Meaning of query age in pg_stat_activity

Hi,

I'm using the following to detect long running queries in a webapp that is
high on cpu:

SELECT pid, age(clock_timestamp(),query_start) as age, usename, query,
state from pg_stat_activity order by age;

When the cpu is 100% and the app slowing down, i can see that some queries
have a long age.
Running the same queries in psql is very fast, however. The db itself is
low on cpu.

Is the age value as i calculate it representing the time spent by the
database to execute the query or does it also include the time to read the
result ? In other words, if the client is starving on cpu, will i see
higher values of age ?

Regards,
Jan