Follow-Up Study (a study evaluating a series of hypotheses about men’s health relating nutritional factors to the incidence of serious illnesses).
Five lifestyle factors were strongly associated with greater life expectancy: never smoking, body mass index (BMI) of 18.5-24.9, moderate to vigorous physical activity, moderate alcohol intake, and a higher diet quality score.
BMI is a measure of whether you’re a healthy weight for your height.
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