Cost of Depression Among Adults in Japan

Cost of Depression Among Adults in Japan

Yasuyuki Okumura, PhD, and Teruhiko Higuchi, MD, PhD

Objective: The aim of this study was to estimate the annual national cost of major depressive disorder among adults 20 years and older in Japan in 2008.

Method: The analysis used was a top-down costing approach based on national health statistics. From the societal perspective, the costs examined were direct medical costs, depression-related suicide costs, and workplace costs for all members of society. Direct medical costs included both inpatient and outpatient medical costs, while workplace costs included both absenteeism and presenteeism costs. The authors performed 1-way sensitivity analyses to examine the extent to which results were affected by the choice of parameters used in the cost calculation. All costs were expressed in 2008 US dollar terms.

Results: The economic burden of depression in Japan was approximately $11 billion, with $1,570 million relating to direct medical costs, $2,542 million to depression-related suicide costs, and $6,912 million to workplace costs. Compared to previously published studies, this study adopted conservative key assumptions; this may have resulted in a conservative estimate of the annual national cost of depression.

Conclusions: Depression imposes a substantial economic burden on Japanese society, which highlights the urgent need for policymakers to allocate resources toward implementing strategies that prevent and manage depression in the Japanese population.

Prim Care Companion CNS Disord 2011;13(3):e1-e9

© Copyright 2011 Physicians Postgraduate Press, Inc.

Submitted: November 6, 2010; accepted November 10, 2010.

Published online: May 5, 2011 (doi:10.4088/PCC.10m01082).

Corresponding author: Yasuyuki Okumura, PhD, Department of Social Psychiatry, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-Higashi cho, Kodaira 187-8553, Tokyo, Japan ([email protected]).

Major depressive disorder constitutes a major public health concern. The Global Burden of Disease study has revealed that overcoming depression is a high priority in all areas of the world.1,2 Depression has been projected to become the second leading cause of disease burden in the world by the year 2030,1 due to its high prevalence, high impact on functioning, and early-age onset.2 Furthermore, the disease burden of depression also produces an economic burden on society. A systematic review of 24 cost-of-illness studies of depression has reported that depression has substantial economic consequences on society.3 These cost-of-illness studies can not only quantify the economic burden of diseases but also help both the general public and policymakers to better understand the need to invest in health care and drive decisions about future insurance benefits, efforts in curbing and controlling diseases, and development of interventions.4,5 Over time, estimates from cost-of-illness studies have been used in cost-benefit and cost-effectiveness analyses to evaluate more effective interventions.4,5

Luppa et al3 have systematically reviewed studies estimating the annual national cost of depression, while pointing out some of the limitations of previous studies. First, most of the previous studies focused on only a narrow array of cost components, although cost-of-illness studies should consider such cost components as direct medical costs, depression-related suicide costs, and workplace costs; there are especially few studies that estimate depression-related suicide costs. Second, most of the studies were conducted in the United States or the United Kingdom; little information is available from central or eastern Europe, Africa, or Asia. To our knowledge, only 1 study has estimated the annual national cost of depression in Asia.6

The aim of the present study was to estimate direct medical costs, depression-related suicide costs, and workplace costs of major depressive disorder among adults 20 years and older in Japan in 2008.

METHOD

Cost-of-Illness Methodology

A top-down costing approach carried out on the basis of national health statistics was applied to estimate the annual national cost of depression among adults 20 years and older in Japan in 2008. We provide brief descriptions of major national health statistics in Appendix 1 to help readers better understand the methods used to estimate the annual national cost. From the societal perspective, the costs examined in the present study were direct medical costs, depression-related suicide costs, and workplace costs for all members of society. Direct medical costs included both inpatient and outpatient medical costs, while workplace costs included those related to both absenteeism (ie, productivity loss due to absence from the workplace) and presenteeism (ie, reduced productivity at the workplace due to depression). To compare the results of this study to the relevant findings of published cost-of-illness studies of depression, we calculated the annual national cost as costs per country and as costs per depressed individual based on the prevalence of depression7-9 and population size of individuals 20 years and older.10 All costs reported here are in 2008 US dollars, which were calculated using purchasing power parity (US$1.00 = JPNÂ¥117).11 All data and R syntax12 used to calculate costs are available from the first author upon request.

