The art of measuring the quality of life

Quality of life measurements are often included in health economics analyses. However different methods can yield varying results, thereby influencing decisions on whether a treatment is to be implemented in healthcare or not, as shown in a doctoral thesis at Linköping University.

Many people with diabetes suffer from vision loss, or diabetic retinopathy. It’s a complication in the retina of the eye that starts with blurry spots in the field of vision, and in worst cases leads to blindness. The longer someone has had diabetes, the worse the problem becomes.

“We were interested in how patients with this complication were coping, and the cost to society,” says Emelie Heintz, graduate student in health economics, who defended her thesis May 4.

The thesis is built in part on a registry study of 12,026 patients diagnosed with diabetes in Östergötland, East Sweden, between 2001 and 2007, and in part on interviews with 167 people regarding their quality of life.

The illness is found in four out of ten people with Type 1 diabetes and in three out of ten people with Type 2 diabetes, which indicates that fewer today are afflicted as compared with 10-20 years ago. The healthcare costs for this eye complication alone are estimated at SEK 100 million per year, but a larger amount appears to exist outside of healthcare, covering such things as informal care provided by close relatives. With this included, the total comes to around SEK 400 million per year, a number that could be compared with earlier valuations of the total cost for all diabetes: SEK 8 billion.

Patients whose vision deteriorated as a consequence of their diabetes, not unexpectedly, turned out to have a lower quality of life owing to problems with reading, for example, recognizing acquaintances from a distance, and moving about unhindered. They also felt increased anxiety and worry.

“We expected that many would be worried about the diagnosis itself. But the big difference in quality of life didn’t emerge until they started seeing poorly,” says Heintz (pictured).

In the interviews, she used four different methods of measuring quality of life.

“It’s important to study how well the various instruments capture the effects of the illness, since the results are used for things like decisions on which treatments are to be included in Swedish protection against high costs for medicine,” Heintz says. It’s therefore interesting that you can get differing results depending on which instrument is used.

In one often-used method, the patient is requested to imagine living with their current state of health for a certain time, usually ten years or the statistically expected remaining length of life. Then they answer the question: How many years are you willing to give up against being able to live completely healthy for the rest of your life? The more someone is prepared to barter, the worse they experience their quality of life.

The method – “time trade-off” – has weaknesses, however, that could lead to distorted evaluations if the patients’ own expectations of their length of life differ from the questioner’s.

“If I gave them 40 years in the exercise and they believed they’d only live 35, they were ready to barter a greater number of years. If you don’t take that into consideration, you risk inaccurate results, which in turn can lead to an incorrect distribution of health care resources,” Heintz says.

Thesis: Health economic aspects of diabetes retinopathy by Emelie Heintz (Linköping University medical dissertations No. 1293) presented on Friday, May 4, 2012 at 9:00 AM in Eken, Hospital Campus, Linköping. The examiner was Professor Josephine Mauskopf, Duke University, USA.

Contact: Emelie Heintz +46 709-567569

 

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Related Links

• Emelie Heintz 
• The Center for Medical Technology Assessment (CMT) at Linköping University

Åke Hjelm 2012-05-02