Summary
Over the course of 4.5 years, patients’ HRQoL significantly declined with increasing age, increasing walking impairment, and incident hearing impairment. A significant positive development was achieved through an increased physical activity score. These findings were modified by sex, education level, and depression; in females and in patients with a low education level in particular, increasing physical activity significantly improved HRQoL, whereas incident hearing impairment significantly decreased it. Moving to an institutional setting (care home or residential home) only strongly improved HRQoL in patients with a low education level and in those without depression.
Strengths and limitations
This is the first study investigating the factors influencing the course of HRQoL in a large representative cohort of 1968 older primary care patients in Germany. Unlike in previous studies, the change in factors that are available through primary care and influence the course of HRQoL were investigated to identify starting points for non-pharmacological interventions. Additionally, HRQoL is a subjective measurement, which might be rated very differently by individual patients due to unobserved time-constant factors, such as optimism. This can influence the independent variables, as well as the dependent variables (omitted variable bias); as such, it is crucial to control for these factors. By using fixed-effects regression analyses it was possible to control for unobserved heterogeneity and receive unbiased estimates (under the assumption of strict exogeneity). In the fixed-effects model, however, variables with little ‘within’ variation should be interpreted with some caution and promising approaches further investigated in randomised controlled trials. Nevertheless, the variation was reasonable in each variable that was investigated.
One limitation of the study is that the results are based on data from follow-up waves 2 to 5, so a selection bias of rather healthy patients — who may have remained in the study longer than less healthy patients — could not be excluded. Finally, due to the overlapping constructs of HRQoL and depression, it is not sensible to include depression in the regression analyses; it was for this reason that a separate model was calculated for patients without depression in the longitudinal analyses.
Comparison with existing literature
In this study an increase in weekly physical activity was found as the key factor to an increase in HRQoL over the course of time in the full sample, whereas walking impairment resulted in a drastically decreased HRQoL. This corresponds to a study which found that general mobility is a significant predictor of HRQoL.9 Likewise, the negative influence of increasing hearing impairment on HRQoL corresponds to earlier findings.13 Vision impairment lost significance from the cross-sectional to the longitudinal analyses model in this study, whereas Fischer and colleagues found that vision had a significant effect on HRQoL.13 The findings presented here are likely to be due to the fact that the researchers controlled for several factors, such as physical activity. Physical activity might be associated with visual impairment, because patients with visual impairment might reduce activity due to a higher risk of, for example, falls. An association of visual impairment with falls21 and with activities of daily living22 has been shown earlier. Therefore, vision impairment might not be significantly associated with HRQoL if controlled for the effect of physical activity.22
Increasing age significantly influenced HRQoL in this study; the same finding has been reached in other studies,11,12 although there are also those that did not find an age influence.9,23 This could be partly explained by the older age of our cohort, as well as the cohort of Zhang and colleagues,11 when compared with the cohort of Davis and colleagues9 (mean age at baseline 69.6 (+/− 3.0)). In old age, each additional year could have a stronger impact on HRQoL, which could be due to increasing frailty.
Factors influencing HRQoL differed in males and females (Figure 2). A mixture of different needs — as found in the study by Borglin and colleagues3 — and lower education levels in females might be reasons for this. Generally, education seems to have more influence on HRQoL than sex.
Increasing comorbidity was associated with HRQoL in the cross-sectional models but lost significance in the longitudinal analyses. The researchers have assumed that increasing functional impairment (caused by comorbidity) affects HRQoL more than increasing comorbidity itself; this corresponds with the interpretations of Blane and colleagues24 and could also explain why comorbidity has been found to be a significant predictor for HRQoL in other longitudinal studies — for example, those by Byles and colleagues7 and Zhang and colleagues11 — especially when the study used a functional comorbidity index.5,9 Although significant cross-sectional associations were detected in this study, objective memory decline, incident subjective memory impairment, and declining cognitive activity were not found to significantly influence the course of HRQoL longitudinally, with the exception of subjective memory impairment in patients with a medium level of education. The results presented here regarding objective memory decline coincide with other longitudinal studies of patients with a similar mean age,6,11 whereas Davis and colleagues found a significant impact in a younger sample (69.6 ± 3.0 years).9 Cognitive abilities above a status of dementia, therefore, do not seem to be key factors that longitudinally influence HRQoL in old age.
The results of this study showed that the HRQoL of older primary care patients who are female or less educated (primary or secondary education) is likely to decline in the subsequent 4.5 years, if they decrease their physical activity. GPs should pay special attention to these patients. Impaired ability to walk is a risk factor for a worsening HRQoL if the patient’s education level is rather low.
Patients with a high level of education may compensate for physical deficits with other abilities that may be more important to them; this could also explain why the increasing number of preserved activities of daily living (as a measure of independence) only have a positive influence on HRQoL in highly educated patients, whereas all physical impairment has no effect. Here, being able to do IADLs rather than actually doing them might influence HRQoL. In other words: physical impairment is less likely to reduce HRQoL as long as independence is preserved.
Generally, highly educated individuals might have a different perception of HRQoL, which could be due to different attitudes, expectations, and coping strategies. This could also explain why only less educated patients and those without depression benefit from living in a care home or residential home: lower expectations, as well as a positive attitude regarding care, might lead to higher satisfaction. An association between expectations and quality of life has already been assumed earlier.2
Implications for practice and research
This study aimed to investigate the non-pharmacological approaches that GPs could advise their older patients to practise in order to maintain or improve their quality of life. The results suggest that patients will benefit most of all when their ability to walk does not worsen over time. Female patients in particular, as well as patients with lower education levels, might benefit from increasing their weekly physical activities such as cycling, taking longer walks, or swimming. More research is needed to investigate which kinds of activities, and in what amounts, are effective. The same patients might also benefit from hearing aids, if mild hearing loss occurs. This has already been shown to improve the psychological components of quality of life.25,26
Patients with a low level of education (primary education) and those without depression, in particular, might benefit from moving into a nursing or retirement home; the perceived HRQoL of all other patients is not significantly negatively affected by institutionalisation (except for depressed patients). Due to small case numbers conclusions cannot be derived for patients with depression. Patients with high education levels might stabilise their HRQoL by maintaining the performance of IADLs.
Promising approaches to improve or maintain HRQoL should be further investigated in randomised controlled trials in order to confirm the findings presented here and to specify the recommendations made.