Direct Medical Costs

Inpatient medical costs were estimated as the product of 2 components: the annual number of inpatient admissions and the average costs per day of inpatient depression treatment. The annual number of inpatient admissions was calculated by multiplying the estimated number of inpatients per day by the 366 days in 2008. First, the estimated number of inpatients with a primary diagnosis of major depressive disorder (ICD-10 diagnostic code: F32-F33) per day across all age groups was retrieved from the Patient Survey 2008,13 conducted by the Ministry of Health, Labor and Welfare (MHLW). The estimated number of inpatients by age and specific diagnosis of depression is not available from the Patient Survey (ie, we could only obtain the estimated number of inpatients by age group with any mood disorder rather than with major depressive disorder); therefore, we estimated the percentage of inpatients 20 years and older with a primary diagnosis of any mood disorder (ICD-10 diagnostic code: F30-F39) from the Patient Survey and applied this percentage to the estimated number of inpatients with major depressive disorder. Second, the average costs, including nonpharmacy and pharmacy costs, per day for inpatient depression treatment were retrieved from the Survey of Medical Care Activities in Public Health Insurance 2008 (SMCA-PHI),14 conducted by the MHLW. Because the average costs per day are not reported in the SMCA-PHI 2008 by either age group or specific diagnosis of depression,14 we retrieved the average costs arising from inpatients with a primary diagnosis of any mood disorder across all age groups.

Outpatient medical costs were the product of the annual number of outpatient admissions and the average costs per day for outpatient depression treatment. The annual number of outpatient admissions was calculated as the product of the estimated number of outpatients per day and the 247 working days in 2008. As with the inpatient medical costs, we retrieved the estimated number of outpatients per day from the Patient Survey 200813 and the average nonpharmacy costs per day for outpatient depression treatment from the SMCA-PHI 2008.14 For patients who take prescriptions from an outside pharmacy, the average pharmacy costs per day are not reported by type of illness in the SMCA-PHI 200814; hence, we retrieved the average pharmacy costs arising from outpatients who take prescriptions from an in-house pharmacy and who have a primary diagnosis of any mood disorder across all age groups.

Depression-Related Suicide Costs

Depression-related suicide costs were estimated as the product of 2 components: the annual number of suicides due to depression and the net present value (NPV) of an individual’s future earnings with gender and age taken into account. First, the annual number of suicides was retrieved from the Criminal Statistics in 200815,16 and data were stratified by gender and age. The annual number of suicides due to depression is available only for individuals with an established cause of death in the Criminal Statistics in 2008.16 Therefore, we estimated the percentages of suicides due to depression by gender and age, using information from individuals with an established cause; we then applied this percentage to the annual number of suicides.

Second, we computed the NPV of an individual’s future earnings by age group for both men and women using the following formula:

where q is the age of the individual at death, n is the age if the individual had survived, Pq(n) is the probability that a person of age q will survive to age n, Xn is the average labor force participation rate in the age group with midyear age n, Wn is the average annual earnings in an age cohort with the midpoint n, and i is the annual discount rate. The NPV was estimated based on life expectancies from the Abridged Life Tables for Japan 2008,17 the average labor force participation rate from the Labor Force Survey 2008,18 the average annual earnings from the Basic Survey on Wage Structure 2008,19 and the annual discount rate of 6% from the previous cost-of-illness studies of depression.20,21

Workplace Costs

We computed the absenteeism costs by age group for both men and women using the following formula:

Absenteeism = Npop ×— Prdep ×— [0.271 ×—33days +
(1 – 0.271) ×— 60.2days] ×— 247days/366days ×— X ×— W

where Npop is the population size, Prdep is the 12-month prevalence of depression, 0.271 is the treatment rate for depression, 33days is the lost days due to treatment for depression among those treated, 60.2days is the lost days at home in bed among those untreated, 247days/366days is the proportion of working days in 2008, X is the average labor force participation rate, and W is the average wage per day. In addition, we computed presenteeism costs as follows:

Presenteeism = Npop ×— Prdep ×— [0.272 ×— 51days +
(1 – 0.271) ×— 65.8days] ×— 247days/366days ×— X ×— W ×— 0.20

where 51days is the reduced productivity days among those treated, 65. 8days is the reduced productivity days among those untreated, and 0.20 is the impairment rate, which equals the proportion of income loss due to depression.

Workplace costs were estimated using the following sources. First, the population size (Npop) was retrieved from the Population Estimates 200810 and data were stratified by gender and age. Second, the 12-month prevalence (Prdep) and the treatment rate (0.271) for DSM-IV major depressive disorder were retrieved from the World Mental Health Japan Survey 2002-2003.7-9 Because the 12-month prevalence in the World Mental Health Japan Survey is not available by gender and age group (ie, we could only obtain the 12-month prevalence by gender and the 12-month prevalence by age group), we assume that the same gender distribution for major depressive disorder can be applied to each age group (ie, 23.9% male and 76.1% female).7-9 Third, with regard to lost days (33days for treated individuals and 60.2days for untreated individuals), reduced productivity days (51days for treated individuals and 65.8days for untreated individuals), and impairment rate of 0.20, we maintained the same assumptions used in the previous cost-of-illness studies of depression.20,21 Fourth, the average labor force participation rates (X) were retrieved from the Labor Force Survey 2008.18 Finally, the average wage per day (W) was retrieved from the Basic Survey on Wage Structure 2008.19

Sensitivity Analyses

We performed 1-way sensitivity analyses to examine the extent to which results are affected by the choice of parameters used in the cost calculation. In more detail, we evaluated the sensitivity of the annual national cost of depression to different 12-month prevalence rates for depression (3.7% and 2.2%), treatment rates for depression (41.4% and 27.1%), percentages of suicides due to depression (60% and 27.6%), alternative discount rates (3% and 6%), different definitions of depression (any mood disorder and major depressive disorder), and target age ranges (all ages and age ≥ 20 years).

RESULTS

The annual national cost of depression in Japan was estimated at approximately $11 billion, in 2008 US dollar terms. This total cost corresponds to a cost of $4,836 per depressed individual.

Direct medical costs of depression in 2008 amounted to $1,570 million, or 14.2% of the total cost associated with this disease (Table 1). The costs of outpatient depression treatment ($918 million) were higher than those of inpatient treatment ($653 million). Pharmacy costs were estimated at $451 million, accounting for 28.7% of direct medical costs.

Depression-related suicide costs in 2008 amounted to $2,542 million, or 23.1% of the total cost (Table 2). A total of 31,414 suicides occurred in 2008 among adults aged ≥ 20 years. While the annual number of suicides was higher in men (22,246) than in women (9,168), the estimated annual number of suicides due to depression was about the same for men (4,572) and women (4,029). The male population aged 30-49 years constituted 43.6% of all depression-related suicide costs, because of the relatively high annual number of suicides due to depression within this demographic and the NPV of these individuals’ future earnings.

Workplace costs in 2008 amounted to $6,912 million, or 62.7% of the total cost (Table 3). Among workplace costs, absenteeism costs comprised $5,602 million or 81.0% of workplace costs, while presenteeism costs were estimated at $1,311 million (19.0%). The population aged 20-34 years constituted 43.3% of workplace costs, because of the relatively high prevalence of depression within this demographic.

