Behavioral economics survey of patients with type 1 and type 2 diabetes

Figures & data

Table 1 Survey questionnaires

Question label	Construct	Text
QA	General risk proneness 1	Usually when you go out, how high does the probability of rain have to be before you take an umbrella or take a raincoat with you? More than [.….] %.
QB	General risk proneness 2	When you have a seat reservation for a train, how many minutes early do you usually arrive at the station? [.….] minutes before.
QC	Procrastination 1 (childhood)	Thinking about when you were a child and you were given an assignment during school vacation, how early did you usually finish up the assignment? 1. I tended to get it done early, before the due date. 2. I worked on it daily, up until the due date. 3. I tended to get it done toward the end.
QD	Procrastination 2 (now)	Thinking about yourself now, if you were given an assignment during school vacation, how early would you finish up the assignment? 1. I would get it done rather early, before the due date. 2. I would work on it daily, up until the due date. 3. I would get it done rather toward the end.
QE	Risk proneness	Suppose that there were a lottery worth 2,000 yen (USD 20) with a 50% chance of winning.
	Lottery 1 (low risk, low gain)	What is the most that you would pay for a lottery ticket? I would pay up to [.….] yen.
QF	Risk proneness Lottery 2 (high risk, high gain)	Suppose that there were a lottery worth 100,000 yen (USD 1,000) with a 1% chance of winning. What is the most that you would pay for a lottery ticket? I would pay up to [.….] yen.
QG	Endowment effect	You happen to find a ticket for a lottery with a 1% chance of winning 100,000 yen (USD 1,000). What’s the lowest price you would sell it for? No less than [.….] yen.
QH	Myopic time preference 1	Let’s assume you have two options to receive money. You may choose either receive 20,000 yen today or to receive a different amount 1 month from today. What is the lowest amount of money you would choose to receive 1 month from today, rather than receive 20,000 yen today. I would wait 1 month to receive the 20,000 yen (USD 200) if at least [.….] yen were added to it.
QI	Myopic time preference 2	How about if the amount you could receive today is 100,000 yen? What is the lowest amount of money you would choose to receive 1 month from today, rather than receive 100,000 yen today. I would wait 1 month to receive the 100,000 yen (USD 1,000) if at least [.….] yen were added to it.
QJ	Acceptance to uncertainty in effectiveness of medicine	A doctor tells you that the effectiveness of the medicine they are prescribing can vary among individuals, and that it may or may not end up working for your ailment. Would this explanation be sufficient for you?
		1. Yes 2. Probably 3. Not sure 4. Probably not 5. No
QK	Average spending on medical care	On average, how much do you spend on medical treatments every month? Monthly average: [.….] yen.
QL	Subjective risk estimation for cardiovascular disease (CVD)	Out of 100 people including yourself, how many of them do you think will have a heart attack or stroke within 10 years that makes you think you will also have a heart attack or stroke? [.….] people out of 100.
QM	Willingness to pay for a medicine reducing disease risk	Out of 100 people including yourself, say that 50 of them will have a heart attack or stroke within 10 years. A certain kind of medicine can reduce that number to 25. How much would you pay every month to continue taking that medicine? I would pay up to [.….] yen every month just for that medicine.
QN	General satisfaction to current life	How satisfied are you with your current life?
		1. Very 2. Above average 3. Moderately 4. Not much 5. Not at all
QO	Consciousness of disease	Do you have diabetes?
		1. Yes 2. No 3. Not sure
QP	Patient understanding of diabetes	Which of the following do you think most apply as factors in diabetes getting worse? 1. Lifestyle is a greater factor than genetics. 2. Lifestyle and genetics are roughly equal factors. 3. Genetics are a greater factor than lifestyle.
QQ	Family understanding of diabetes	The next question is only for diabetes patients. Does your family tell you that you have diabetes or your diabetes got worse because of your lifestyle?
		1. Yes 2. Maybe 3. No 4. I do not live with family

Table 2 Age-stratified patient characteristics

	Type 1	Type 2	P-value
Age under 45
Number of patients	32	17
Age (years)	36.3±1.1	37.6±1.5	0.4547
Male:female	10:22	11:6	0.0351
BMI (kg/m^2)	23.9±0.8	25.8±1.1	0.1694
Diabetes duration (years)	11.3±1.4	5.6±1.8	0.0173
HbA1c (% NGSP)	7.57±0.23	7.92±0.31	0.3671
Nephropathy rate (%)	9.8	23.5	0.1934
Retinopathy rate (%)	32.3	29.4	0.8388
Insulin treatment (%)	96.8	91.7	0.1870
Age 45–under 65
Number of patients	22	76
Age (years)	54.7±1.2	56.8±0.7	0.1280
Male:female	11:11	49:27	0.2198
BMI (kg/m^2)	22.7±0.9	26.4±0.5	0.0005
Diabetes duration (years)	10.4±1.3	10.3±0.7	0.9302
HbA1c (% NGSP)	7.48±0.26	7.57±0.14	0.7871
Nephropathy rate (%)	13.6	38.2	0.0308
Retinopathy rate (%)	18.1	56.8	0.0015
Insulin treatment (%)	90.9	60.0	0.0247
Age 65 or older
Number of patients	12	60
Age (years)	70.5±1.5	71.5±0.7	0.5399
Male:female	7:5	35:25	1.0000
BMI (kg/m^2)	23.7±1.2	24.9±0.6	0.3858
Diabetes duration (years)	20.0±3.1	14.8±1.4	0.1057
HbA1c (% NGSP)	7.49±0.38	7.29±0.16	0.6261
Nephropathy rate (%)	43.3	52.4	0.4822
Retinopathy rate (%)	33.3	46.5	0.4014
Insulin treatment (%)	25.0	43.0	0.2372

