Personality and unachieved treatment goals related to poor adherence to asthma medication in a newly developed adherence questionnaire – a population-based study

The current study sought to develop a questionnaire with discriminatory power to measure adherence to asthma medication in adult individuals with asthma. An item pool was constructed that was based on our previous research and knowledge focusing adherence. Based on individuals with asthma randomly selected from the general population, who completed the initial questionnaire, ten items were selected and a revised version of the questionnaire was evaluated among another group of individuals with asthma also randomly selected from the general population. The final questionnaire contains three subscales- “medication routines”, “self-adjusting the medication” and “concerns about side-effects -, of which two correlated well with an established adherence questionnaire. The personality traits Neuroticism and Conscientiousness were associated with the subscale “medication routines”. Respondents who had not achieved their goals with the asthma medication reported poorer adherence.

The removal of several items that were regarded as having high/low endorsement was made to increase the possibility of discriminating the reported adherence. For instance, the MARS [25] has shown a skewed distribution in previous research [12, 14, 29], which could result in an overestimation of adherence. Consequently, the removal of the items with high/low endorsement was considered as a measure to enable a good response spread to facilitate the identification of high or low adherers, which could be viewed as an advantage with the developed questionnaire. The removal of the items could also be regarded as a limitation because it may affect both the respondents’ reporting on their beliefs and the distribution of their positions.

One strength is that the items in the final questionnaire were selected through analyses based on data derived from individuals with asthma selected at random from the general population. The focus of any questionnaire must be relevant to its target group [23], and participants in the current study consisted of individuals with asthma who had reported use of asthma medication, which could be a strength considering representativeness. However, as adherence to medication treatment tends to fluctuate over time, it may be a possible limitation that the current study did not provide data on the duration of the medication treatment. Moreover, the response-rate could have been higher, which could be seen as a shortcoming considering representativeness as it may be that those who chose to participate were those who were attentive to the medication treatment. Nevertheless, the sample sizes in both phase 1–3 (each with at least 100 participants) were considered sufficiently large enough. In addition, both samples were selected at random from a population-based study, which in turn consisted of participants selected at random, which could be regarded as a strength [27].

An additional strength of the current study may be that the questionnaire developed in phase 1 was tested in phase 2 and that the validity of the final questionnaire was tested in relation to a previously validated instrument, i.e. the MARS [25]. Responses to all items in the subscales “medication routines and “self-adjusting the medication” correlated with the responses to the MARS, which could be considered an appropriate validity check. It could be seen as a shortcoming that the developed questionnaire was not tested in relation to a more objective measure of adherence, for instance electronic monitoring of medication use. The scale “medication concerns” was not associated with the MARS, and thus removal of this subscale may be called for. However, concerns with asthma medication are to be regarded as one influencing factor of adherence [29].

Regarding personality and adherence, the current showed that the scale “medication routines” in the developed questionnaire – was associated with the personality traits Neuroticism and Conscientiousness. These findings are consistent with previous research focusing on personality traits and adherence to asthma medication [12–14] but also with adherence in relation to other long-term medication treatments [30–33]. Individuals who score higher on Neuroticism have reported poorer adherence to asthma medication treatment [14] and in relation to other long-term therapies [20, 33]. The personality trait Neuroticism measures degrees of emotional stability. Persons scoring higher on this trait could be more inclined to be worried, anxious, depressive and vulnerable to stress [15], which are characteristics that may explain the poorer adherence among individuals scoring higher on Neuroticism. Anxiety and depression, which are prevalent among individuals with asthma [34], have previously been associated with poorer adherence to asthma medication treatment [35]. For future studies, it would be advisable to include measures of anxiety and depression when assessing adherence to asthma medication treatment.

In contrast to Neuroticism, individuals scoring higher on Conscientiousness have reported higher adherence both in relation to asthma medication treatment [13, 14] and other medication treatments [30–33]. Importantly, the current study shows that individuals who had reached their goals with the asthma medication also reported better adherence, which indicates that adherence is of significance if personal goals with the asthma medication are to be achieved. Therefore, the current study suggests that individual goals with the asthma medication are discussed with the patients during follow-up consultations and that the set goals are used as inducement to promote adherence.