Risk Preferences, Rationality of Choices, and Willingness to Pay for Preventive Medicine in Patients with Graves’ Thyrotoxicosis

Figures & data

Table 1 Clinical Characteristics of the Participants

	Group A	Group B	p value
Thyroid Status at Initial Survey Recruitment	Hyperthyroid	Euthyroid
n (male:female)	86 (16:70)	33 (3:30)
Treatment duration	Within 1 month	1–20 years	< 0.001
Age (y)	47.2 ± 14.2	51.7 ± 16.8	0.184
TSH (µIU/mL) (0.35–4.94)^a	< 0.001	1.69 ± 1.16	< 0.001
FT3 (pg/mL) (1.71–3.71)^a	5.73 ± 4.48	2.52 ± 0.31	< 0.001
FT4 (ng/dL) (0.70–1.48)^a	1.76 ± 0.83	0.95 ± 0.12	< 0.001
First survey returned, n (%)	65 (76)	28 (85)	0.260
Second survey recruitment n (male:female)	54 (10:44)	11 (1:10)	0.419
Second survey returned, n (%)	36 (67)	11 (100)	0.005

Notes: Age and serum levels of TSH, FT3, and FT4 are presented as mean ± standard deviation. ^aReference range.

Table 2 Paired Analysis of Differences Between the First and the Second Survey in Group A Patients (Hyperthyroid at the First Survey and Euthyroid at the Second Survey)

Variable	First	Second	t or Chi-Square	p value
Age (y)	46.0 ± 14.2	46.7 ± 14.2
Survey returned,^a n (%)	39 (75)	36 (69)	0.818	0.366
Body mass index (kg/m^2)	21.5 ± 3.1	22.1 ± 3.0	4.77	< 0.001
TSH (µIU/mL) (0.35–4.94)^b	< 0.001^d	1.85 ± 1.28	10.4	< 0.001
FT3 (pg/mL) (1.71–3.71)^b	6.03 ± 4.76	2.39 ± 0.31	–5.50	< 0.001
FT4 (ng/dL) (0.70–1.48)^b	1.79 ± 0.86	0.92 ± 0.15	–6.83	< 0.001
Q1 General risk loving, weather	50.5 ± 21.6	50.3 ± 19.5	–0.425	0.681
Q2 General risk averse, travel	22.9 ± 11.0	20.8 ± 9.2	–1.02	0.317
Q3 Feeling rushed^c	2.60 ± 1.10	2.50 ± 1.20	–0.205	0.839
Q4 Sleeping hours	6.29 ± 1.04	6.25 ± 1.00	–0.636	0.530
Q5 Sleep deprivation^c	3.10 ± 1.19	3.14 ± 1.22	0.279	0.782
Q6 Procrastination, childhood^a Early:Daily:End, n (%)	5:8:26 (13:21:67)	8:8:20 (22:22:56)	2.00	0.572
Q7 Procrastination, now^a Early:Daily:End, n (%)	22:9:8 (58:23:21)	19:10:7 (53:28:19)	1.20	0.753
Q8 Acceptance of medical uncertainty^c	2.10 ± 0.94	1.94 ± 0.83	–1.36	0.184
Q9 OOPmed (¥/month)	8141 ± 6094	6012 ± 3726	–1.99	0.056
Q10 Subjective risk estimation for CVD (people/100)	30.7 ± 25.1	34.2 ± 23.0	0.781	0.441
Q11 WTPcvr (¥/month)	8929 ± 16,378	7000 ± 9789	–1.33	0.194
Q12 Lottery, risk taker, maximum price (¥)	1327 ± 215	1286 ± 221	–0.576	0.569
Q12 Irrational response, n (%)^a	5 (12.8)	5 (13.9)	0.333	0.564
Q13 Insurance, risk averse, maximum price (¥)	2810 ± 2432	4473 ± 8536	1.19	0.245
Q13 Irrational response, n (%)^a	5 (12.8)	4 (11.1)	0.000	1.000

Notes: A total of 32 paired samples were analyzed. Data are presented as the number, %, or mean ± standard deviation. Paired t-tests were performed for continuous variables. ^aFor nominal scales, McNemar–Bowker tests were applied using chi-square test. ^bReference range. ^cOrdinal scales were treated as continuous variables. ^dTSH < 0.001 (µIU/mL) was calculated as zero.

Abbreviations: OOPmed, out-of-pocket average monthly expenditure on medical care; CVD, cardiovascular disease; WTPcvr, willingness-to-pay for a medicine that could reduce CVD risk.