Note: Values are presented as mean ± SE.

Abbreviations: BMI, body mass index; HbA_1c, hemoglobin A_1c; NGSP, National Glycohemoglobin Standardization Program; SE, standard error.

Table 3 Age-stratified analysis of the survey response rate

	Type 1 diabetes				Type 2 diabetes
	Male		Female		Male		Female
	Response	Non-response	Response	Non-response	Response	Non-response	Response	Non-response
Patients number by age
Under 45	7	3	20	2	5	6	5	1
45–under 65	11	0	10	1	31	18	19	8
65 or older	6	1	4	1	29	6	21	4
Total patient number	24	4	34	4	65	30	45	13
Response rate by sex	85.7%		89.5%		68.4%		77.6%
Response rate by diabetes type	87.9%**				71.9%

Notes:

** Type 1 vs type 2, P<0.01 for Mantel–Haenszel analysis.

Table 4 Ordinal logistic regression analysisa of factors associated with retinopathy levelsb

Parameter	Estimate	Standard error	Chi-square test	P-valuee
Type (type 1)	−0.844	0.371	5.16	0.0232f
Sex (male)	0.311	0.269	1.33	0.248
Age	−0.0122	0.0237	0.27	0.6052
Diabetes duration	0.124	0.0336	13.7	0.0002g
HbA1cc	0.631	0.219	8.28	0.004g
BMI	−0.0566	0.0734	0.59	0.4407
Survey responsesd
QA: general risk proneness 1	−0.000605	0.0124	0	0.9611
QB: general risk proneness 2	−0.0106	0.0214	0.25	0.6195
QC[1]: procrastination 1	−0.508	0.513	0.98	0.3223
QC[2]	0.998	0.537	3.44	0.0635
QE: lottery 1 low risk, low gain	0.0000906	0.0000321	7.98	0.0047g
QG: endowment effect	0.0000114	0.00000869	1.73	0.1884
QH: myopic time preference 1	−0.0000482	0.0000205	5.52	0.0188f
QJ[2/1]: accept uncertainty	−0.794	0.679	1.37	0.2423
QJ[3/2]	0.460	0.789	0.34	0.5602
QJ[4/3]	−1.86	1.19	2.43	0.1192
QJ[5/4]	2.97	1.65	3.25	0.0714
QK: medical spending	0.0000361	0.0000278	1.69	0.194
QL: subjective CVD risk	0.00658	0.0144	0.21	0.6484
QM: willingness to pay	−0.0000964	0.0000361	7.11	0.0077g
QN[2/1]: life satisfaction	5.78	1.46	15.54	>0.0001g
QN[3/2]	−1.49	0.660	5.1	0.0239f
QN[4/3]	−0.554	0.827	0.45	0.5023
QN[5/4]	2.04	1.45	1.98	0.1591
QO[1]: DM consciousness	3.35	1,715	0	0.9984
QO[2]	−10.9	3,431	0	0.9975
QP[2/1]: patient understanding	0.773	0.589	1.72	0.1895
QP[3/2]	0.466	1.13	0.17	0.6823
QQ[1]: family understanding	3.49	597	0	0.9953
QQ[2]	5.36	597	0	0.9928
QQ[3]	3.60	597	0	0.9952

Notes:

a Whole model test: degrees of freedom 31, likelihood-ratio χ² test 82.79, and P-value <0.0001.

b Levels of diabetic retinopathy: 0 NDR, 1 SDR, 2 PPDR, and 3 PDR/PRP.

c HbA_1c at the time of survey.

d Survey questionnaires are shown in Table 1.

e Wald test for effects.

f P<0.05, significant by effect likelihood-ratio test.

g P<0.01, significant by effect likelihood-ratio test.

Abbreviations: BMI, body mass index; CVD, cardiovascular disease; DM, diabetes mellitus; HbA_1c, hemoglobin A_1c; NDR, no diabetic retinopathy; SDR, simple diabetic retinopathy; PPDR, preproliferative diabetic retinopathy; PDR/PRP, proliferative diabetic retinopathy including panretinal photocoagulation.

