seems not, you may have to try something like counting the results from the aiClientTable, such as aiClientMACAddress, e.g.
root@kali:/home/mibs/6.4.4.6# snmpwalk -v2c -c secret123 -mALL -M. -O0X 192.168.1.123 aiClientMACAddress 2>&1 | grep STRING | wc -l
2
root@kali:/home/mibs/6.4.4.6#
root@kali:/home/mibs/6.4.4.6# snmpwalk -v2c -c secret123 -mALL -M. -O0X 192.168.1.123 aiClientMACAddress 2>&1 | grep STRING
AI-AP-MIB::aiClientMACAddress[STRING: 9a:fb:e0:07:a2:12] = STRING: 9a:fb:e0:07:a2:12
AI-AP-MIB::aiClientMACAddress[STRING: f4:5c:81:97:e2:61] = STRING: f4:5c:81:97:e2:61
root@bt:/home/mibs/6.4.4.6#
however, associated clients which dont have an IP dont show up in the above results (found that by accident when capturing the above), just a point to note.