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Letters Every step you take

Authors’ reply to Johnson

BMJ 2019; 366 doi: (Published 30 September 2019) Cite this as: BMJ 2019;366:l5715
  1. Ulf Ekelund, professor1,
  2. I-Min Lee, professor2
  1. 1Department of Sports Medicine, Norwegian School of Sport Sciences, PO Box 4014, Ullevål Stadion, 0806 Oslo, Norway
  2. 2Division of Preventive Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
  1. ulf.ekelund{at}

We agree with Johnson that our sample including eight cohorts might not be representative of the physical activity levels in the four countries they represent.12 But three of the included cohorts—NNPAS (Norway), NHANES (US) and ABC (Sweden)—comprised nationally representative samples with generally …

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