Table 5 Nominal logistic regression analysisa of factors associated with nephropathyb

Parameter	Estimate	Standard error	Chi-square test	P-valuee
Type (type 1)	−0.294	0.391	0.57	0.4516
Sex (male)	0.681	0.357	3.63	0.0567
Age	0.0880	0.0305	8.28	0.004g
Diabetes duration	0.0341	0.0378	0.81	0.3676
HbA1cc	−0.00612	0.270	0	0.9819
BMI	0.234	0.0966	5.9	0.0152f
Survey responsesd
QA: general risk proneness 1	0.00103	0.0150	0	0.9453
QB: general risk proneness 2	−0.00782	0.0232	0.11	0.7369
QC[1]: procrastination 1	−0.0149	0.624	0	0.9809
QC[2]	−0.865	0.647	1.78	0.1816
QE: lottery 1 low risk, low gain	0.0000761	0.0000335	5.15	0.0233f
QG: endowment effect	−0.0000211	0.0000126	2.78	0.0957
QH: myopic time preference 1	0.00000562	0.0000207	0.07	0.7867
QJ[2/1]: accept uncertainty	−1.15	0.743	2.41	0.1205
QJ[3/2]	0.316	0.924	0.12	0.7322
QJ[4/3]	0.590	1.18	0.25	0.6182
QJ[5/4]	−1.42	1.82	0.61	0.4331
QK: medical spending	−0.0000655	0.0000418	2.46	0.1171
QL: subjective CVD risk	0.0100	0.0158	0.4	0.5266
QM: willingness to pay	−0.0000370	0.0000302	1.5	0.2207
QN[2/1]: life satisfaction	2.63	1.38	3.62	0.0569
QN[3/2]	0.0289	0.723	0	0.9681
QN[4/3]	−0.0579	0.976	0	0.9527
QN[5/4]	−1.22	2.40	0.26	0.612
QO[1]: DM consciousness	−0.196	140,002	0	1
QO[2]	−25.0	221,361	0	0.9999
QP[2/1]: patient understanding	−0.633	0.610	1.08	0.2992
QP[3/2]	2.33	1.40	2.77	0.0963
QQ[1]: family understanding	−0.348	0.689	0.25	0.6138
QQ[2]	1.40	0.786	3.2	0.0737
QQ[3]	−1.39	0.730	3.66	0.0558

Notes:

a Whole model test: degrees of freedom 31, likelihood-ratio χ² test 59.22, P-value 0.0017.

b Nephropathy was defined as urinary albumin excretion ≥30 mg/g creatinine.

c HbA_1c at the time of survey.

d Survey questionnaires are shown in Table 1.

e Wald test for effects.

f P<0.05, significant by effect likelihood ratio test.

g P<0.01, significant by effect likelihood ratio test.

Abbreviations: BMI, body mass index; CVD, cardiovascular disease; DM, diabetes mellitus; HbA_1c, hemoglobin A_1c.

Figure 1 Box plot of responses to question QE showing quartiles and outliers.

Notes: QE, lottery 1 low risk, low gain. Type 1, 5,823±2,138 (mean ± SE); type 2, 5,064±8,347; difference of the means, Mann–Whitney U-test, P=0.2805; and difference of variances, standard F-test, P<0.0001.
Abbreviation: SE, standard error.

Table 6 Attitude to risk assessed by responses to a hypothetical lottery estimation (QE and QF)a

Attitude to risk	Type 1 diabetes				Type 2 diabetes
	Male		Female		Male		Female
	Risk averse	Risk seeking or no answerb	Risk averse	Risk seeking or no answer	Risk averse	Risk seeking or no answer	Risk averse	Risk seeking or no answer
Mean response to QE (JPY) (SD)	472 (397)	10,300 (15,195)	578 (349)	10,970 (23,308)	641 (344)	7,313 (11,885)	512 (422)	5,924 (4,846)
Mean response to QF (JPY) (SD)	690 (72)	5,800 (637)	657 (377)	12,466 (25,385)	735 (351)	8,565 (16,427)	437 (370)	7,268 (11,880)
Mean age (SD)	52.6 (12.8)	52.1 (15.0)	43.3 (13.7)	49.5 (12.9)	63.9 (10.3)	61.6 (10.8)	54.1 (23.2)	62.1 (10.8)
Patients number by age
Under 45	3	4	10	10	1	4	4	1
45–under 65	6	5	3	7	6	25	0	19
65 or older	2	4	1	3	10	19	4	17
Total patients number (% in the sex)	11c (45.8%)	13 (54.2%)	14c (41.2%)	20 (58.8%)	17 (26.2%)	48 (73.8%)	8 (17.8%)	37 (82.2%)

Notes: QE, lottery 1 low risk, low gain; QF, lottery 2 high risk, high gain.

a Questionnaires QE and QF are shown in Table 1.

b Risk seeking or no answer includes the zero-answers.

c Prevalence of risk averse category was higher in patients with type 1 diabetes compared with patients with type 2 diabetes (P<0.05).

Abbreviation: SD,standard deviation.