Electronic Supplementary Material Table S1

Questions included in widespread administration and subject to exploratory factor analysis.

Questions are presented in the order in which they appeared on the questionnaire during widespread administration. Items were either included and mapped to a specific factor or removed during exploratory factor analysis. Internal consistency (Cronbach’s alpha) was also tested during development of the factors, internal consistency presented in the manuscript are the results of the final reduced item questionnaire. Item removal was a dynamic process which was conducted concurrently on the older adults’ and caregivers’ data, with testing of removal of different items until an optimal factor structure was obtained with no more than 5 items in each factor (for practical reasons).

Instructions provided to participants for completion were as follows:

There are no right or wrong answers, please tick the box to indicate how strongly you agree with each of the following statements. If there are any questions that you cannot answer, or feel that it doesn’t apply to you, please skip it and move to the next question.

For the questions that ask about your/your care recipient’s doctor, please think of the doctor that prescribes the most (if not all) of your/their medicines.

Older adults’ version / Caregivers’ version / Source of question / Factor question mapped to/ Reason for removal
I like to be involved in making decisions about my medicines with my doctors / I like to be involved in making decisions about my care recipient’s medicines with their doctors / Literature [1], expert opinion and focus groups [2] / Involvement (I4)
I always ask my doctor, pharmacist or other health care professional if there is something I don’t understand about my medicines / I always ask the doctor, pharmacist or other health care professional if there is something I don’t understand about my care recipient’s medicines / Literature [3], expert opinion and focus groups [2] / Involvement (I5)
I get stressed whenever changes are made to my medicines / I get stressed whenever changes are made to my care recipient’s medicines / Literature [4] / Concerns (C3)
If my doctor recommended stopping a medicine I would want to know why / If the doctor recommended stopping one of my care recipient’s medicines I would want to know why / Expert opinion and focus groups [2] / Item loaded onto the involvement factor, removed to reduce the number of items in the factor. Chosen for removal due to low standard deviation (only 3 older adult participants out of 383 selected disagree/strongly disagree).
I would be reluctant to stop a medicine that I had been taking for a long time / I would be reluctant to stop one of my care recipient’s medicines that they had been taking for a long time / Focus groups [2] / Concerns (C1)
All people with the same medical conditions should take the same medicines / All people with the same medical conditions should take the same medicines / Expert opinion / Low cross loading onto multiple factors plus low standard deviation.
When I am feeling well I do not want to make any changes to my medicines / When the person that I care for is feeling well I do not want to make any changes to their medicines / Literature [5], expert opinion and focus groups [2] / Item loaded onto the concerns factor, removed to reduce the number of items in the factor. Chosen for removal due to lowest loading and minimal reduction of Cronbach’s alpha in both versions.
There is no time in doctor visits to discuss anything other than the current problem / There is no time in doctor visits to discuss anything other than the current problem / Literature [6], expert opinion and focus groups [2] / Loaded onto a 5th factor with other items which appeared to reflect negative feelings about medicines/health care in general. All items in this factor had low loadings (0.4-0.5) and so were removed to reduce the number of items in the questionnaire.
I have had a bad experience when stopping a medicine before / The person that I care for has had a bad experience when stopping a medicine before / Literature [7, 8], expert opinion and focus groups [2] / Concerns (C5)
A friend or family member has told me about a bad experience they have had when stopping a medicine / A friend or family member has told me about a bad experience they have had when stopping a medicine / Literature [7] and expert opinion / Low cross loadings. Highest number of missing data in both versions.
If my doctor recommended stopping a medicine I would feel that he/she was giving up on me / I feel that if I agreed to stopping one of my care recipient’s medicines then this is giving up on them / Literature [9, 10], expert opinion and focus groups [2] / Concerns (C4)
I would be happy for my GP to change a medicine that was started by a specialist / I would be happy for my care recipient’s GP to change a medicine that was started by a specialist / Literature [7] expert opinion and focus groups [2] / Did not load >0.3 on any factor.
In general, I believe the fewer medicines the better / In general, I believe the fewer medicines the better / Literature [4] and focus groups [2] / Loaded onto a 5th factor with other items which appeared to reflect negative feelings about medicines/health care in general. All items in this factor had low loadings (0.4-0.5) and so were removed to reduce the number of items in the questionnaire.
Sometimes I think I have a better grasp of what medicines I need than my doctor does / Sometimes I think I have a better grasp of what medicines the person that I care for needs than their doctor does / Literature [11, 12], expert opinion and focus groups [2] / Loaded onto a 5th factor with other items which appeared to reflect negative feelings about medicines/health care in general. All items in this factor had low loadings (0.4-0.5) and so were removed to reduce the number of items in the questionnaire.
I like to know as much as possible about my medicines / I like to know as much as possible about my care recipient’s medicines / Focus groups [2] / Involvement (I3)
I think too often medicines are prescribed and not monitored / I think too often medicines are prescribed and not monitored / Focus groups [2] / Loaded onto a 5th factor with other items which appeared to reflect negative feelings about medicines/health care in general. All items in this factor had low loadings (0.4-0.5) and so were removed to reduce the number of items in the questionnaire.
I have discussed my goals of care (expected outcomes of treatment) with my doctor / I have discussed my care recipient’s goals of care (expected outcomes of treatment) with their doctor / Literature [13], expert opinion and focus groups [2] / Item loaded onto the involvement factor, removal of the item from the factor led to an increase in Cronbach’s alpha.
No equivalent older adults question / It is difficult making treatment decisions for someone other than myself / Literature [12, 14] and focus groups [2] / Low cross loadings, was not identified to pragmatically fit within any of the factors.
