The search strategy resulted in the identification of 489 unique publications (Fig. 1). Upon screening of titles and abstracts, and subsequent assessment of full-text records for eligibility, 19 articles reporting costs of DMD were included for synthesis and assessment of risk of bias [16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34]. Summary characteristics of the included publications are presented in Table 1. In total, ten (53%) were retrospective cohort studies, eight (42%) cross-sectional studies, and one (5%) was a modeling study. Identified studies encompassed a total of 6993 patients with DMD, with individual study samples ranging between 27 and 1722 cases. The age of patients ranged between 1 year and 43 years (11 studies did not report minimum and maximum ages [16, 18, 20,21,22,23, 27,28,29,30, 34]).

Fig. 1

PRISMA diagram of the selection process of the included publications

Table 1 Characteristics of included studies reporting costs of DMD3.1 In Which Geographical Settings Have Costs of DMD Been Studied?

Estimates of costs of illness of DMD were found for samples of patients from the following countries: Australia [33], Brazil [30], Bulgaria [18], Denmark [29], Egypt [32], France [18], Germany [18, 20, 26, 31], Hungary [18], Italy [18, 26], Portugal [24], Spain [18], Sweden [18], the UK [18, 26], and the USA [16, 17, 19, 21,22,23, 26,27,28, 34]. In total, two studies (11%) included patients from more than one country [18, 26], and ten studies (53%) represented research of patients from the USA [16, 17, 19, 21,22,23, 26,27,28, 34].

3.2 What Types of Costs Have Been Estimated in Patients with DMD?

In total, 16 (84%) studies estimated the per-patient annual direct medical cost of DMD [18,19,20,21, 23,24,25,26,27,28,29,30,31,32,33,34], 9 (47%) the per-patient annual direct nonmedical cost [18, 24,25,26,27, 30,31,32,33], 7 (37%) the per-patient annual informal care cost [18, 24,25,26, 31,32,33] (in all studies captured as a direct nonmedical cost), 10 (53%) the per-patient annual indirect (productivity) cost (patient and/or caregiver) [18, 24,25,26,27, 29,30,31,32,33], and 10 (53%) the per-patient annual total cost of illness [18, 24,25,26,27, 29,30,31,32,33] (Table 2). Additionally, one study (5%) estimated the per-patient annual personal care/facility cost of DMD [16], two studies (11%) household costs [22, 26], one study (5%) cost of hospitalization [17], and one study (5%) costs of special education [29].

Table 2 Costs of DMD reported by included studies3.3 What are the Known Costs of DMD?3.3.1 Direct Medical Costs of DMD

Estimates of the mean per-patient annual direct medical cost of DMD ranged from $2620 in Hungary (mean patient age: 12 years) [18] to $209,980 in the USA (late nonambulatory patients—mean patient age: 23 years) [21] (Table 2). As illustrated in Table 3, there was some variability across studies concerning included medical resources. Identified estimates of direct medical costs stratified by disease stage (early/late ambulatory/nonambulatory and confined to bed) are shown in Fig. 2. Across included studies, costs were on average 2.00 times higher for the late compared with the early ambulatory stage (range: 0.70–6.24), 1.45 times higher for the early nonambulatory compared with the late ambulatory stage (range: 1.06–1.97), and 1.48 times higher for the late nonambulatory compared with the early nonambulatory stage (range: 0.78–2.89). On average, direct medical costs accounted for 27% of total costs (range: 4–81%). Additionally, Klimchak et al. [23] reported estimates of the median direct medical cost of DMD in the USA (Table 2).

Table 3 Resources included in identified estimates of the direct medical cost of DMDFig. 2

Mean per-patient annual direct medical cost of Duchenne muscular dystrophy (DMD). Costs were converted using country-specific consumer price index data from OECD, the World Bank, and US Bureau of Labor Statistics, as well as purchasing power parities data from OECD, and rounded to the nearest ten. EG, Egypt; DE, Germany; IT, Italy; UK, United Kingdom; US, United States

3.3.2 Direct Nonmedical Costs of DMD

The mean per-patient annual direct nonmedical cost of DMD was estimated at between $5670 in Brazil (total sample) [30] and $103,800 in Australia (patient age: 25–34 years) [