Table 4 Barriers to participation and drop-out or refusal rates of participants

Appointment non-attendance

14.0% of passive refusals

[40]

2.1% of males that refused to participate

[58]

1.3% of males were unable to cope with study requirements due to old age

[58]

Comprehension of the study requirements

0.4% of males refused to participate

[58]

Cannot be bothered/not interested

27.8% of active refusals

[40]

13.8% declined to participate

[41]

66.7% refused to participate

[44]

39.6% males that refused to participate

[58]

18.5% of eligible participants

[49]

Did not meet inclusion criteria

87% of eligible participants

[49]

Time commitment

38.9% of active refusals

[40]

26.3% of males that refused to participate

[58]

Invasion of privacy

0.3% of males that refused to participate

[58]

Medical

15.5% of participants who refused to participate

[57]

35.6% of participants unable to attend due to illness, 0.2% of participants had limited medical information

[40]

16.9% of males that refused to participate

[58]

Unable to contact/no response

35.0% of eligible participants

[40]

17.4% of eligible participants

[41]

40.7% of invited male participants

[61]

Psychopathology factors

0.8% of males refused to participant in case a medical problem was uncovered

[58]

Reluctance over medical testing

1.1% of males that refused to participate

[58]

Religious/philosophical reasons

0.1% of males that refused to participate

[58]

Third party involvement

62.2% of participants passively refused via a relative, 15.9% of participants passively refused by resident/nursing home

[40]

18.4% transferred to another ward or discharged from hospital or research nurse forgot to ask

[44]

Unknown reason/personal reason

5.2% of males that refused to participate

[58]

9.5% of eligible participants in 1968

[45]

28.6% of active refusals

[40]

3.2% of eligible participants

[41]

3.6% of eligible participants

[49]

Proportion of participants who were non-completers/Further suggestions for improvements by completing participants

Appointment non-attendance

3.2% of non-completers

[41]

24.7% missed at least one visit by end of study (12 months)

[52]

Quantitative data- in person visits were difficult to attend due to the distance of the centre

[53]

Communication

Qualitative data- better coordination of communication for study results to participants

[38, 49]

Qualitative data- increased personalisation would increase engagement like a personal question the participants could contemplate over the next week

[49]

Qualitative data- increase of data sharing between research team, treatment therapist and each participant would have increased engagement and data tracking over the period

[49]

Education

Qualitative data- Increasing the education around the condition that is the focus of the trial

[38]

Medical

12.7% non-completers

[57]

4.1% of non-completers had a child that had an additional diagnosis

[51]

Qualitative data- state of the participants personal health and the nature of the intervention may affect future enrolment

[38]

Situational (lack of reliable housing, moving, death)

1.4% of non-completers

[57]

95.2% of non-completers

[42]

1.4% of non-completers from wave 1 (1974) to 47.3% in wave 5 (2011)

[45]

6.8% to 30.6% of non-completers across 6 different centres

[61]

25.7% of non-completers moved, 5.4% of families had a child who died

[51]

21.4% of non-completers died, 17.4% moved away

[36]

2.3%—9.4% of non-completers (wave 1–5)

[39]

Qualitative data- unable to complete exercise or have appropriate meal preparation

[53]

63.4% of non-completers

[55]

35.5% of non-completers died

[48]

Inability to adhere to study activities

Qualitative data- unable to complete training due to unreliable technology

[53]

12.7% of non-completers

[57]

10.1% did not receive allocation of intervention

[41]

1.7% of non-completers did not like research assessment, 0.8% of non-completers were incarcerated

[48]

Cannot be bothered/ loss of interest/wanted to withdraw

40.8% of non-completers

[36]

9.5% of non-completers

[51]

3.2% of non-completers

[44]

20.6% of non-completers

[61]

13.2% of non-completers

[48]

Difficulty to arrange follow-up appointments with participants

6.8% of non-completers

[51]

20.6% of non-completers

[48]

Missing data/incomplete data

6.5% of participants

[41]

52.5% of participants did not complete the final postal survey, 0.36% of participants did not have available data in the Finnish national Care Register for Health Care

[44]

15.0% of non-completers

[61]

3.1% of participants

[43]

Time commitment

5.6% of non-completers

[57]

17.6% of non-completers

[51]

Qualitative data- competing demands in personal life, unable to prioritize program participation

[53]

Qualitative data- 24-h urine output collection during work hours was difficult and restrictive, taking days of work and losing wages

[38]

Lost contact

8.5% of non-completers

[57]

27.8% of non-completers

[44]

1.7% of non-completers

[48]

Unknown reason/personal reason

7.0% of non-completers

[57]

4.8% of non-completers

[42]

4.8% of non-completers

[44]

21.6% of non-completers

[51]

20.9% of non-completers from wave 1 (1974) to 24.1% in wave 5 (2011)

[45]

10.7% of non-completers

[56]

57.5% of non-completers were lost by 1-year follow up

[46]

16.5% of non-completers

[48]

Difficulty in comprehending the study

2.7% of non-completers

[51]

Qualitative data- reducing length and complexity of questionnaires and understanding the potential risks

[38]

Psychopathology factors

Paranoid factor had an elevated but non-significant risk for early drop out (26.9%) Dysphoric Borderline factor put a significant risk for late dropout (15.9%)

[50]

Qualitative data- side effects from medications for mental health or chronic pain were issues in completing the program. Social anxiety of talking openly to other participants also prohibited some participants interaction

[53]

Third party involvement

6.8% of non-completers – due to family issues

[51]

Qualitative data- consider withdrawing when family was sick

[38]

4.2% of non-completers—Work and family responsibilities

[48]

Financial Hardship

Qualitative data- participants across all treatment groups found recommendations of what to eat and how to exercise cost prohibitive

[53]

Qualitative data- providing monetary incentives

[38]

Technical Issues

Qualitative data- difficulties in troubleshooting web-based program after logging in as well as printing physical activity log

[53]