Sampling planning

It was estimated that a sample size of 103 in each group will have 80% power to detect a difference in means of 2.5 assuming that the common standard

deviation is 6.35 using a two-sample t-test with a 5% two sided significance level. The difference in means was based on Perceived Stress Scale (PSS-10) (the primary outcome) normative data from a large national probability sample⁹³. The actual value of 2.5 was derived from the socio demographic categories; 1) Number of people in household (greater than four children in a household versus no children in a household) and 2) Number of children in household (greater than five people in a household versus one person in a household). These two demographic categories were thought to be closest to the stressful demands subject providing practical support to a stroke survivor would be likely to face. To account for anticipated drop out of 10%, 115 exposed and 115 unexposed participants were the target numbers for each exposed and unexposed group.

3.3.4 Participants

3.3.4.1 Inclusion criteria

Participants in both exposed and non exposed cohorts had to be at least 16 years of age, free from any informal care-giving activities in excess of 20 hours per week for example to an elderly dependent relative or a disabled child, able to speak English and mentally capable of participating in a longitudinal study at their cohort entry date.

3.3.4.2 Exclusion criteria

Participants in both the exposed and non exposed cohorts were excluded if they indicated that the presence of one or more clinical conditions from the Charlson comorbidity index⁹⁴ which would suggest serious ill health.

3.3.4.3 Identification and recruitment of the potentially exposed cohort Eligible participants were all people who identified themselves as likely to be the main provider of care to patients with a clinical diagnosis of stroke who had been admitted to one of the three hospital stroke units and have a post hospital discharge destination of a private address. Engagement in what is necessary for the health, welfare, maintenance and protection of the stroke survivor/ care recipient was confirmed at three and six months after the stroke patient was discharged from hospital by questionnaire. The questionnaire included a series of questions covering the types of activities of daily living that the subject may provide regular help with and, the estimated number of hours care per week that they give help or support to the person that they care for.

After referral or identification following routine screening of a possible stroke patient, the attending clinician or the stroke specialist nurse was contacted to confirm the clinical diagnosis. Stroke patients were excluded if they had a terminal illness (e.g., cancer, heart disease, chronic obstructive pulmonary disease) with a predicted survival of less than six months as estimated by their physician, had a diagnosis of subarachnoid haemorrhage or were resident in a long-term care facility, residential facility or nursing home prior to admission to

a stroke unit, or were being discharged to a long-term care facility, residential facility or nursing home.

Eligible stroke patients were monitored routinely during hospital visiting hours to identify family, friends or neighbours who may engage in the provision of help and support to the stroke patient after discharge from hospital. Medical, nursing and therapy staff also notified the researchers of potentially eligible family, friends or neighbours.

A consecutive sample of potentially eligible participants was provided with written information (see appendix 1) about the GCCS and the opportunity to discuss the study with the principal investigator should they wish. Once the potential participant had consented (see appendix 2) to participate they were asked to complete the eligibility screening questionnaire (see appendix 3). The eligibility screening questionnaire included questions on: 1) whether the person completing the form is likely to be the main person providing the help or support to the stroke survivor; 2) the extent of existing care giving commitments to family members, friends, neighbours or others because of long-term physical or mental ill health or disability, or problems related to old age; and 3) the

presence of clinical conditions included in the Charlson Index⁹⁴. Potentially exposed participants who met the inclusion criteria were then asked to complete the baseline questionnaire (see appendix 4). The method of returning all the forms was agreed at each stage with the potential participant. Methods of return included in person to the principal investigator or a member of staff from the Scotland Stroke Research Network (SSRN)⁹⁵; by post using the stamped addressed envelope provided; or to leave it in the in-tray in the stroke unit clearly marked ‘for the attention of the principal investigator GCCS’ or 'for the attention of SSRN staff member'.

The nature of the recruitment process i.e., consent before screening for eligibility was found to be upsetting for some potential recruits as many who were keen to participate discovered following screening that they were ineligible because of their existing care-giving commitments. Therefore, if it were possible, the researchers identified people who were likely to be at risk of exclusion following screening either through discussions with medical, nursing or therapy staff or an informal discussion with the potential participants. These

potential participants were provided with the same written information but the inclusion and exclusion criteria were highlighted to them.

3.3.4.4 Identification and recruitment of reference group

Age sex matched unexposed subjects were recruited from a general practitioners list of patients, through the Scottish Primary Care Research Network (SPCRN)⁹⁶ funded by the Chief Scientist Office (CSO) and run by the Scottish School of Primary Care, University of Glasgow. Potential age sex matched unexposed subjects were identified by the SPCRN’s research officer from the general

practitioner’s information technology system (GPASS) using a programme written in Excel. In the first instance, for every one person identified as providing

practical support to a stroke survivor, ten potential age sex matched subjects were identified and written to. When that recruitment strategy failed to attract sufficient numbers, the ratio of potential age sex matched pair members was increased to one to twenty.

All potential age sex matched pair members were contacted initially by letter from a general practitioner (See appendix 5). This letter informed the potential matched pair member about the study and asked them to return an ‘expression of interest’ form (see appendix 6) in the stamped addressed envelope (SAE) provided directly to the principal investigator, indicating if they were interested or would like more information before deciding to proceed. Every potential matched pair member who responded was sent a letter (see appendix 7), full study information (see appendix 8), a consent form (see appendix 9) and an SAE.

They were also provided with my contact details including telephone number and email address, should they wish to discuss the study or any concerns they may have. When potential matched pair members did call for further

information or to discuss concerns, their telephone number was noted and they were called back immediately. Once potential matched pair members had consented to participate, a screening form (see appendix 10) was sent out with an SAE. When participants failed to meet the inclusion criteria, they were contacted by telephone and the reason for exclusion was explained. Potential matched pair members who met the inclusion criteria were sent a letter, the baseline questionnaire and an SAE (see appendix 11).

Each matched pair member was recruited and consented within one year of the exposed participant providing practical care.

It was possible for a non-exposed participant to become exposed during follow-up.

For details of the results of recruitment based on matching see Table 3-2 Matching characteristics, page 3-83.

3.3.4.5 The Scotland Stroke Research Network and recruitment The study was formally adopted by the Scotland Stroke Research Network (SSRN), whose objectives include helping,

“...expedite the efficient and timely coordination of high quality clinical studies, including their approval, start-up and also

recruitment to target and timescale.”⁹⁷

Adoption by the SSRN therefore provided more resources for recruitment.

3.3.5 Follow-up

Follow-up was at three and six months after enrolment. A postal questionnaire was sent out to exposed participants and non exposed participants at each time point.