Background
The co-occurrence of chronic conditions is a common phenomenon in the elderly and is considered to be a major threat to quality of life (QOL). Several studies report an association between the number of conditions and QOL, where a higher number of diseases is related to deterioration of physical functioning [
1‐
4], or social and psychological functioning [
5]. The prevalence rates of several conditions, including having several chronic conditions at once, increase with age [
6].
The same applies to older adults with a visual impairment or blindness. Large population-based studies in the more developed countries indicate a prevalence of visual impairment and blindness ranging from 0.6–2.1% and 0.1–0.9%, respectively [
7]. However, Klaver et al., who compared data from large prevalence studies in developed countries, showed that the prevalence of visual impairment and blindness increased rapidly after about 70 years of age [
8]. In their study, the most common causes of visual impairment and blindness were age-related cataract and age-related macular degeneration (AMD). Due to demographic aging, these numbers are expected to increase and this group of patients will cause an increased demand for ophthalmic consultations [
9]. Moreover, studies among visually impaired older patients found that co-morbidity was often reported. For example, Brody et al. found that 78% of older patients reported to have at least one other condition in addition to AMD. In our own patient population of visually-impaired older adults with a variety of eye conditions, 75% reported to have other conditions in addition to their eye disease [
10]. Langelaan et al. reported that different chronic conditions have a different impact on health-related QOL [
11]. Moreover, the combination of certain conditions may cause an additive or synergistic effect on QOL [
1,
12]. Insight into those combinations that lead to an increased QOL decline is important for the individual care of patients, and for public health purposes [
12]. For older patients with an eye condition it is not yet known which co-existing conditions lead to an increased vulnerability in terms of health-related QOL or a decline in QOL.
In addition to co-existing conditions, it is expected that other characteristics of visually impaired patients (e.g. visual acuity and socio-demographics) may also influence their health-related QOL. Another consideration is that because ophthalmologists (like other sub-specialties) have limited time per patient they mainly concentrate on the eyes and less on the broader aspects of health. Assuming that knowledge of specific factors can further assist ophthalmologists in the care of their patients, the present study aims to create a risk profile of patient characteristics and self-reported co-existing conditions which predict a relatively rapid deterioration in health-related QOL.
Discussion
Our study aimed to provide a risk profile for visually impaired older patients related to a change in QOL. First, when not taking specific risk factors into account, for the entire group there was no significant change in health-related QOL between baseline and five-month follow-up, as measured with the EQ-5Dindex. However, we expected this result to be an underestimation of the decline in QOL because patients with worse scores were lost to follow-up. With the risk profile presented in this study it was possible to determine patients at risk for a relatively rapid decline in QOL, in addition to patients who already experienced a low QOL. Patients who reported at baseline to have diabetes, COPD/asthma, consequences of stroke, musculoskeletal conditions, cancer, gastrointestinal conditions or higher logMAR Visual Acuity values (which means more vision loss) experienced a lower QOL after five months compared to patients who did not report those conditions or who had lower logMAR Visual Acuity values. Patients reporting those conditions (besides their eye condition) or patients with more vision loss can be considered target groups who need more attention. Ophthalmologists may consider referral to another sub-specialty if the patient is currently not under treatment for the condition(s) that they have reported. A referral by the ophthalmologist or optometrist to a multidisciplinary rehabilitation service seems appropriate for patients with multiple conditions. In addition to reading aids, these patients may need occupational therapy, specialized mobility training, more extensive training for using low-vision aids or help from a social worker, to adapt to their visual disability. Furthermore, in visually impaired older patients we found that having COPD/asthma, consequences of stroke, musculoskeletal conditions or more vision loss predicted a relatively rapid decline in QOL between baseline and five-month follow-up. The fact that patients with diabetes, cancer and gastrointestinal conditions did not show a further decline in QOL might indicate that they were under treatment by a clinician or general practitioner during the study period.
Our results concur with those of Sprangers et al., who explored the relative impact of diseases on QOL in a large group of patients with a wide range of chronic conditions [
23]. They reported that patients with gastrointestinal, cerebrovascular and musculoskeletal conditions experienced the most detrimental impact, those with visual impairments and chronic respiratory conditions experienced an intermediate impact and, for example, hearing impairments or dermatological conditions appeared to result in a relatively favorable impact [
23].
The results of our study showed that visually impaired older patients frequently suffer from one or more co-existing conditions (other than their eye condition), and that these patients experienced a lower health-related QOL than patients without any self-reported conditions at baseline. However, it has been reported that clinicians find it difficult to appreciate the impact of low vision on QOL [
24]. Therefore, it might be helpful for ophthalmologists to understand that low vision and those specific co-existing conditions cause a measurable extra burden or even a rapid decline in QOL in older patients. These older patients already experience a worse QOL than, for example, younger visually impaired patients; this was shown by comparison with reference populations among visually impaired adults [
11], and older adults in the general Dutch population [
21]. In contrast, the fact that our visually impaired older patients were referred to rehabilitation services by their ophthalmologist (e.g. to an optometrist or to a multidisciplinary service) demonstrates that the ophthalmologist was at least aware of the disabling problems caused by the low vision of their patients. Although a referral did not necessarily increase the patient's health-related QOL (which is not expected from low-vision rehabilitation services), an improvement was observed in some of the vision-related QOL domains. In a previous non-randomized study among the same group of visually impaired older patients, we used a disease-specific questionnaire to measure the effect of low vision rehabilitation in terms of vision-related QOL [
13]. These latter patients showed an improvement on the 'reading small print' dimension after five months, for both rehabilitation types (optometrist/multidisciplinary service). Patients who went to the multidisciplinary center also improved on the 'adjustment' to vision loss dimension after five months. Both dimensions were part of the Low Vision Quality of Life questionnaire [
25]. On this questionnaire, the 'basic aspects' of vision, vision-related 'mobility' and 'visual (motor) skills' dimensions did not change significantly after five months. In general, rehabilitation for patients with irreversible eye conditions is recommended. For example, in the case of AMD there is usually no medical treatment available so that rehabilitation is the only option to adjust to living with a visual disability.
