How does online backup work?
You can go to Settings > Manage your data to create an online backup or export your sleep data.
With iCloud online backup you can change, restore or upgrade your device without having to worry about losing your sleep data. Your data will be safely stored on your iCloud account and can be restored from there.
Please note that if you delete the app or upgrade to a new phone without backing up your data, your historic sleep data will be lost.