Original Article
In an exploratory prospective study on multimorbidity general and disease-related susceptibility could be distinguished

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Abstract

Objectives

To further disentangle multimorbidity and its relation with psychosocial characteristics, by categorizing combinations of diseases within a patient as general or disease-related susceptibility, based on the presence or absence of a pathophysiological communality of diseases.

Study Design and Setting

A cohort of 3,460 patients that previously took part in a study on multimorbidity was followed up for a period of 2 years. Context: the Registration Network Family Practices, which is a continuous and computerized database in Dutch general practice that covered over 60,000 patients at the time of the study.

Results

During 2-year follow-up 91.6% did not show susceptibility, 4.2% showed general susceptibility, 1.4% disease-related susceptibility, 0.8% both general and disease-related susceptibility, and 1.9% patients could not be classified. None of the studied characteristics was significantly related to the occurrence of disease-related susceptibility. A decreased risk for general disease susceptibility related to an internal health locus of control, an active and palliative coping style, and the occurrence of positive life events.

Conclusion

The distinction between general susceptibility and disease-related susceptibility is feasible and seems useful. Further development of this methodology is needed, as is confirmation of these results in a larger study population.

Introduction

Multimorbidity, the co-occurrence of diseases, is frequent and burdens the patient, family members, and society as a whole. Previous research shows that a significant proportion of people suffer from various diseases, varying from 29.7% in the general Dutch population [1] to over 50% in Americans aged 60 years and older [2]. Until now most medical research (etiologic, as well as diagnostic and therapeutic) has focused on single diseases or specific combinations of diseases. This has resulted in better understanding of health and disease and subsequently in better health care. However, taking into account this body of knowledge, it is not understood why many patients get one disease after another, whereas others are hardly ever diseased [3]. So far, there is no satisfying explanation for obvious differences in disease susceptibility [4]. However, research into biological, behavioral, psychological, and demographic factors and their relation to health status has led to the theory of general disease susceptibility [5]. This theory states that sociological, psychological, genetic, and immunological factors are underlying factors that influence susceptibility to a wide range of diseases. They are general rather than specific risk factors.

Previous studies comparing subjects with multimorbidity and subjects without multimorbidity with regard to sociological and psychological features revealed that multimorbidity is related to health locus of control, coping style, size of the social network, and life events [6], [7]. These relations were weak but consistent, hence indicating the relevance of both the concept of disease susceptibility and its relation with sociological and psychological features.

Until now, research on co-occurrence of diseases has had important methodological limitations [8]: previous studies either used a small number of diseases (maximum of 13 diseases included in the analysis) [2] or used a very broad definition (two or more co-occurring serious diseases) [1]. If the above definitions are used as an indicator of general disease susceptibility this, respectively, may lead to underestimation (resulting from the limited number of diseases included in the analysis) and overestimation (whereas all diagnoses, including obvious complications, are counted) of the occurrence of clinically relevant multimorbidity. From this point of view it seems valid to adjust disease susceptibility for known pathophysiological relations. Specification, by taking into account known pathophysiological relations, will yield more typical disease entities, and hence more typical multimorbidity profiles and more powerful relations with psychosocial characteristics.

In this study we aim to further disentangle multimorbidity and its relation with a number of psychosocial patient characteristics. To achieve this all combinations of diseases within a patient will be categorized as so-called “general disease susceptibility” or so-called “disease-related susceptibility.” This distinction will be based on the presence or absence of a pathophysiological communality of diseases. This study is a first attempt to evaluate the feasibility and relevance of such a distinction.

Both the general susceptibility and disease-related susceptibility will then be evaluated in terms of associations with psychosocial features through a comparison with subjects who showed no disease susceptibility.

Section snippets

Population

For this study data were available on 3,460 subjects who took part in a study on the association between patient characteristics and the occurrence multimorbidity (i.e., multiple pathology) in a time-window of 2 years. This study was carried out within the context of the Registration Network Family Practices (RegistratieNet Huisartspraktijken; RNH) [9]. This is a continuous and computerized database in general practice that covered over 60,000 patients at the time of the study. All relevant

Population

Table 1 shows the background characteristics of the population, which consisted of 1,737 males (50.2%) and 1,723 females. The mean age of our population was 52.4 years (standard deviation 16.8). Over one fifth did not have any disease at the start of this study, a comparable number had one disease, and slightly over half of the population had two or more diseases at the start.

During follow-up the majority (91.6%) did not show susceptibility (74.2% no new diseases and 17.4% one new disease). Of

Discussion and conclusion

This article describes the results of a first exploration of the relevance and feasibility to distinguish between general disease susceptibility and disease-related susceptibility and to relate both general disease susceptibility and disease-related susceptibility to psychosocial characteristics. It was hypothesized that taking into account the known (pathophysiological) relations between diseases count leads to a clearer psychosocial profile in relation to disease susceptibility.

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