No equivalent older adults question / I am aware of my care recipient’s wishes for treatment with medicines / Literature [15] and expert opinion / Item loaded onto the involvement factor, chosen for removal due to low loading.
No equivalent older adults question / There are other family members who like to be involved in decisions about medicines / Focus groups [2] / Low cross loadings, was not identified to pragmatically fit within any of the factors.
I feel that I am taking a large number of medicines / I feel that the person I care for is taking a large number of medicines / Original PATD item [16], literature [4, 17], expert opinion and focus groups [2] / Burden (B3)
I am concerned about my medicines interacting with each other / I am concerned about my care recipient’s medicines interacting with each other / Literature [4, 7, 17] and focus groups [2] / Loaded onto the burden factor in the older adults’ data (low loading), but not the caregivers’ version.
If my doctor said it was possible I would be willing to stop one or more of my regular medicines / If their doctor said it was possible I would be willing to stop one or more of my care recipient’s medicines / Original PATD item [16], expert opinion and focus groups [2] / Removed from exploratory factor analysis due to low cross loading. Retained as a global question.
I would like to reduce the number of medicines that I am taking / I would like the number of medicines that my care recipient takes to be reduced / Original PATD item [16], literature [4, 18], expert opinion and focus groups [2] / Low cross loading in the burden and appropriateness factor in the older adults’ data. Moderate loading in caregivers’ data.
I am comfortable with the number of medicines that I am taking / I am comfortable with the number of medicines that the person I care for takes / Original PATD item [16] and focus groups [2] / Low cross loading between burden and appropriateness factors.
I believe that all my medicines are necessary / I believe that all my care recipient’s medicines are necessary / Original PATD item [16], literature [7], expert opinion and focus groups [2] / Item loaded onto the appropriateness factor, chosen for removal as Cronbach’s alpha did not reduce by much upon removal.
If one of my medicines was stopped I would be worried about missing out on future benefits / There was no equivalent caregivers question. One was originally developed but was removed during piloting as optimal wording could not be gained and there were concerns from participants in relation to ‘what future?’ / Literature [7, 19] / Concerns (C2)
I believe one or more of my medicines may be currently giving me side effects / I believe one or more of my care recipient’s medicines may be currently giving them side effects / Original PATD item [16], literature [4, 7, 19-21], expert opinion and focus groups [2] / Appropriateness (A5)
I would like my doctor to reduce the dose of one or more of my medicines / I would like the doctor to reduce the dose of one or more of my care recipient’s medicines / Focus groups [2] / Appropriateness (A3)
It has taken a great deal of effort to find the right combination of medicines to manage my medical conditions / It has taken a great deal of effort to find the right combination of medicines to manage my care recipient’s medical conditions / Literature [4] and expert opinion / Cross loading
I would like to try stopping one of my medicines to see how I feel without it / I would like the doctor to try stopping one of my care recipient’s medicines to see how they feel without it / Literature [4, 7, 22] and focus groups [2] / Appropriateness (A2)
I feel that I may be taking one or more medicines that I no longer need / I feel that the person that I care for may be taking one or more medicines that they no longer need / Original PATD item [16], literature [7, 23], expert opinion and focus groups [2] / Appropriateness (A1)
I am very afraid that my medical condition(s) would return if I stopped one of my medicines / I am very afraid that my care recipient’s medical condition(s) would return if they stopped one of their medicines / Literature [7] , expert opinion and focus groups [2] / Low loading onto the concerns about stopping factor in the older adults data and low loading onto the appropriateness factor in the caregivers’ data. Pragmatically it could fit with either of these factors, but was removed as the loading was low and not consistent between the two data sets.
I would feel better about my doctor stopping one of my medicines if I knew that I could restart it / I would feel better about the doctor stopping one of my care recipients medicines if I knew that they could restart it / Literature [7] and focus groups [2] / Low cross loading which altered when different items were removed. Low standard deviation.
My doctor has never told me that I could stop one or more of my medicines / Their doctor has never told me that the person that I care for could stop one or more of their medicines / Literature [7, 10], expert opinion and focus groups [2] / Low loading.
I think it would be difficult for me to stop any of my medicines / I think it would be difficult for the person that I care for to stop any of their medicines / Literature [7], expert opinion and focus groups [2] / Loaded onto the concerns about stopping factor in the older adults data and low cross loading onto the appropriateness and burden factor in the caregivers’ data. Removed due to low cross loading in caregivers’ data.
Taking my medicines every day is very inconvenient / Giving the person that I care for their medicines every day is very inconvenient. / Literature [4, 7, 20, 21] and focus groups [2] / Burden (B2) – older adults’ version only.
Item was removed from caregivers’ version as it was determined not to be equivalent – it captures the burden to the caregiver and not to their care recipient (which the rest of the questions in the burden factor measure)
I spend a lot of money on my medicines / My care recipient’s medicines are quite expensive / Original PATD item (reworded) [16], literature [4, 20, 23], expert opinion and focus groups [2] / Burden (B1)
I can’t stop any of my medicines at the moment / The person that I care for can’t stop any of their medicines at the moment / Focus groups [2] / Low cross loading
I have a good understanding of the reasons I was prescribed each of my medicines / I have a good understanding of the reasons my care recipient was prescribed each of their medicines / Original PATD item [16], expert opinion and focus groups [2] / Involvement (I1) – older adults’ version only.
The equivalent caregivers question was removed from the involvement factor. This item did not perform in the same manner as the older adults’ item during exploratory factor analysis. On review of the question it was decided that it may not fit with the other items in the factor for the caregivers; indications are often discussed when starting medications while caregivers may take over the medication management many years after this and as such this knowledge may not be the same as their current involvement.