Response to Farrokhi et al.’s statistical comments on ‘no seasonal variation in physical activity of Han Chinese living in Beijing’
© The Author(s). 2017
Received: 17 October 2017
Accepted: 20 October 2017
Published: 3 November 2017
We note from these revised analyses that for the body composition measurements we made the main effect was that the individuals were significantly fatter and heavier later in the study (November) compared with earlier (January). Because our measurements spanned only a single year we cannot distinguish whether this was a seasonal effect, or because the individuals were all getting older as the study progressed. In contrast fat-free mass did not progressively increase but was higher both at the start and end, but lower in the summer period in the middle. This may be a true seasonal effect, but additional years of study would be required to confirm that. Previous studies have shown adult individuals in the USA gain around 0.5 kg each year as they age  and the magnitude of this effect is consistent with the change we observed in weight and fatness. We emphasise that the other statistical analyses in the original paper concerning physical activity levels did account for repeated measurements, and these analyses, and the conclusions drawn from them, are unaffected by this error.
GW and JRS reanalyzed the data and co-wrote the response. Both authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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