Table 2 Synthesis of studies on multimorbidity with quality of life as the main outcome measure

Cheng 2003 [36] (United States)

Cross-sectional design

Ambulatory, family medicine.

n = 316 (55–64 years)

7 diagnoses of chronic conditions obtained by chart review.

Medical Outcomes Study (SF-36).

Administered by interviewer.

Definition of multimorbidity was based on simple count of diseases. No assessment of disease severity or use of a healthy group for comparison.

No mention of psychiatric comorbidity.

Limited to low-income population. Small sample.

Age of the sample was limited.

For every SF-36 domain, scores obtained in pregeriatric patients are significantly lower than those obtained in the general population. Lower physical component summary scores (PCS) and mental component summary scores (MCS) are associated with a greater number of chronic diseases, but this association is much stronger for PCS than MCS.

Wensing 2001 [37] (Netherlands)

Cross-sectional design

Ambulatory, family medicine.

n = 4,112 (18+ years)

25 diagnoses of chronic conditions, with the possibility of including other diagnoses reported spontaneously.

Self-administered questionnaire.

Medical Outcomes Study (SF-36); 8 domains.

Self-administered.

Definition of multimorbidity was based on simple count of diseases. Medical conditions were self-reported by patient, with no assessment of disease severity. Psychiatric comorbidity was not evaluated.

Prevalences of chronic conditions were abnormally low, consistent with a selection or information bias.

The QOL in each of the domains declines with the number of diagnoses (0, 1, 2 and over) but less so for the mental health domain.

The QOL score declines with age, especially in physical domains.

Michelson 2001 [38] (Sweden)

Cross-sectional design

General adult population, stratified according to age.

n = 3,069 (18–79 years)

13 diagnoses of chronic conditions, divided into 4 categories based on the number of problems: (0, 1–2, 3–4, 5+).

Self-administered questionnaire.

European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ); 5 domains.

Self-administered.

Too few diagnoses considered. Medical conditions were self-reported by patients, with no assessment of disease severity. Psychiatric comorbidity was not evaluated.

Although adequate for use as a generic measure, the QOL questionnaire was developed for cancer patients.

The presence of multiple chronic problems is associated with a lower QOL score. This association is present for each age group and tends to reduce the relationship between age and QOL.

The impact of socio-demographic and economic factors varies with age.

Cuijpers 1999 [39] (Nether-lands)

Cross-sectional design at the beginning of a cohort study

Residents of homes for the elderly. n = 211 (Mean = 84.3 years)

7 diagnoses of chronic conditions, with the possibility of including other diagnoses reported spontaneously.

Questionnaire administered by the nursing staff.

Short-Form-20 Health Survey (SF-20); 5 domains.

Administered by interviewer.

Too few diagnoses considered. No assessment of disease severity.

Psychiatric comorbidity was not evaluated.

Data collection procedure was not standardized.

Many refusals to participate (30%), including some for health reasons.

Small sample. Aged patients.

A lower QOL score is associated with a high number of chronic conditions.

Grimby and Svanborg 1997 [40] (Sweden)

Cross-sectional design in a cohort follow-up

General ambulatory. n = 565 (76 years)

16 diagnoses of chronic conditions present in > 5%.

Medical questionnaire.

Modified Nottingham Health Profile (NHP); part I: 6 dimensions; part II: 5 questions.

Self-administered.

Definition of multimorbidity was based on a simple count of diseases. No assessment of disease severity.

Health of nonrespondents was not comparable (more ill).

No age variation (76 years).

The loss of QOL is proportional to the number of diagnoses for the dimensions of energy, pain, mobility, and sleep. For social and emotional dimensions, QOL is little influenced until health is significantly impaired (4 or more diagnoses).

Kempen 1997 [41] (Nether-lands)

Cross-sectional design at the beginning of a cohort study

Ambulatory, family medicine. n = 5,279 (57+ years)

18 diagnoses of chronic conditions.

Questionnaire administered by interviewer.

Short-Form-20 Health Survey (SF-20); 6 domains.

Administered by interviewer or self-administered.

Definition of multimorbidity was based on simple count of diseases reported by the patient.

Use of a list of diagnoses in correlation and multiple regression analyses.

No assessment of disease severity or psychiatric comorbidity.

Age of the sample was limited.

The presence of chronic medical conditions explains a high proportion of the variance (25%) in the QOL score in most domains, especially self-perceived health. Personality influences QOL scores, especially in the mental health domain.

The association between the number of chronic conditions and the QOL score is slightly stronger for women than men.

Fryback 1993 [42] (United States)

Cross-sectional design

General ambulatory. n = 1,356 (45–89 years)

28 diagnoses of chronic conditions, with the possibility of including other diagnoses reported spontaneously.

Questionnaire administered by interviewer.

Medical Outcomes Study (SF-36) reduced to 2 domains.

Quality of Well-Being scale (QWB).

Administered by interviewer.

Definition of multimorbidity was based on a simple count of diseases reported by patient. No assessment of disease severity.

QOL questionnaire completed by the same interviewer immediately after the medical questionnaire.

Characteristics of the healthy group were not described.

Multimorbidity data were not adjusted for age.

Questionnaire did not include all domains traditionally included in QOL assessment.

The QOL score, as estimated with all of the measuring instruments, decreases with the number of chronic medical conditions. However, only limited domains of QOL were evaluated.