Table 1.

Summary of the relationship between multimorbidity, costs, and utilisation^a

Utilisation/cost type	MM specification		Magnitude (95% CI)	Parameter estimate type	Reference
Primary care visits (n = 3)
	Number of QOF LTCs		0.37 (0.36 to 0.38)	Marginal effect	28
	MM vs not		2.56 (2.48 to 2.64)	Odds ratio	3
Dental visits (n = 1)
	MM vs not		1.23 (1.08 to 1.38)	Odds ratio	36
A&E visits (n = 2)
	HADS score of 8 or more vs lower		1.58 (1.04 to 2.41)	Odds ratio	35
	1 QOF LTC vs none		1.12 (1.10 to 1.13)	Odds ratio	24
	2 QOF LTC vs none		1.28 (1.25 to 1.31)	Odds ratio	24
	3 QOF LTC vs none		1.65 (1.59 to 1.71)	Odds ratio	24
	≥4 QOF LTC vs none		2.55 (2.44 to 2.66)	Odds ratio	24
Hospitalisations (n = 4)
All	1 LTC vs none		1.77 (1.59 to 1.98)	Odds ratio	33
	2 LTC vs none		2.41 (2.12 to 2.72)	Odds ratio	33
	3 LTC vs none		3.53 (3.06 to 4.07)	Odds ratio	33
	≥4 QOF LTC vs none		4.33 (3.63 to 5.17)	Odds ratio	33
	MM vs not		2.58 (2.48 to 2.69)	Yearly rate ratio	3
Unplanned all	1 PC vs none		1.70 (1.59 to 1.82)	Odds ratio	27
	2 PC vs none		2.69 (2.50 to 2.89)	Odds ratio	27
	3 PC vs none		3.47 (3.21 to 3.76)	Odds ratio	27
	≥4 PC vs none		5.87 (5.45 to 6.32)	Odds ratio	27
Unplanned potentially preventable	1 PC vs none		2.50 (2.07 to 3.03)	Odds ratio	27
	2 PC vs none		4.93 (4.06 to 5.99)	Odds ratio	27
	3 PC vs none		6.82 (5.55 to 8.37)	Odds ratio	27
	≥4 PC vs none		14.38 (11.87 to 17.43)	Odds ratio	27
Prolonged length of stay	MM vs not (90+ population)		0.61 (0.32 to 1.13)	Risk ratio	23
Total costs (n = 3)
	1–3 LTC vs none		1.62 (1.28 to 2.03)	Mean ratio	31
	4–6 LTC vs none		2.53 (2.01 to 3.19)	Mean ratio	31
	7–9 LTC vs none		3.82 (3.01 to 4.85)	Mean ratio	31
	1 LTC vs none		1.99 (1.95 to 2.03)	Mean ratio	26
	2 LTC vs none		2.53 (2.46 to 2.58)	Mean ratio	26
	3 LTC vs none		2.86 (2.72 to 3.03)	Mean ratio	26
Care transition costs (n = 1)	Comorbidity pairs vs index LTC		P<0.001	Increasing trend in association	34
Primary care costs (n = 2)	Costs of 1 patient with 2		Increasing or decreasing costs when co-occurring	Estimated prevalence- adjusted cost	13
	LTC vs 2 separate
	patients with each LTC
Hospital costs (n = 1)	Individual LTC		P<0.01 for 90% of the estimated coefficients	Estimated coefficient	25
	Time to death as a proxy for morbidity

^aThe number of articles is indicated in parentheses next to the cost or utilisation type (see Supplementary Appendix S3 for the complete 17 study references). Mean ratios can be obtained by exponentiating the parameter estimates from a generalised linear model with the log-link; they have an interpretation similar to an odds ratio. For example, individuals with 7–9 conditions have 3.82 times the mean expected total costs of individuals without comorbidities. A&E = accident and emergency. CI = confidence interval. HADS = Hospital Anxiety and Depression Scale. LTC = long-term condition. MM = multimorbidity. PC = physical condition. QOF = Quality and Outcomes Framework. Prolonged length of stay is defined as 7 days in the hospital. Care transitions are defined as healthcare changes from general practice to emergency department or hospital care.