Table 4.

Components of longitudinal data collection

	Description	Example	Frequency n (%)
1) Types of entities followed across time
Individual	Data are collected from the same individuals across time in an individual mode, e.g., individual interviews, questionnaires, diaries.	Albrecht et al. [44] investigated young adults’ experiences of chemotherapy treatment in the hospital. Seven young adults were interviewed twice, with interviews about one month apart. The young adults were also invited to keep a diary between the two interviews.	170 (56.9)
Individual case or dyads	Data are collected from cases based upon individuals or dyads. An individual case included a primary participant (e.g., patient) and secondary participants (e.g., family, health care providers). Dyads were based on two connected individuals being equally important (e.g., parents or spouses). Data consisted of individual and/or joint interviews, observations, and/or documents, etc.	Denney-Koelsch [49] investigated couples’ experiences meeting health care providers when pregnant, with a lethal fetal diagnosis. The couples took part in up to five interviews both individually and jointly during the pregnancy and after birth.	64 (21.4)
Groups	Data are collected from one or several defined groups (e.g., classes of students or health care teams). The groups are followed across time but members of the group can change during the data collection period. Data were often collected with the group, e.g., focus group interviews and/or observations, and complemented with individual interviews, questionnaires or documents.	Pyörälä et al. [50] followed two classes of students over a five year period of education. Data were collected with focus groups and open-ended questions in surveys. Some students took part in several data collection rounds whereas others contributed once during the years of the data collection period.	9 (3.0)
Settings (location/trial)	Data are collected at the same setting(s) across time. Settings can be locations (e.g., hospital wards, community centers) or trials (e.g., interventions). Articles often included several types of populations (e.g., patients, health care providers, family members). Over the data collection period, some participants contributed on several occasions, while some contributed once. Typical data collection methods included observations and/or recorded intervention sessions, combined with individual interviews, focus group interviews, questionnaires and/or documents.	Lindberg et al. [51] investigated how new technology was learned and used at an operational unit. Data were collected over four years through observations of training sessions, observations of daily work and medical procedures, observations of meetings and seminars, individual interviews with nurses, doctors, hospital technicians, physicists and technology suppliers, and documents. Some key participants took part in several parts of the data collection period, while others took part once. Frost et al. [52] investigated a home rehabilitation program for people with heart failure. Data consisted both of interviews at two time points with the same patients and caregivers, as well as audio recordings of the intervention sessions, and intervention fidelity scores. The timeline for the data collection followed the program with the last interview 12 months after baseline.	55 (18.4)
2) Tempo of data collection
Baseline and follow up	Data are collected at two points in time. Can be prospectively planned or followed up with previous data material.	Young et al. [53] conducted interviews with 60 women with genetic mutations increasing the risk for breast cancer. Three years later, 12 of the women took part in a follow up interview. The current article was built on data from both interviews with these 12 women.	70 (23.4)
Serial time points	Data are collected at several shorter engagements.	Lewis et al. [54] explored women’s experiences of trust in relation to their midwives during pregnancy. Semistructured interviews were conducted at three time-points: in early pregnancy, late pregnancy and two months post-birth.	154 (51.5)
Time waves	Data are collected during time periods with some time in between the data collection periods.	Mozaffar et al. [55] explored challenges in relation to the integration of electronic prescribing systems. Semistructured interviews were complemented with observations of meetings and documents. Data were collected in two one-month periods with about two years in between the data collection periods.	50 (16.7)
Continuous data collection	Data are collected continuously for a period of time, for example, with regular observations for several days in a row, observations of all events of a certain kind or including all documents that fulfill specific criteria.	Castro et al. [56] investigated nurses work-life narratives by analyzing nurses’ blogs. The data material consisted of all blog entries by four bloggers over a one-year period, with a total of 520 entries. Jensen et al. [47, 57] studied patients with Alzheimer’s disease who were receiving hospital care after a hip fracture. The three participants were observed for several day and evening shifts during their whole hospital stay. Observations for each participant ranged from 4 to 14 days.	23 (7.7)
3) Preplanned or adapted data collection
Preplanned data collection	The data collection is planned by the research team based upon theory, previous research and project capacity.	Nash et al. [58] investigated occupational therapy students’ changes in perspectives of frames of reference during their education. The students were interviewed at four occasions over 15 months; the interviews were scheduled at the end of each course where frames of reference were part of the curriculum.	224 (74.9)
Theoretical or analysis driven data collection	Data collection is adapted to questions raised during analysis and theoretical ideas, often using several types of data material and/or different groups of participants or stakeholders.	Bright et al., [59] investigated how health care providers engaged people with communication disabilities during rehabilitation. Data were collected in the form of observations and interviews with three patients and 28 providers. The patients were followed during the rehabilitation period for up to 12 weeks. In choosing what situations or events should be observed, the research team drew on insights from the ongoing data collection as well as previous research and theoretical notions of what situations would provide rich data.	19 (6.4)
Participant-adapted data collection	Data collection is partly preplanned but also adjusted to the individual trajectory of each participant or case to capture essential changes across time. Typically, some participants are followed more closely and for a longer period of time than other participants.	Superdock et al. [60] conducted a study about the influence of religion and spirituality on parental decision-making regarding children’s life-threatening conditions. The parents of 16 children were included as well as the children’s health care providers. The shortest individual case was followed for 6 days whereas the longest was followed for 531 days (median = 380 days). Interviews were held at the time of study enrollment and then on a monthly basis, but additional data collection was performed in the following situations: when a child had encountered a life-threatening event; when a child’s treatment had changed; when a child was discharged from the clinic; and, in some cases, a few weeks after a child’s death.	44 (14.7)
Participant entries of data	Data are independently entered by the participants. Data often consist of texts or pictures such as diary entries, think aloud methods, or answers to open-ended questions. Prompts can be sent, or participants can be encouraged to enter data in certain situations. Studies can include an entry and/or exit interview.	Gordon et al., [61] investigated experiences of the transition from trainee doctors to trained doctors. During the enrollment interview, the trainee doctors were instructed about how to provide audio diaries. Audio diaries were recorded on smartphones in order to capture thoughts and experiences in the moment. Participants received weekly reminders to provide audio diaries. In total, the audio diaries were collected over a period of 6 to 8 months and thereafter the participants took part in an exit interview.	11 (6.7)