Published by Oxford University Press on behalf of the International Epidemiological Association

The Author 2013; all rights reserved. Advance Access publication 18 May 2013

International Journal of Epidemiology 2014;43:10541062

doi:10.1093/ije/dyt057

COHORT PROFILE

Cohort Profile: The Japan Diabetes

Complications Study: a long-term follow-up of
a randomised lifestyle intervention study of
type 2 diabetes
Shiro Tanaka,1 Sachiko Tanaka,2 Satoshi Iimuro,3 Hidetoshi Yamashita,4 Shigehiro Katayama,5
Yasuo Ohashi,3 Yasuo Akanuma,6 Nobuhiro Yamada7 and Hirohito Sone8*; on behalf of the Japan
Diabetes Complications Study Group
1

Department of Clinical Trial Design and Management, Translational Research Center, Kyoto University Hospital, Kyoto, Japan,
EBM Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan, 3Department of Biostatistics, School of Public
Health, University of Tokyo, Tokyo, Japan, 4Department of Ophthalmology, Yamagata University Faculty of Medicine, Yamagata,
Japan, 5Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Saitama, Japan, 6Institute for
Adult Diseases, Asahi Life Foundation, Tokyo, Japan, 7Department of Internal Medicine, University of Tsukuba Institute of Clinical
Medicine, Tsukuba, Ibaraki, Japan and 8Department of Internal Medicine, Niigata University Faculty of Medicine, Niigata, Japan

*Corresponding author. Department of Internal Medicine, Niigata University Faculty of Medicine, 1-757 Asahimachi-dori, Chuoh-ku,
Niigata, 951-8510, Japan E-mail: jdcstudy@md.tsukuba.ac.jp

Accepted

11 March 2013
The Japan Diabetes Complications Study, a randomised lifestyle
intervention study of type 2 diabetes conducted at 59 institutes
throughout Japan that enrolled 2033 eligible patients from
January 1995 to March 1996, was directed at: (i) determining the
incidence and progression rates of complications of diabetes; (ii)
exploring clinical risk factors for complications of diabetes; and
(iii) determining the association between lifestyle factors, including
diet and physical activity, and complications of diabetes, in addition
to comparing, in a randomised manner, the effects on type 2 diabetes of an extensive lifestyle intervention and conventional treatment. The protocol for the study originally specified four study
populations according to primary outcomes, consisting of: (1) a
macroangiopathy group (N 1771); (ii) a nephropathy group
(N 1607); (iii) a retinopathy-incident group (N 1221); and (iv)
a retinopathy-progression group (N 410). The primary outcomes
were: (i) development of retinopathy; (ii) progression of retinopathy; (iii) development of overt nephropathy; and (iv) occurrence of
macroangiopathic events including proven coronary heart disease
and stroke. The study was originally planned to follow patients
for 8 years, and an extended follow-up is ongoing. Information
about primary outcomes, laboratory tests, and other clinical variables for each patient was collected at a central data centre through
an annual report from each investigator. Additionally, extensive
lifestyle surveys were conducted at baseline and 5 years after the
beginning of the study intervention in both the intervention and
conventional treatment groups. A description of the occurrence of
complications of diabetes and of all-cause mortality, provided in
this paper, demonstrated a clear gender-based difference in
1054

THE JAPAN DIABETES COMPLICATIONS STUDY

1055

cardiovascular disease and all-cause mortality. The data set of the

study is not freely available, but collaborative ideas are welcome.
Potential collaborators should discuss ideas informally with the
principal investigator by e-mail.
Keywords

Cardiovascular disease, dietary survey, nephropathy, physical

activity, retinopathy

Why was the cohort set up?

