Generalized Estimating Equations (GEE) to handle missing data and time-dependent variables in longitudinal studies: an application to assess the evolution of Health Related Quality of Life in coronary patients.
OBJECTIVE
to analyse the evolution of Health Related Quality of Life (HRQL) in coronary patients (CP) and to identify predictive factors influencing this evolution in a situation with missing data and time-dependent variables.


METHODS
prospective study with repeated measures.


METHODS
a total of 175 CP were included. General Estimating Equations (GEE) models were used to assess the evolution of HRQL in these patients. These models, not commonly used in this context, are applied here as an alternative to traditional techniques that do not handle missing data and time-dependent covariates properly.


METHODS
HRQL assessed by SF-36v1 Questionnaire at baseline, 3 and 6 months after discharge.


RESULTS
role physical, bodily pain, general health, vitality, and the physical component summary of SF-36 improved over the follow-up. Being woman, older, and having higher scores on GHQ-28 were associated to a decrease in HRQL throughout time. Previous history of coronary heart disease, comorbidities, revascularisation, rehospitalisation, and episode of angina had a negative impact on HRQL, especially between 3 and 6 months after discharge.


CONCLUSIONS
the analysis of the evolution of HRQL with a longitudinal approach using GEE models shows the predictive effect of the variables analysed during the follow-up, including the time itself and time-dependent covariates such as the evolution of mental health. In addition, it allows to particularise the predictive effect of covariates at each period within the follow-up.
Salus Infirmorum Faculty of Nursing, University of Cádiz, Spain.
Marìa
M
Duenas
Preventive Medicine and Public Health Area, University of Cádiz, Spain. alejandro.salazar@uca.es.
Alejandro
A
Salazar
Preventive Medicine and Public Health Area, University of Cádiz, Spain.
Begona
B
Ojeda
Cardiology Department, University Hospital Puerta del Mar Cádiz, Spain.
Roque
R
Arana
Preventive Medicine and Public Health Area, University of Cádiz, Spain.
Inmaculada
I
Failde
D017677:Age Distribution; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology*; D005500:Follow-Up Studies; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008137:Longitudinal Studies; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011788:Quality of Life; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D011795:Surveys and Questionnaires