A symptom diary is only useful if two things are true: you keep filling it in, and you can read it back later. Most diaries fail the first test by asking too much, and the second by recording prose that nobody can scan.
What an AS diary is for
Three things, in order of how often they come up. First, answering "how have you been?" at a review with something better than recall. Second, noticing what tends to sit alongside worse stretches in your own history — poor sleep, a heavy week, a missed dose. Third, keeping a truthful record of flares: when they started, how long they lasted, what you did.
It is not for finding the cause of your AS. A diary can show that two things tended to occur together in your record; it cannot show that one caused the other. See how to track pain patterns.
The structure
Numbers first, words second. Numbers can be charted and compared; words cannot. A workable daily entry looks like this:
| Field | Format | Example |
|---|---|---|
| Morning stiffness | Duration band | 30–60 min |
| Spinal pain | 0–10 | 4 |
| Other joints | 0–10 + where | 2, left knee |
| Fatigue | 0–10 | 6 |
| Sleep | Hours + disturbed? | 6 h, woke twice |
| Flare? | Yes / no, start date if new | No |
| Medication | As taken, changes only | Missed evening dose |
| Activity | One line | Mobility 20 min, scaled down |
| Note | One line, only if something happened | Long drive yesterday |
Record stiffness and pain separately. They behave differently and a clinician will ask about them differently. Fatigue also gets its own line: it has its own BASDAI question because research at Bath identified it as a major component of AS, and the index was developed with input from people with AS (Garrett et al., 1994).
Paper or app
Paper is fast and private, and the printable AS symptom diary template is laid out for it. Its weakness is the read-back: a month of pages is hard to scan for a trend, and impossible to chart.
An app trades a little friction at entry for a great deal at review. The signals become charts, flares become shaded ranges, and a period can be summarised for an appointment. HAVYT’s AS Mode is built around exactly this diary structure, with training, medication and connected health data recorded alongside rather than in a separate place.
Reading it back
Once a month, or before an appointment, look at the whole record rather than the last few days. Ask three questions of it:
- What is the direction? Are stiffness and pain drifting up, down or flat over the period?
- Where are the worst stretches, and how long did they last?
- What was different in the days before those stretches — sleep, training, medication, illness, travel?
The third question is the one to be careful with. An association in your own record is worth raising with your rheumatology team; it is not a finding, and it should not change your treatment on its own.