Table 2 Multivariable regression models assessing factors influencing health care utilisation patterns among the fatigue symptom patients, as measured over a one year follow-up period

Characteristic	Outcome variable
	Number of subsequent visits		Number of referrals		Number of investigations
	IRR (95% CI)	p-value	IRR (95% CI)	p-value	IRR (95% CI)	p-value
Age	^*	^*	^*	^*	^*	^*
Female^†	1.12 (0.87–1.44)	0.398	0.41 (0.25–0.67)	<0.001	^*	^*
Previous and co-occurring chronic morbidity^‡	1.01 (1.00–1.03)	0.182	1.01 (0.99–1.03)	0.327	1.01 (0.97–1.04)	0.964
Previous and co-occurring psychosocial morbidity^§	1.01 (0.98–1.03)	0.656	1.02 (0.97–1.06)	0.484	1.04 (0.98–1.09)	0.197
Previous and co-occurring non-chronic, non-psychosocial morbidity^¶	1.00 (0.98–1.01)	0.739	1.05 (1.02–1.07)	<0.001	^*	^*
Previous care-seeking frequency^§§	1.04 (1.03–1.06)	<0.001	0.96 (0.93–0.98)	0.002	0.96 (0.95–0.99)	0.006

Note: IRR = incidence rate ratio, CI = confidence interval.
↵* Variable was not included in the final regression model, as there was no statistically significant relationship with the outcome variable in the bivariate analyses (p > 0.2).
↵† Male fatigue symptom patients designated as the reference group.
↵‡ IRR of a one-point increase in number of previous and co-occurring chronic morbidities.
↵§ IRR of a one-point increase in number of previous and co-occurring psychosocial morbidities.
↵¶ IRR of a one-point increase in number of previous and co-occurring non-chronic, non-psychosocial morbidities.
↵§§ IRR of a one-point increase in the number of in-office visits in preceding year.