this update statement takes 10 to 20 seconds to run. anyway to tune up the statement?

update ea
set ea.Next_Activity_Date_New = rn.date_
from employee_accounts ea
inner join (select min(appt_date) as date_,company from rn_appointments
where appt_date > convert(varchar(20), getdate(),1) and (activity_complete is null or activity_complete = 0)
group by company) as rn
on rn.company = ea.company_id
where (ea.delete_flag is null or ea.delete_flag = 0) and ea.employee_id = @employee_id