Multiple illness perceptions in older adults: effects on physical functioning and medication adherence.
OBJECTIVE
Previous research on illness perceptions has focused on single illnesses, but most adults over 65 suffer from multiple illnesses (multimorbidity). This study tests three competing operationalisations of multiple illness perceptions in predicting physical functioning and adherence: (1) main effects and interactions model; (2) peak model with effects of the most prominent illness perception; and (3) combined model with averaged illness perceptions over multiple illnesses.


METHODS
Longitudinal study in N = 215 individuals (65-86 years) with multimorbidity at two measurement points over six months. Participants filled in two Brief Illness Perception Questionnaires (B-IPQ) on their two most severe illnesses.


METHODS
Physical functioning, medication adherence.


RESULTS
Factor analyses suggest that the B-IPQ contains three dimensions; consequences, control and timeline. Multiple regression models fit the data best for (1) and (3). Timeline (β = -.18) and control (β = .21) predict adherence in (1); consequences (β = .16) and control (β = .20) in (3). Physical functioning was significantly predicted by interacting control beliefs in (1; β = .13), by peak consequences in (2; β = -.14) and by consequences (β = -.15) in (3).


CONCLUSIONS
Individuals with multimorbidity hold both distinct and combined perceptions about their illnesses. To understand individual responses to multimorbidity, perceptions about all illnesses and multimorbidity as entity should be examined.
a School of Psychology , University of Tasmania , Hobart , Australia.
Benjamin
B
Schüz
Julia K
JK
Wolff
Lisa M
LM
Warner
Jochen P
JP
Ziegelmann
Susanne
S
Wurm
D000203:Activities of Daily Living / Q000523:psychology*; D000368:Aged; D000369:Aged, 80 and over; D001294:Attitude to Health; D015897:Comorbidity; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D055118:Medication Adherence / Q000523:psychology*; D011795:Surveys and Questionnaires; D016903:Drug Monitoring