Conception of medical prescription in the elderly

Dear Editor,

Many factors determine the complex behavior of medication adherence. In addition to patients’ health and medication regimens, other factors that are likely to be important, include cognitive variables such as comprehension and recall of the medical prescription (1, 2). So, a poor adherence may be due to an inability to understand or to memorize prescriptions (3). More over, the cognitive performance seems to be a determinant cause of failing to manage a prescribed treatment ( 4., 5.). This study aimed to explore the understanding of medical prescriptions by using a cognitive psychology approach.

Medical prescriptions are procedural texts providing information under the form of condensed macropropositions (6, 7). However, there is no explicit rule for the formulation of these texts. According to the article 34 of the French code of ethics for health, the prescriber should write down clearly his recommendations and make certain that the patient understands these. Likewise, the French code of public health stipulates that medical prescriptions should contain the name, strength, dosage, form and route of administration of each drug as well as the duration of the treatment.

In order to conceive a coherent conception of the medical prescription, the patient needs to search for the relevant elements in the text of the prescription and he or she has to identify the relationship between the different elements of this text. A patient’s comprehension of the instructions relative to daily drug intake requires the integration of information about dosage and time that medications should be taken (8). This is necessary for an accurate and feasible medication adherence plan. Morrell and his colleagues (9, 10) observed that non-adherence to prescription is the result of inappropriate interpretation of drug dosage and instructions.

Individuals may understand medical prescriptions instructions with regard to their prior knowledge about drug intake. This preliminary knowledge is represented in the long-term memory as an organized schema (11). Old adults (12) and young adults (13) seem to share the same schema for medical information organization. However, Morrell and his colleagues (8, 14) suggested that difficulties in drug dosage interpretation encountered in old adults were due to the fact that medical instructions require inference, which is altered in elderly (8, 14). Consistent with this suggestion, we observed in a study (15), that old adults present reduced capacities for the recourse to inferential processes necessary for the comprehension of prescriptions and the organization of taking drugs.

In addition, the capacity decline for numerical information, observed after the age of 50 years (16), is supposed to alter the correct interpretation of dosages. Thus, it may alter prescription adherence. In older adults, working memory decline (10) could also increase the age-related differences in the comprehension of information concerning treatments. Therefore older adults may have a higher risk of errors in understanding medical prescriptions which requires interpretation to identify drug dosage and time of intake (17). Likewise, research has shown that age-related differences tend to increase with the complexity of language (18).

Our aim was thus to explore whether older are less efficient than young adults in understanding medical prescriptions and if age-related performances are related to cognitive efficiency.

Method

Subjects

We assessed a group of 14 healthy, older subjects, with no past history of neurological or psychiatric diseases. Their cognitive levels were evaluated with the MMSE (19). The older subjects were compared with a group of 14 young adults. The two groups were paired for their educational level (t(26)=1,80; NS). The average age, the educational level and the MMSE score are indicated in table 1.

Table 1.

Characteristics of old and young subject groups

	Young subjects (n=14)	Old subjects (n=14)
Age (years)
Mean	25.9	70.4
Standard deviation	5.5	3.6
Education level
(Study year number)
Mean	12.9	11.1
Standard deviation	1.5	3.2
MMSE
Mean	-	29.4
Standard deviation	-	0.9

Experimental material

Understanding of medical prescriptions was evaluated by means of a pairing task: textual representations of prescriptions and their corresponding diagrammatic representations (see figure 1 for an example). The task was a multiple-choice questionnaire, containing sixteen prescriptions of different accuracies and complexities. The instructions were to choose among three diagrams the target corresponding to a textual formulation. The total score corresponds to the number of correct answers with total of 16. The questionnaire alternated both formulations and dosages. In addition, 2 prescriptions were given describing atypical formulations (“2 pills 3 times per day; midday, evening and at bed time”) and (“3 pills 2 times per day, midday and evening”).

Figure 1.

Question n°1

Results

The results showed that older subjects were significantly less effective (mean=14,21; standard deviation=1,72) than younger individuals (mean=15,50; standard deviation=0,76) for the prescription comprehension questionnaire: t(26)=1,77, p<0,05.

Older subjects produced wrong choices for all prescriptions, but mainly for the first (“3 pills per day, before each meal”) and the sixth one (“3 pills per day, in the morning, at midday and in the evening”), while young subjects made wrong choices, only for these 2 diagrams. Performances of old subjects were lower than those of young subjects, but statistically non-significant. However, the difference between both performances were more important in the case of the question n°1 (t(26)=1,89; p=0,06) than for the question n°6 (t(26)=1,54; p=0,14).

The global cognitive evaluation by means of the MMSE (19) had a non-significant link (r=0,51; p=0,06) with the performances of the old subjects in the comprehension of the medical prescriptions, while age (r=-0,01; NS) and educational level (r=0,08; NS) did not show any link with these performances.

Discussion

Taking drugs, whether prescribed or not, is a common activity in the elderly. This is due to the combination of age-related physiological changes and the increased number of diseases with ageing. The elderly present a higher risk of non-adherence to medication than younger adults. We tried to investigate how older patients are handling drugs, through their ability to understand medical prescriptions. The used task (pairing a textual prescription to a prescription presented in diagrammatic format) may be compared with the context of patients using medical prescription in management of their daily drug intakes, in particular those having a daily or weekly medication organizer. Neither young adults nor older ones presented difficulties to count the number of pills to be taken daily. In the same way, both of them interpreted easily the diagrammatic representations even those corresponding to the most explicit formulations. Likewise, they did not show any difficulty in organizing imprecise dosages, including those corresponding to an atypical distribution (question n°15: “3 pills per day” was interpreted as one pill in the morning and two pills in the evening). The most frequent errors were in relation with prescriptions comporting a complex syntax (“3 pills per day, before each meal” and “3 pills per day, in the morning, at midday and in the evening”). We observed an important, but non-significant difference between young and old subjects for the specific prescription “3 pills per day, before each meal”, in which the daily meals were represented semantically distributed over two or four moments all over the day. Therefore, we suggested that the presence of both syntactic and semantic constraints increases the risk of error.

Meanwhile, it has to be noted that our study sample was small and our statistical results were of low significance. A more complete neuropsychological evaluation, centered on verbal and executive functioning is needed in order to confirm the role of the cognitive level in medical prescription comprehension. Further studies including a higher number of elderly and demented patients are required.

In order to confirm these preliminary results and to define recommendations for those who write prescriptions, we will need to explore patients’ comprehension of the most ambiguous prescriptions, that require integration of sever al directions: timing of drug intake, (“before each meal”, “at bedtime”), daily organization schema (X pills per day), medication’s dosage and number of daily intakes (X pills Y times a day). We should also study the relationship between collected experimental data and elderly habits, since many old subjects fail to distinguish the evening time from bedtime, which subsequently could influence their understanding of medical prescriptions.