Lifestyle interventions, including those of diet, exercise,
or both, play a crucial role in the prevention and care of
diabetes, and can prevent type 2 diabetes1 as well as
ameliorate glycaemia and other risk factors for complications27 in patients with established diabetes.
However, the effects of these interventions on complications of diabetes remain unknown, although a few
studies have been done8,9 of lifestyle modification in
combination with pharmacotherapy for hyperglycaemia, hypertension, and dyslipidaemia in patients
with type 2 diabetes. In this context, the Japan
Diabetes Complications Study (JDCS) (RCT registration
number C000000222 at www.umin.ac.jp), an openlabel, randomised clinical trial of Japanese patients
with type 2 diabetes, was set up to clarify whether a
long-term therapeutic intervention focused mainly on
lifestyle education would have an effect on the incidence of events involving macro- and microvascular
complications of type 2 diabetes in patients with established type 2 diabetes.10 A primary analysis of the randomised comparison, done at the 8-year follow-up,10
showed that the incidence rate of stroke in the intervention group was significantly lower than in the conventional treatment group [hazard ratio (HR): 0.62, 95%
confidence interval (CI): 0.390.98, P 0.04], and that
the incidence rates of coronary heart disease, retinopathy, and nephropathy did not differ significantly in the
two groups. The JDCS accordingly concluded that lifestyle modification had a significant effect on stroke incidence in patients with established type 2 diabetes.
In addition to the randomised comparison of a
long-term therapeutic intervention vs. conventional
treatment for type 2 diabetes, the JDCS sought to:
(i) determine the incidence and rates of progression
of complications of diabetes; (ii) explore clinical risk
factors for complications of diabetes; and (iii) determine the association of lifestyle factors, including diet
and physical activity, with complications of diabetes.
The study therefore included extensive lifestyle surveys at baseline and at 5 years, and an extended
follow-up period. This paper reports the findings of
the JDCS as an ongoing cohort study.

Who is in the cohort?

The eligibility criteria for the JDCS were: (i) a previous diagnosis of type 2 diabetes; (ii) an age of 4070

years; and (iii) a blood concentration of hemoglobin

A1C (HbA1C) of 5 6.5%. Diabetes mellitus and impaired glucose tolerance (IGT) were diagnosed according to the Report of the Committee of the Japan
Diabetes Society on the Classification and Diagnostic
Criteria of Diabetes Mellitus, in which the cut-off
values for glucose levels are almost identical to
those of the World Health Organization (WHO).
From January 1995 to March 1996, the study enrolled, as its initial population, 2205 patients (mean
age 58.6 years; 47% women) from outpatient clinics in
59 university and general hospitals throughout Japan
that specialise in diabetes care (Figure 1). Before April
1996, when the interventional phase of the study
began, patients who did not meet the eligibility criteria were excluded, leaving 2033 patients (92%) who
were randomised to the intervention group (N 1017)
or to the conventional treatment group (N 1016).
This was the overall study population used in future
analyses.
Throughout the study period, patients in both the conventional therapy and intervention groups received the
same treatment that they had before the start of the
study, with therapeutic management during the study
being provided by specialists in diabetes. This included
dietary advice by an administrative dietician on the
basis of the Food Exchange Lists Dietary Guidance for
Persons with Diabetes.11 In addition to this routine conventional treatment, patients in the intervention group
were provided with education through individual counselling on dietary habits, physical activities, and adherence to treatment, including the proper use of
medicines. Counselling was provided by physicians,
nurses, dieticians, and other health-care staff members
during each outpatient clinic visit. Patients in the intervention group also received 15-minute telephone counselling sessions at least once every 2 weeks from nurses,
dieticians, and psychotherapists trained in diabetes
education. These telephone sessions were based on a
structured and uniform format. A diary to record laboratory and other data during the study
was distributed to the patients in the intervention
group to provide better feedback on therapeutic
results. A pedometer was also given to patients in the
intervention group for objective assessment of their exercise. Goals were set for patients in the intervention
group and their physicians, including an HbA1c
level < 6.5%, body mass index (BMI) < 22 kg/m2, blood
pressure (BP) < 140/85 mmHg, serum cholesterol

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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY

University hospital
General hospital

Figure 1 Outpatient clinics at 59 university and general hospitals nationwide in Japan that specialise in diabetes care

level < 220 mg/dL, serum triglyceride level < 150 mg/dL,
serum high-density lipoprotein (HDL) cholesterol440 mg/dL, waist-to-hip ratio < 0.9 for men
and < 0.8 for women, smoking cessation, and abstinence from alcohol. The goals for BP and serum cholesterol levels were updated in accordance with the
revision of guidelines made by the Japan Diabetes
Society (JDS), which were < 130/80 mmHg and
< 220 mg/dL, respectively.
The protocol for the JDCS originally specified four
analysis populations according to primary outcomes
(Figure 2). The macroangiopathy group consisted of
1771 patients after the exclusion of patients with a
history of angina pectoris, myocardial infarction,

stroke, peripheral arterial disease, familial hypercholesterolaemia, or type III hyperlipidaemia. The nephropathy group was originally defined as the analysis
population for incident overt nephropathy among
patients with normo or low microalbuminuria. This
analysis population consisted of 1558 patients after
the exclusion of those with non-diabetic nephropathy,
nephrotic syndrome, serum creatinine levels
4120 mmol/L, or a mean value of two spot urine examinations that showed an albumin excretion rate of
<150 mg/g creatinine.12 In future analyses, in which
incident overt nephropathy from high microalbuminuria can be of secondary interest, we plan to
extend the nephropathy group by including 49

THE JAPAN DIABETES COMPLICATIONS STUDY

Nephropathy group
(N = 1607)

N = 16
Not included in any groups
(N = 54)

N = 167

N = 158
N = 1266

about primary outcomes, laboratory test results, and

other clinical variables for each patient was collected
at a central data centre through an annual report
from each examining physician. Extensive lifestyle
surveys were also conducted at baseline and 5 years
after the beginning of the study intervention in both
study groups. Table 3 summarises all of the measurements made and data collection used in the JDCS.

N = 25

N = 174

What has been measured?

N = 173
Macroangiopathy group
(N = 1771)

1057

Retinopathy-incident and
retinopathy-progression groups
(N = 1221 + 410)

Figure 2 The four analysis populations in the JDCS

according to primary outcomes

patients with an albumin excretion rate of 150 to

300 mg/g creatinine. The retinopathy-incident group
consisted of 1221 patients after the exclusion of candidates who had retinopathy or a major ocular disease
(e.g., glaucoma, dense cataract, or a history of cataract surgery). The retinopathy-progression group consisted of 410 patients after the exclusion of those in
the retinopathy-incident group who had a pre-proliferative or proliferative retinopathy or a major ocular
disease (e.g., glaucoma, dense cataract, or a history of
cataract surgery).
Figure 3 is a flow diagram of the data collection and
follow-up populations in the JDCS. The overall 8-year
follow-up rate was 73%; 1305 patients were followed
in the eighth year of the study, 80 patients retracted
informed consent, and 97 patients died before the
eighth year of follow-up. Of the patients eligible for
enrollment in the JDCS, 1588 patients (78%) responded to the baseline dietary survey and 1207
(76%) of these responding patients completed the 8year follow-up, leaving 381 patients for whom dietary
data had been available but who did not complete the
8-year follow-up. Table 1 compares baseline characteristics of the entire study cohort (1087 men and 946
women) with those for whom no baseline dietary
data were available (N 445), and those who were
not followed for 8 years (N 551). The mean age
and HbA1c concentration of the patients without baseline dietary data and those not followed for 8 years
were similar to those of the entire study cohort. The
prevalence of diabetic retinopathy was relatively low
in the patients without baseline dietary data.

How often have they been

followed?
We originally planned to follow patients for 8 years,
and an extended follow-up is ongoing. Information

