Importance of cognitive assessment as part of the “<scp>K</scp>ihon <scp>C</scp>hecklist” developed by the <scp>J</scp>apanese <scp>M</scp>inistry of <scp>H</scp>ealth, <scp>L</scp>abor and <scp>W</scp>elfare for prediction of frailty at a 2‐year follow up