Our study has some limitations. Co-morbidity was assessed with an open-ended question, and this questioning method can result in under-reporting compared to more specific methods [
26]. Open-ended questions are considered sub-optimal for assessing the prevalence of co-existing conditions, because in that case mainly the serious conditions are reported [
27]. In our study it is feasible that the visually impaired older patients reported those conditions that had the most impact on their QOL at the time of the measurements. Moreover, when we investigated the reliability of the self-reported conditions we observed that between baseline and follow-up the reports on co-morbidity were not stable. One reason for this was loss to follow-up, and the other was that the patients did not continue to report the co-existing conditions which they had reported at baseline. Moreover, some patients reported co-existing conditions for the first time at the follow-up measurement. It is not clear whether these changes in self-reports reflect a true change, or simply a lack of reports at baseline for which the reasons are not clear. It is possible that patients were not aware of their condition at both of the measurement points, either because the symptoms were absent or because they had problems with recollection. Alternatively, at follow-up the patients might have thought that the researchers were already aware of their co-existing conditions because they had reported them at baseline; in this case they might have considered it superfluous to report their (chronic) co-existing condition(s) a second time. In contrast, Klabunde et al. showed that patients were generally able to provide reliable reports of their co-existing conditions over time; however, arthritis had the highest proportion of inconsistent responses [
28]. More insight into the validity of self-reported co-morbidity in open-ended questions was revealed from our previous study. In that study, for most condition categories there was a lack of agreement between co-morbidity reports of patients and those of their GP; the agreement differed per condition, where patients mostly under-reported. However, for diabetes, COPD/asthma and heart conditions we found very good to moderate agreement between the patients and the GPs [
10].
The current study did not include a thorough investigation of the nature of open-ended questions. More research is needed to establish the reliability of open versus closed-ended questions administered by patients. Pre-structured questionnaires are available [
29], which should provide a more complete view of the patient's co-morbidity than open-ended questions [
27]; these are easier to complete by older patients because they depend less on the recollection ability of the patients. We do note, however, that open-ended questions give a more accurate reflection of how co-morbidity is usually addressed in a clinical setting [
26]. Although we do not have exact information concerning the patient's co-morbidity, in the clinic one is also confronted with the incompleteness of patient reports. Nevertheless, we found that self-reported co-morbidity from open-ended questions predicted a decline in QOL, with results comparable to those of larger studies [
23].
Finally, the EQ-5D is one of the most widely used generic index measures of health-related QOL [
30] and is increasingly used as a stand-alone measure [
31]. The questionnaire allowed us to gain insight into various health states, to compare different sub-groups of our patient population, and to compare our study population with two reference groups. However, the EQ-5D has been criticized for having only three response categories per dimension, which could lead to lack of measurement precision and responsiveness (see e.g. Pickard et al.) [
32]. For example, on the mobility dimension it seems to be a large step for patients to choose between the response categories 2) and 3): where 1) represents no problems with walking about, 2) moderate problems with walking about, and 3) being confined to bed. Therefore, the results of our study on QOL decline may even be an underestimation of the actual QOL decline in visually impaired older patients. Furthermore, in the field of ophthalmology and low vision it is increasingly more common to use Rasch analysis or other item response theory models to calculate health-related outcome measures, such as QOL questionnaires [
13,
33,
34]. Some efforts have been made to use Rasch analyses on the five dimensions to validate the EQ-5D [
32]; however, problems still exist with these valuations and they have not yet been widely accepted. For comparability purposes it has been recommended to follow the original validated and widely used valuations [
30].
Conclusion
We believe that the knowledge of specific co-existing conditions is important for public health, the patient's individual care and the ophthalmologist whose patients consist mainly of older adults. Patient's self-reported co-morbidity and other characteristics may influence the ophthalmologist's medical decision-making concerning surgery, or their approach to older patients who often have complicated drug regimens [
35]. Although our results should be confirmed in an additional study with pre-structured co-morbidity questionnaires, this study shows that visually impaired older patients with specific co-existing conditions and low vision experienced a lower QOL at follow-up or were at higher risk of a rapid decline in QOL.
In conclusion, we recommend to actively ask visually impaired older patients about their musculoskeletal conditions, COPD/asthma and consequences of stroke, and to continue referring patients with low vision to rehabilitation services, according to the guidelines developed in the USA [
36] and in the Netherlands [
9]. With a risk profile, as presented in this study, a rehabilitation intervention or a specific referral to another sub-specialty may be of benefit for the health and vision-related QOL of the patient and for the involvement of ophthalmologists in their patient's general health.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
RMAVN drafted the manuscript and performed all statistical analyses; MRDB participated in the design of the study, collected data, advised on the statistical analyses, and helped to interpret the data; JGJH drafted a preliminary version of the manuscript and performed data analyses; PJR helped to draft the manuscript and revised the manuscript for important intellectual content; GHMBVR conceived of the study and its design; helped to draft the manuscript, and has given final approval of the version to be published; All authors read and approved the final manuscript.