Primary outcomes
Primary outcomes of the JDCS consisted of microand macro-vascular complications. Retinopathy was
evaluated by qualified ophthalmologists at each participating institution, using the classification designed
for this research, as follows: (i) stage 0, no retinopathy; (ii) stage 1, haemorrhage and hard exudates;
(iii) stage 2, soft exudates; (iv) stage 3, intraretinal
microvascular abnormalities and venous changes
including beading, loops, and duplication; and (v)
stage 4, new vessels, vitreous haemorrhage, fibrous
proliferation, and retinal detachment. The retinopathy
endpoints were; (i) development of retinopathy (from
stage 0 to any other stage confirmed in two continuous years); and (ii) progression from stage 1 to stage
3 or 4. The nephropathy endpoint was defined as the
development of overt nephropathy (spot urinary albumin excretion 4300 mg/g creatinine in two consecutive samples). Macroangiopathy endpoints included
the incidence of definite coronary heart disease
(angina pectoris or myocardial infarction) or stroke.
Diagnosis of angina pectoris and myocardial infarction was made according to criteria defined by the
WHO/ Multinational Monitoring of Trends and
Determinants in Cardiovascular Disease (MONICA)
project, and diagnosis of stroke was made according
to guidelines defined by the Ministry of Health,
Labour and Welfare of Japan.13 Adjudication of endpoints was done by central committees consisting of
experts in each complication, on the basis of additional data such as findings on computed tomography (CT) or magnetic resonance imaging (MRI) of
the brain or sequential changes in electrocardiograms.
Dietary survey
Food Frequency Questionnaires based on food groups
(FFQg)14 and 24-hour dietary records were collected at
baseline and 5 years after the beginning of the study
intervention from both the intervention and conventional treatment groups. In brief, the FFQg consists
of items about 29 food groups and 10 kinds of cookery
and elicits information about the average intake per
week of each food or food groups in commonly used
units or portion sizes. The FFQg was externally validated through a comparison with weighed dietary records for 7 continuous days of 66 subjects aged 1960
years.14 The coefficients of correlation of the FFQg with

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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY

2033 patients with type 2 diabetes

No. unretrieved
case records
Year 1 13
Year 2 40
Year 3 40
Year 4 47
Year 5 28
Year 6 58
Year 7 33
Year 8 50

Control group
N = 1016

Intervention group
N = 1017

Followed in year 8: 624

Retracted informed consent: 40
Died: 43

Followed in year 8: 681

Retracted informed consent: 40
Died: 54

No. unretrieved
case records
Year 1 10
Year 2 24
Year 3 29
Year 4 31
Year 5 35
Year 6 52
Year 7 28
Year 8 33

Figure 3 Flow diagram of data collection and follow-up in the JDCS

Table 1 Comparison of baseline characteristic of patients in the entire cohort, those with no baseline dietary data, and
those not followed for 8 years
Men in the entire
cohort
(N 1087)
Age (year)
HbA1c (%)

Mean
58.1

SD
7.0

Women in the
entire cohort
(N 946)

No baseline
dietary data
(N 445)

Not followed
for 8 years
(N 551)

Mean
59.0

Mean
57.9

Mean
58.4

SD
6.8

SD
7.1

SD
7.1

7.7

1.2

8.1

1.4

7.8

1.2

8.0

1.4

Fasting blood sugar (mg/dL)

158.9

41.4

161.3

45.4

158.6

42.8

164.1

45.4

Years after diagnosis (year)

11.5

7.7

10.2

6.6

10.7

7.7

10.8

7.6

Diabetic retinopathy (%)

19.0%

Weight (kg)

62.5

8.8

54.4

8.3

59.9

10.0

59.0

9.5

BMI (kg/m2)

22.8

2.7

23.3

3.4

23.4

3.2

23.1

3.0

Waist circumference (cm)

82.3

7.8

76.6

9.6

80.5

9.6

80.1

9.1

Waist-to-hip ratio

0.89

21.5%

0.06

0.84

13.0%

0.07

0.88

17.2%

0.08

0.87

0.08

SBP (mmHg)

131.1

15.7

132.4

16.9

131.7

16.8

131.2

15.9

DBP (mmHg)

77.3

9.9

76.3

10.1

77.4

10.2

76.9

9.5

Total cholesterol (mg/dL)

194.5

34.5

209.4

33.7

203.9

35.1

202.8

36.2

LDL-C (mg/dL)

116.7

32.5

129.2

30.9

123.2

32.7

124.1

33.4

HDL-C (mg/dL)
Triglyceridesa (mg/dL)

52.3

16.5

57.2

16.7

54.5

16.2

54.4

16.8

130.2

85.4

99.0

71.0

109.0

87.0

104.0

69.0

LP(a)a (mg/dL)

22.8

27.2

17.0

19.6

17.0

19.8

16.0

21.0

Spot urine ACRa (mg/gCr)

