Table 2 Overview of variables for retrospective observational cohort study (phase 1) and interrupted time series (phase 3)

Patient characteristics

Age

In years at time of registration ICPC code for vestibular symptoms

Sex

Male or female

Diagnosed vestibular disorder

According to ICPC code (see Table 1)

Comorbidity

According to the following ICPC codes: K86 (Hypertension uncomplicated), K87 (Hypertension complicated), K83 (Heart valve disease), K84 (Heart disease other), K75 (Acute myocardial infarction), K76 (Ischaemic heart disease without angina), T90 (Diabetes), K89 (Transient cerebral ischaemia), K90 (Stroke/cerebrovascular accident), P74 (Anxiety disorder/anxiety state), P76 (Depressive disorder), A49.02 (Polypharmacy)

General practice characteristics

Registered patients

Total number of patients registered at practice per year and total number of adult patients (aged 18 years and over) registered at practice per year

Employed general practitioners

Total number of general practitioners per year with patients registered to their name

Degree of urbanisation

Based on 4-digit postal code: not/hardly urbanised (< 1.000 surrounding addresses), moderately urbanised (1.000–1.500 surrounding addresses), strongly urbanised (1.500–2.500 surrounding addresses), and extremely urbanised (> 2.500 surrounding addresses)

Other

Date of registration ICPC code for vestibular symptoms

-

Date of registration and deregistration at general practice

-

Referral for vestibular rehabilitation^a

As described in electronic patient record

Prescription for anti-vertigo drug

According to the ATC code (see Table 1)

Date of prescription

-

Referrals to physiotherapist, ENT specialist, neurologist, and/or geriatrician^a

As described in electronic patient record

GP consultations

Total number of GP consultations (all types of consultations, including telephone consultations and home visits) per patient per year for vestibular symptoms