Table 3 Single Regression Analysis of Survey Items Using Serum Level of FT3 as an Independent Variable

Dependent Variable	n, %, or Mean ± SD	Estimate	Standard Error	t Ratio or Chi-Square	p value
Surveys returned,^a,b n (%)	140 (76)	–0.064	0.063	1.01	0.315
Q1 General risk loving, weather	50.8±20.3	0.716	0.470	1.52	0.130
Q2 General risk averse, travel	20.9±11.0	–0.015	0.258	–0.060	0.954
Q3 Feeling rushed^c	2.60±1.20	0.013	0.029	0.740	0.642
Q4 Sleeping hours	6.22±1.08	–0.011	0.025	–0.420	0.676
Q5 Sleep deprivation^c	3.01±1.22	–0.019	0.029	–0.670	0.501
Q6 Procrastination, childhood^b Early:Daily:End, n (%)	26:31:83 (19:22:59)
Early vs End		–0.058	0.070	0.690	0.407
Daily vs End		–0.237	0.131	3.24	0.072
Q7 Procrastination, now^b Early:Daily:End, n (%)	80:31:29 (57:22:21)
Early vs End		–0.034	0.058	0.440	0.509
Daily vs End		0.007	0.063	0.010	0.906
Q8 Acceptance of medical uncertainty^c	2.06±0.88	–0.013	0.020	–0.660	0.510
Q9 OOPmed (¥/month)	7189±6271	385	143	2.70	0.008
Q10 Subjective risk estimation for CVD (people/100)	31.1±22.4	–0.624	0.522	–1.20	0.234
Q11 WTPcvr (¥/month)	7306±11,436	741	261	2.84	0.005
Q12 Lottery, risk taker, maximum price (¥)	1095±1474	24.6	34.4	0.710	0.476
Q12 Irrational response, n (%)^b	20 (14.3)	–0.009	0.069	0.020	0.895
Q13 Insurance, risk averse, maximum price (¥)	4061±7512	4.53	176	0.030	0.980
Q13 Irrational response, n (%)^b	20 (14.3)	–0.029	0.076	0.150	0.6945

Notes: A total of 140 surveys (combined first and second surveys of groups A and B) obtained from 119 patients were analyzed. ^aSurvey return rate was analyzed as the serum FT3 levels obtained at recruitment. ^bFor the nominal scales, logistic regression analysis was performed with chi-square test. ^cOrdinal scales were treated as continuous variables.

Abbreviations: OOPmed, out-of-pocket average monthly expenditure on medical care; CVD, cardiovascular disease; WTPcvr, willingness-to-pay for a medicine that could reduce CVD risk.

Figure 1 Linear fit of prices willing to pay for reducing CVD risk (Q11) according to serum level of FT3. Of the 140 returned survey forms from a cumulative total of 184 surveys given to 119 patients, 7 surveys in 6 patients did not have answers for Q11. A total of 133 answers in 113 patients were analyzed. Price willing to pay (¥/month) = 4219 + 741 × FT3 (pg/mL), R² = 0.0580. Analysis of variance; degree of freedom = 1, sum of square = 1,000,897,112, F Ratio = 8.06, p = 0.0052.

Figure 2 Linear fit of average out-of-pocket expenditure on medical care (Q9) according to serum level of FT3. Of the 140 returned survey forms from a cumulative total 184 surveys given to 119 patients, Q9 was not answered in two surveys. A total of 138 answers in 117 patients were analyzed. Out-of-pocket expenditure (¥/month) = 5599 + 385 × FT3 (pg/mL), R² = 0.0508. Analysis of variance; degree of freedom = 1, sum of square = 273,587,993, F Ratio = 7.28, p = 0.0079.

Figure 3 Linear fit of prices willing to pay for reducing CVD risk (Q11) according to average out-of-pocket expenditure on medical care (Q9). A total of 131 answers in 111 patients were analyzed. Price willing to pay (¥/month) = 3484 + 0.540 × out-of-pocket expenditure (¥/month), R² = 0.0840. Analysis of variance; degree of freedom = 1, sum of square = 1,448,079,694, F Ratio = 11.84, p = 0.0008.

Table 4 Multiple Regression Analysis of Factors Associated with Price Willingness-to-Pay for a Medicine Reducing CVD Risk (WTPcvr) (Q11)

Independent Variable	Estimate	Standard Error	t Ratio	p value	VIF
Age (y)	24.6	68.0	0.360	0.718	1.02
FT3 (pg/mL)	533	263	2.03	0.044	1.06
Q9 OOPmed (¥/month)	0.435	0.160	2.72	0.008	1.08
Q10 Subjective risk estimation for CVD (people/100)	–81.8	42.6	–1.92	0.057	1.02
Q17 Economic status^a	–162	1141	–0.140	0.887	1.02

Notes: A total of 140 surveys obtained from 119 patients were analyzed. ^aOrdinal scale was treated as a continuous variable.

Abbreviations: OOPmed, out-of-pocket average monthly expenditure on medical care; CVD, cardiovascular disease; VIF, variance inflation factor.