60.6

271.3

18.5

31.6

20.2

44.0

20.4

41.5

eGFR (mL/min/1.73m2)

85.3

28.5

88.6

29.2

85.0

24.8

87.6

27.5

Treated with insulin (%)

19.5%

22.5%

21.9%

17.7%

Treated with OHA without insulin (%)

64.2%

66.7%

64.5%

65.7%

Treated with antihypertensive agents (%)

22.4%

32.8%

28.2%

27.1%

Treated with agents for dislipidaemia (%)

16.7%

35.1%

27.8%

24.4%

Current smoker (%)

44.7%

8.8%

26.7%

31.6%

Abbreviations: ACR: albumin-to-creatinine ratio; BMI: body mass index; DBP: diastolic blood pressure; eGFR: estimated glomerular
filtration rate; HDL-C: high-density lipoprotein cholesterol; LDL-C: low-density lipoprotein cholesterol; Lp(a): lipoprotein(a); OHA:
oral hypoglycemic agents; SBP: systolic blood pressure.
a
Median and interquartile range.

THE JAPAN DIABETES COMPLICATIONS STUDY

dietary records for energy, protein, fat, carbohydrate, and

calcium intakes were 0.47, 0.42, 0.39, 0.49, and 0.41, respectively. The intakes of 26 of 31 nutrients usually estimated in dietary surveys were not significantly different
with the two methods according to 5 paired Students
t-tests.14 The ratio of the value obtained by dividing the
FFQg by the dietary records ranged from 72% (vitamin
B12) to 121% (vitamin C). The average value of this ratio
was 104%. After patients completed the questionnaire,
the dietician checked the sheets in an interview. To calculate nutrient and food intakes, we use standardised
software for population-based surveys and nutrition
counselling in Japan (Excel EIYO-KUN version 4.5;
University Nutrition Database), which is based on the
Standard Tables of Food Composition in Japan15 edited
by the Japanese Ministry of Education, Culture, Sports,
Science, and Technology.

Physical activity survey

Leisure-time physical activity was assessed at baseline
through a self-administered questionnaire, which was
almost identical to that used and validated in the
Health Professionals Follow-up Study.16 Patients were
asked the average frequency (times per week) and duration (minutes per one time) of their normal walking,
brisk walking, jogging, golfing, tennis, swimming, aerobics dancing, cycling, and other miscellaneous exercises
(specified by each patient). The duration of each activity
in minutes was multiplied by the typical energy expenditure for the activity expressed in metabolic equivalents
(METs) on the basis of the newest compendium of
Ainsworth,17 and this was then summed for all activities
to yield a MET-hour score per week. One MET, the
energy expended in sitting quietly, is equivalent to 3.5
mL of oxygen uptake per kilogram of body weight per
minute, or 1 kcal per kilogram of body weight per hour.
Occupation was surveyed with a self-administered
questionnaire based on the Japan Standard
Classification of Occupations,18 which was also used
in the National Health and Nutritional Examination
Survey19 in Japan. The occupational classifications in
the survey were: (i) professional or skilled workers
and technicians; (ii) administrative or managerial
workers; (iii) office or clerical workers; (iv) sales
workers; (v) service workers; (vi) armed force and
police occupation; (vii) agricultural, forestry and fishery workers; (viii) workers in transport, trades and
storage; (ix) labourers in manufacturing, mining,
and construction; (x) no work or housewives.
Physical activity was determined with Baeckes Total
Physical Activity Index20 at 5 years. The extent of physical activity at baseline and that according to Baeckes
index were significantly correlated (Spearmans rank
correlation coefficient, r 0.28; p40.01).
Laboratory tests and clinical variables
Other measurements included treatments, physical
examinations, blood pressure, neurological/ophthalmological examinations, and laboratory tests such as

1059

for HbA1c, fasting plasma glucose/insulin/C-peptide,

serum lipids/creatinine/urea nitorogen, and urine analysis. Assays for HbA1c assays are standardised by the
Laboratory Test Committee of the JDS in values established by the JDS; the US National Glycohemoglobin Standardization Program (NSGP) value of HbA1c
would be calculated as follows: 0.25 1.02  JDS
value.21 Diabetes-related distress and information
about cigarette smoking were collected through a
self-administered questionnaire.

