Apple Watch heart rate variability data found to be inconsistent

Heart rate variability (HRV) data collected by the Apple Watch was found to be inconsistent, prompting questions about the system's reliability.

Harvard biostatistics researcher JP Onnela discovered that it is not possible to use Apple Watches for research into heart rate variability after finding the data collected was inconsistent. 

According to Onnela, updates to Apple Watch algorithms mean 'the data from the time period can change without warning'. 

'These algorithms are what we would call black boxes — they’re not transparent. So it’s impossible to know what’s in them' he argued.

The finding highlighted the need for careful interpretation of Apple Watch HRV data.