2What Is Quality of Life, and How Do You Put a Number on It?
Quality of life sounds too soft to measure, yet health economics turns it into a single number between 0 and 1. This module explains what health-related quality of life means, how a health state is converted into a utility where 0 is death and 1 is perfect health, and how that number becomes the raw material a QALY needs. Along the way we meet the three classic ways patients are asked to value a health state, and the difference between generic and disease-specific measurement.
FFrom feeling to figure: what health-related quality of life means
Health-related quality of life (HRQoL) is the part of overall wellbeing that depends on health: physical function, emotional state, social participation and communication, rather than wealth or environment alone. To use HRQoL in economics it is collapsed onto a single health-utility scale anchored at 0 (death) and 1.0 (perfect health), so health states can be both ranked and assigned a cardinal value. A conceptual model links biological and physiological variables to symptom status, then functional status, then HRQoL and overall quality of life, with personality and social or economic supports modifying each step. Profound hearing loss in adulthood carries a measured utility decrement of roughly -0.46 on the 0-to-1 scale, comparable to other chronic conditions.[1995][1986][1996]
FEliciting a utility: VAS, time trade-off, and standard gamble
The visual analogue scale (VAS) has the respondent mark the state on a worst-to-best line; easy to obtain but not a true preference-based value. The time trade-off (TTO) asks how many years of impaired life a person would give up for a shorter time in perfect health; the ratio of years yields the utility. The standard gamble (SG) chooses between certain impaired health and a gamble at perfect health carrying a death risk; the indifference probability is the utility. In CI studies Summerfield VAS gains were about +0.23 to +0.41, while Palmer's prospective HUI comparison showed roughly +0.20 over one year.[1989][1995][1999]
FGeneric versus disease-specific: two ways to capture hearing
The Health Utilities Index Mark III scores eight attributes including a dedicated hearing and speech item; the EQ-5D covers five dimensions valued with population tariffs. Generic measures allow comparison with cardiac or orthopaedic surgery but concentrate their sensitivity to deafness in non-hearing domains, so they can underestimate hearing benefit. The CIQOL suite (CIQOL-35 Profile and CIQOL-10 Global) covers six implant-relevant domains and detects implant gains more reliably than legacy generic tools. Only generic preference-based scores feed a QALY directly; disease-specific scores describe the lived hearing experience but must be bridged to utility first.[1996][2001][2019]
FThe bridge to a QALY
A quality-adjusted life year is life expectancy multiplied by the health-utility score, so a year lived at 0.5 counts as half a QALY. Worked example: 20 years lived at a utility of 0.2 generates 20 times 0.2 equals 4 QALYs. An implant raises adult utility by a pooled average of about +0.26 (95% CI +0.24 to +0.28), crediting roughly a quarter of a QALY per year of use. Those gains later produce cost-utility ratios such as the pooled adult figure near $12,847 per QALY, but only after quality of life is pinned to a single 0-to-1 number.[1986][2009][1999]
On the scale used to express his score of 0.50, what do the anchors 0 and 1.0 represent, and what does 0.50 imply?
A patient is expected to live 20 more years at a constant health utility of 0.2. How many QALYs is that, and why?
Which best contrasts a generic preference-based instrument (HUI3, EQ-5D) with a disease-specific one (CIQOL) in CI evaluation?