Follow-up and response to lifestyle survey

The overall 8-year follow-up rate in the JDCS was
73% (Figure 3), and the follow-up rates in the macroangiopathy group, nephropathy group, retinopathy-incident group, and retinopathy-progression group were
75%, 78%, 77%, and 77%, respectively. At baseline,
and of the 2033 patients in the JDCS cohort, 1486
completed both the FFQg and the 24-hour dietary
record, 30 completed the FFQg only, and 72 completed the 24-hour dietary record only (overall response: 78%). Of the 1516 respondents to the
baseline measurement of FFQg, 998 (66%) completed
the FFQg at 5 years. Of the total of 2033 patients in
the study cohort, 1917 (94%) completed the questionnaire on physical activity. Of the 1917 respondents to
the baseline measurement of physical activity, 1217
(63%) completed the Baeckes Total Physical Activity
Index at 5 years.

What has it found? Key findings

and publications
Primary results of randomised comparison
The registration of patients in the JDCS was completed in March 1996, and the interventions for the
intervention group were continued until March 2003.
In the primary analysis of the randomised comparison
at the 8-year follow-up,1 the status of control of most
classic cardiovascular risk factors, including body
weight, glycaemia, serum lipids, and blood pressure,
did not differ in the two study groups, but the incidence rate of stroke in the intervention group (5.48/
1000 person-years) was significantly lower than that
in the conventional treatment group (9.52/1000
person-years) according to both KaplanMeier analysis (p 0.02) and multivariate Cox analysis (HR:
0.62, 95% CI: 0.390.98, P 0.04). The incidence
rates of coronary heart disease, retinopathy, and
nephropathy did not differ significantly in the two
study groups.
Diabetes complications and all-cause
mortality over 8 years
Table 2 shows the occurrence of complications of diabetes and all-cause mortality in the patients in the
JDCS who had type 2 diabetes. The crude incidence

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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY

rates per 1000 person-years of diabetic retinopathy in

men and women in the retinopathy-incident group
were 34.77 and 42.70, respectively. The crude progression rates of diabetic retinopathy in men and women
in the retinopathy-progression group were 17.65 and
24.75, respectively. The crude incidence rates of overt
nephropathy in men and women in the extended
nephropathy group were 9.47 and 7.40, respectively.
The crude incidence rates of cardiovascular disease
(coronary heart disease and stroke) in men and
women in the macroangiopathy group were 17.03
and 10.47, respectively. The all-cause mortality rates
in men and women in the overall JDCS cohort were
8.39 and 5.68, respectively.

Other publications
In addition to reporting its primary results,10 the
JDCS reported the pathophysiological characteristics
of East Asian patients with type 2 diabetes.2225 In a
3-year interim report, we found small but significant
differences in HbA1c levels in the intervention group
(7.62  1.20%) and conventional therapy group
(7.78  1.27%) that had appeared as early as 2 years
after the beginning of the intervention in the JDCS

and were maintained in the third year of the study.13

The transition rate from normo- and low microalbuminuria to overt nephropathy was 6.7/1000 personyears, and was significantly higher for the low microalbuminuric group than for the normoalbuminuric
group (18.5 and 2.3/1000 person-years, respectively).12 The rates of incidence and progression of
diabetic retinopathy were 38.3/1000 person-years
and 21.1/1000 person-years, respectively.26 The JDCS
also identified risk factors for cardiovascular disease
in Japanese patients.27 With regard to coronary heart
disease, the serum triglyceride concentration was a
leading predictor of disease, and was comparable to
the LDL cholesterol concentration in this regard
(HR per 1 SD increase in triglycerides: 1.54, 95%
CI: 1.221.94; HR per 1 SD increase in LDL cholesterol: 1.49, 95% CI: 1.251.78).28 These findings
showed that the observed incidence rates of microvascular complications in the Japanese study population were lower than those in the Caucasian
population and that the risk factors for complications
of diabetes can also differ, suggesting ethnic disparities in the aetiology of complications of diabetes in
the two populations. Further investigation is