Table 4 shows the results of 1-way sensitivity analyses that considered the impact of varying the key assumptions involved. The most sensitive assumption was the 12-month prevalence for depression: in varying the prevalence from 2.2% to 3.7%, the total cost increased from $11 billion to $16 billion (ie, a 48.6% increase). The second most sensitive assumption was the definition of depression. We changed the definition of depression from major depressive disorder to any mood disorder, and doing so resulted in a total cost of $16 billion, or a 45.2% increase. The third most sensitive assumption was the percentage of suicides due to depression; we changed the percentage from 27.6% to 60.0%, which resulted in a total cost of $14 billion, or a 30.6% increase.

DISCUSSION

The economic burden of depression in Japan in 2008 was approximately $11 billion, with $1,570 million relating to direct medical costs, $2,542 million to depression-related suicide costs, and $6,912 million to workplace costs. To compare the results of the present study to relevant findings from other published works, we conducted a MEDLINE review of English-language cost-of-illness studies published from 1966 to 2010 that estimate the annual national cost of depression using the following keywords: burden-of-illness or cost-of-illness or economic burden and depression or depressive disorder. We also screened the reference lists of all selected articles. Table 5 provides an overview of 10 published studies, together with the results of the present study.6,20-28 To establish comparability, costs reported in the published works were (1) inflated to the year 2008 using country-specific gross domestic product inflators29,30 and then (2) converted into US dollars using purchasing power parities.11,30 In addition, because countries differ in terms of prevalence for depression, we calculated the annual national cost as costs per depressed individual, based on the prevalence of depression reported in the studies and the country’s population size in the year of pricing.30,31 Although these adjustments may improve comparability of several annual national costs, the results of these adjustments must be interpreted with caution because any changes in parameters used to estimate costs in each study may influence current annual national cost (eg, changes in treatment rates or annual number of inpatient admissions).

Compared to previously published studies, we adopted conservative key assumptions; this may have resulted in a conservative estimate of the annual national cost of depression (Table 5). First, we assumed a relatively low prevalence of depression.7,9 Although epidemiologic studies revealed lower prevalence estimates of depression in Asian countries than in Western countries, these prevalence estimates are likely to be conservative because of sample selection bias and reporting bias.32 Second, we used a strict definition of depression as major depressive disorder. In contrast, most other studies estimated the annual national cost of depression by including individuals who exhibited any mood disorder. Third, we assumed a relatively low percentage of suicides due to depression, based on information regarding individuals with an established cause of death.16 In any case, the estimated percentage of suicides due to depression would be conservative, due to the generally low treatment rate and underdiagnosis of depression.8,33 In addition, the sensitivity analyses revealed that the aforementioned assumptions had a large impact on the annual national cost of depression.

In the present study, direct medical costs per depressed individual amounted to $689 (Table 5). This result is much lower than those reported in the United States ($1,195 to $1,400),20,21,25 with the exception of the study by Stoudemire et al ($507).26 One possible explanation for the discrepancy is that, on the one hand, health price levels in the United States are 25% higher than the Organization for Economic Cooperation and Development (OECD) average, while on the other hand, health price levels in Japan are 25% below that average.34 In addition, pharmacy costs in the present study represented 28.7% of direct medical costs; this share is higher than those reported in Europe (22%)28 and Sweden (19%),27 but lower than those in the United States (40%),20 China (59%),6 or the United Kingdom (84%).22 It is not clear why the share of pharmacy costs varies so widely. However, there are several potential explanations to account for the discrepancies of the pharmacy costs’ share. One possibility is that changes in patterns of care are associated with a shift wherein the highest contributor to costs became pharmacy costs, rather than inpatient treatment costs.20,22 Other possibilities are that higher prices of patented drugs may increase the share of pharmacy costs, while higher utilization rates of generic drugs may reduce the share. These possibilities, however, are too complicated to explain the discrepancies of the pharmacy costs’ share (ie, 40% of direct medical costs in the United States and 29% in Japan), because the average ex-manufacturer prices of patented drugs in the United States are 18% higher than those in Japan and the utilization rates of generic drugs in the United States (86%) are also higher than those in Japan (13%).35

