Eliciting health state utilities in Japanese diabetic and obese patients through the time trade-off method. Does the conjecture fat and happy stand true?

This article is related to:

Health state utilities associated with weight loss in type 2 diabetes and obesity

Introduction

Since the beginning of human existence, peoples’ perceptions of the ideal body type have massively oscillated. Venus, goddess of love, was depicted as curvy and voluptuous, a testament to her association with love and fertility and her visualization, as in the Venous de Milos statue, is a stark contrast to the twenty-first century dominant pattern of female appearance, which mandates slim-waisted body types.

Therefore, the uncertainty engulfing the ideal body has also permeated to the relationship between body weight and individual’s satisfaction. Despite that some anecdotal evidence suggest a positive relationship between body mass index ( BMI) and happiness, which have further fueled the movement “my body, my choice” coined by pro-choice activists to represent freedom of choice and bodily autonomy, a string of scientific publications underline a negative effect between happiness and BMI^1,2. More importantly, a substantial body of evidence demonstrated a causality effect between increased body weight and risk for diabetes, cardiovascular events and musculoskeletal conditions³.

A magnitude of pharmaceutical modalities aiming to help individuals lose weight were brought into market, however their mediocre potency, coupled with serious adverse events plummeted their further uptake and waned public interest as attested by Onakpoya who studied products launched between 1944 and 2006 and were withdrawn from the market between 1964 and 2009⁴.

As a new class of category of antidiabetic agents emerges, the glucagon-like peptide-1 agonists, we observe a revamped interest in pharmaceutical weight loss interventions, which has even backlashed to shortages of these agents, that poses a threat to diabetic patients⁵. Consequently, the relationship of health utilities and BMI has been thrust into the limelight. Moreover, the elicitation of health utilities in diabetic patients, is of utmost importance in the cost-utility analysis. Cost-utility analysis (CUA) comprises a decisive tool in the reimbursement process of new medicines, and its importance steps up substantially in high volume and value modalities, which aligns perfectly with the characteristics of antidiabetic agents’ market. CUA has been established as a pre-requisite in the reimbursement pathway in many countries, therefore the need for sound CUA is overarching.

So far, the body of evidence has assessed the relationship of health utilities with a modest weight loss up to 7%. Given that for diabetic patients, higher weight loss is required and anticipated, a study hailing from UK cast light to the utility gains associated with weight decreases of up to 20% of one’s body weight⁶.

The extrapolation of these findings from UK to other regions and specifically continents, is hindered owing to culture reasons, diverging perceptions of body and definitely the average BMI. Despite that in Boyle’s et al. UK study, 48.5% of participants had BMI 25–29 kg/m², the obesity BMI threshold higher in UK (BMI 30 kg/m²) than in Japan (BMI 25 kg/m²).

Consequently, this gap regarding utility and BMI in patients with T2D hailing from Japan should ideally be filled by a new study.

New data

In the current issue of JEM, Matza et al. reported their time trade-off (TTO) utility elicitation study which was performed with vignette-based methods in 138 obese individuals with type 2 diabetes (T2D) in Japan⁷. Eligible participants had a BMI cutoff of 25 kg/m², which is the commonly accepted threshold for obesity in Japan. The study consisted of eight health states (current weight and reductions of 2.5%, 5%, 7.5% 10%, 12.5% 15%, and 20% respectively) and the mean utility change was calculated for each of the seven reduction states. Each health state comprised two sections of “Type 2 Diabetes” and “Weight”. Then a description of T2D was delineated, accompanied by a description of body weight, with all the increments leading to 20% reduction of current weight.

The weight reduction health states included one bullet with the current weight and then the corresponding weight percentage reduction (2.5%, 5%, 7.5%, 10%, 12.5%, 15%, or 20%).

The TTO provided that participants were given the option to spend a 20-year period in each health state or different lengths of time in full health for each health state. Options were shown in steps of one year, with larger and shorter time periods (e.g. 20 years, 0 years [dead], 19 years, 1 year, etc.) alternated. The point of indifference between the years in the health state being valued (y) and the years in full health (x) was used to award utility ratings (u), where u = x/y.

The self-administered, preference-based with five dimensions (mobility, self-care, regular activities, pain/discomfort, and anxiety/depression) EQ-5D-5L was used to assess the sample’s general state of health. Each dimension has five response options that respondents choose from.

Responders reported an average desired weight loss of 9.9 kg and the mean EQ-5D-5L index score was highest for the lowest BMI group (0.913) and lowest for the highest BMI group (0.882).

Of interest is the fact that the majority of the participants (81.9%) ranked their current weight health state as their least desired health state. However, a wide variety of preferences were found for the health condition that represented the greatest percentage of weight reduction (20%). Of the participants, 75 (54.3%) rated this health state as the most favored, while 25 (18.1%) assessed this as the least preferred. When compared to the remaining 63 participants in the sample, the 75 persons who evaluated this health condition as most favored had a substantially higher BMI (31.2 kg/m² vs. 27.3 kg/m²; p < 0.001).

The 20% weight reduction was ranked as the most desirable by participants, who also stated that they wanted to be "as light as possible" or that their ideal weight was close to or below the 20% drop. Nevertheless it was also postulated that the aforementioned reduction was generally viewed as excessive by those expressed concerns pertinent to potential impairment of their health, strength or energy by this weight loss.

Health state utilities

At least one of the weight reduction health states was chosen by all participants over their current weight.

The mean health state utilities indicated that respondents preferred to lose weight. The mean utilities of all the health states that represented weight reduction - 2.5% to 15% of current weight - were higher than the mean utilities of the respondent’s own current weight (current weight). Utility was inversely correlated with weight for weight reductions up to 15%; lower body weight was associated with a steady improvement in utility. All comparisons between mean utility of each weight reduction health condition and the mean utility of the present weight health state were statistically significant.

The health condition with the respondents’ present weight had mean utilities of 0.783, while the 15% weight reduction culminated to higher mean utilities of 0.830. The utility gains linked to weight loss varied, starting at 0.013 for a 2.5% weight loss and reaching 0.048 for a 15% weight loss. There was no discernible difference between the utilities of the health states with 15% and 20% weight reduction (0.830 vs 0.827) with the mean utility of the 20% weight reduction health state estimated marginally lower than the corresponding one of the 15% weight reduction health state. Factors such as age, gender, employment position, BMI, or medication currently used, did not confound results.

Overall, this study reiterates the UK findings and indicate that in Japanese Diabetic and obese patients, weight loss was linked to improvements in utility. Utility gains were positively correlated with the proportion of weight lost increased. A wide variety of preferences were elucidated for the 20% weight reduction health state, even though all individuals favored health states with lower weights over this one compared to their current weight. For 75 participants (54.3%), this was the most desired health condition; nevertheless, for 25 people (18.1%), it was the least desired. The mean BMI of those who favored larger percentages of weight reduction was significantly higher than that of those who chose the health condition of 20% weight reduction as their top choice. In other words, individuals who had lower BMIs were less inclined to favor losing the most weight. Notably, utilities did not differ statistically significant by BMI subgroups (i.e. BMI above and below 30 kg/m²).

In conclusion, this study offers estimates of the utility change linked to weight loss among Japanese adults with type 2 diabetes and obesity. The findings of this study may be used as a stepping stone for cost-utility studies in Japan and other countries in Asia in the field of diabetes.

Transparency

Acknowledgements

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Declaration of financial/other relationships

No potential conflict of interest was reported by the author.

Additional information

Funding

No funding was received to produce this article.