Observational studies have shown that several lifestyle choices and habits, such as eating too much refined sugar or drinking more than one glass of wine a day, may have adverse health effects.1 2 The linked prospective cohort study by Kabrhel and colleagues (doi:10.1136/bmj.d3867) adds inactivity to this list of sins.3 The study followed 69 950 female nurses for an average of 18 years. Those women who were the most inactive, defined by the number of hours of sitting a day (>41 hours a week outside of work), were two to three times more likely to develop otherwise unprovoked venous thromboembolism (VTE), which manifested as pulmonary embolism, than women who spent the least amount of time sitting (<10 hours a week outside of work). The association remained robust after controlling for other risk factors for VTE such as increasing age, body mass index, and concomitant disease, and was not mitigated by periods of physical activity and exercise.

If the findings are valid they may have major public health ramifications. The study also showed that physical inactivity correlated with coronary heart disease (spanning from 1.2% to 5.1% across fifths of physical inactivity) and hypertension (from 18% to 25%). Prolonged periods of physical inactivity could be …