Table 2 Crude incidence rates of diabetes complications and all-cause mortality over 8 years
Total
Incident retinopathy
Progression of retinopathy

Men

Women

N
1221

Event
325

CIR
38.27

N
671

Event
165

CIR
34.77

N
550

Event
160

CIR
42.70

410

65

13.88

207

28

17.03

203

37

10.47

Overt nephropathy

1607

96

8.48

842

56

9.47

765

40

7.40

Cardiovascular disease

1771

163

21.09

940

104

17.65

831

59

24.75

All-cause mortality

2033

98

7.11

1087

61

8.39

946

37

5.68

Abbreviation: CIR: crude incidence rate per 1000 person-years.

Table 3 Summary of data collection in the Japan Diabetes Complications Study

1996 to 1999

5 year follow-up (2000)

2001 and after

Background characteristics

Baseline (1995)
ADC

Clinical and laboratory measurementsa

ADC

ADC

ADC

ADC

Chest radiographs

ADC

ADC

ADC

ADC

Neurological examination

ADC

ADC

ADC

ADC

Urine testsb

ADC

ADC

ADC

ADC

Ophthalmological examination

ADC

ADC

ADC

ADC

Therapeutic measures

ADC

ADC

ADC

ADC

Electrocardiograms

ADC

ADC

ADC

ADC

Cardiovascular events

ADC

ADC

ADC

ADC

Lifestyle surveys

ADC

ADC

Abbreviation: ADC: annual data collection.

a
Body weight, waist circumference, hip circumference, blood pressure, fasting plasma glucose, HbA1C, insulin, C-peptide, and lipids,
measured at least semi-annually.
b
Serum creatinine, blood urea nitrogen, urine protein, and urine albumin, measured at least semi-annually.

THE JAPAN DIABETES COMPLICATIONS STUDY

therefore needed of the epidemiological associations

of clinical risk factors, lifestyle factors, and complications of diabetes in Asian population.

What are the main strengths and

weaknesses?
The main strengths of the JDCS are: (i) a nationally
representative patient population, in that the study
subjects were recruited from 59 university and general
hospitals throughout Japan; (ii) a follow-up done by
diabetes specialists annually, ensuring the accuracy
and quality of data, and especially of the primary outcome data; and (iii) relatively high response rates to
lifestyle surveys. There are points for improvement
as well. Calibration techniques for the dietary
survey, such as the use of a doubly-labelled water
method and multi-day 24-hour dietary records, were
unavailable. The sample size of the study was
small relative to population-based cohort studies, because it was based on the JDCS being a randomised
trial. Additionally, the laboratory tests in the study

1061

were conducted at its participating institutions and

not standardised prospectively, although laboratory
tests are well standardised on a nationwide level in
Japan.

Can I get hold of the data? Where

can I find out more?
All data management for the JDCS is conducted at a
central data centre in Tokyo. Our data set is not freely
available, but collaborative ideas are welcome.
Potential collaborators should discuss ideas informally
with the principal investigator, who takes responsibility for collaboration by e-mail (jdcstudy@md.
tsukuba.ac.jp).

Funding
The JDCS is financially supported by the Ministry of
Health, Labour and Welfare, Japan.
Conflict of interest: None declared.

KEY MESSAGES
 This study of 2033 Japanese patients with type 2 diabetes was originally established in 1995 as a
randomised lifestyle intervention trial. Its analysis of primary data at 8 years revealed a significant
effect of the intervention used in the study on the incidence of stroke but not of other macro- or
microvascular complications of diabetes.
 The study also aimed to explore epidemiological associations of clinical risk factors for diabetes, of
lifestyle factors with the complications of diabetes, and of complications of diabetes themselves.
Extensive lifestyle surveys, including surveys of diet and physical activity, were done at baseline
and at 5 years, and an extended follow-up is ongoing.
 Little is known about the effects of lifestyle factors on the prognosis of Asian patients with type 2
diabetes characterised by low body weight. Comparing our cohort, which is representative of
Japanese patients type 2 diabetes, with studies of Caucasian patients should provide further insights
into ethnic disparities in this disease.

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