In the present study, depression-related suicide costs per depressed individual amounted to $1,115, which is higher than the amount reported in the other countries—even while making conservative key assumptions in the present study (Table 5). One possible explanation for the discrepancy is that suicide rates per 100,000 individuals are much higher in Japan (28.1 for men and 10.4 for women) than the OECD average (17.6 for men and 5.2 for women).31

In the present study, workplace costs per depressed individual amounted to $3,032, which accounted for 62.7% of the total cost (Table 5). Despite underlying differences in key assumptions, workplace costs are the single largest cost category: they comprise 54%-90% of the total costs in previous studies, with the exception of the study by Rice and Miller (7.5%).25 The workplace costs per depressed individual ranged from $2,400 to $5,800, when ignoring outliers (Table 5). Our results suggest that strategies for identifying depressed workers and promoting effective treatment may reduce substantial workplace costs.36 In addition, educational campaigns for depression would have an important role in improving treatment rates and adherence rates,37 because individuals have less ability to recognize depression and have greater negative attitudes toward depression in Japan than in Australia.38,39

The results of the present study also point to the annual national cost of depression and underscore the importance of depression to Japanese society, especially compared to the economic burden posed by other diseases. Nonetheless, little has been reported on the annual national cost-of-illness in Japan.40,41 Nishimura and Zaher40 estimated that the annual national cost of chronic obstructive pulmonary disease was $6.8 billion, with $5.5 billion and $1.4 billion due to direct medical costs and workplace costs, respectively. In addition, Toyokawa et al41 reported that the annual direct medical costs of all liver diseases amounted to $6.2 billion. The estimated annual national cost of depression ($11 billion) is much higher than those of chronic obstructive pulmonary disease or of liver diseases.

The present study has several potential limitations. First, we excluded from estimations of direct medical costs patients with a secondary diagnosis of depression. Several epidemiologic studies have identified depression as commonly cooccurring with chronic physical health problems such as diabetes, hypertension, heart problems, stroke, cancer, arthritis, chronic obstructive pulmonary disease, asthma, kidney disease, liver disease, end-stage renal disease, and multiple sclerosis.42 In nonpsychiatric settings, less than half of the patients with depression are recognized by their physicians.33 Therefore, including only individuals with a primary diagnosis of depression may lead to an underestimation of direct medical costs. Second, we could not separate psychotherapy costs from nonpharmacy costs because of the lack of available data. Psychotherapy is one of the most effective treatments for depression in the international treatment guidelines.42,43 The share of psychotherapy costs in direct medical costs, however, may be negligible because only 28% of the Japanese medical institutions that employed 1 or more psychiatrists adequately provide psychotherapy.44 Third, by using a top-down costing approach based on Japanese national health statistics, it is difficult to include outside medical services such as those involving private counseling rooms, telephone counseling lifelines, or mental health welfare centers. Fourth, we used somewhat ambiguous assumptions in estimating workplace costs, due to data unavailability. We made the same assumptions used in previous studies20,21 concerning lost days due to depression, reduced productivity days due to depression, and impairment rates. In addition, we assumed the same 12-month prevalence and treatment rate for depression in 2002-2003 as in the year 2008.7-9

In conclusion, major depressive disorder imposes a substantial economic burden on Japanese society. This heavy economic burden highlights the urgent need for policymakers to allocate resources toward implementing strategies that prevent and manage depression in the Japanese population.

Author affiliations: Department of Social Psychiatry, National Institute of Mental Health (Dr Okumura), National Center of Neurology and Psychiatry (Dr Higuchi), Tokyo, Japan.

Potential conflicts of interest: None reported.

Funding/support: None reported.

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