What is the difference between retrospective and prospective

The use of computers take place within the context of a face-to-face interview. Computer-assisted self-interviewing CASI is a technique for collecting data from participants using computers to eliminate common errors such as questionnaire routing and data entry mistakes. The use of computers take place within the context of a self-completion questionnaire. A categorical variable is a variable that can take one of a limited number of discrete values. They can be either nominal — they contain no inherent order of categories e.

Computer-assisted telephone interviewing CATI is a technique for collecting data from participants using computers to eliminate common errors such as questionnaire routing and data entry mistakes. The use of computers take place within the context of a telephone interview.

For some study participants the exact time of an event will not be known because either: the study ends or the analysis is carried out before they have had the event, or the participant drops out of the study before experiencing the event. It is therefore, only known that the event has not occurred up to the time that they were last observed in the study. Census refers to a universal and systematic collection of data from all individuals within a population.

In the UK, the government conducts a census every ten years with the next one due in A codebook is a document online or hard-copy that contains all the information about how a dataset has been coded, such that it can be deciphered by a researcher not familiar with the original coding frame.

Coding is the process of converting survey responses into numerical codes to facilitate data analysis. All potential responses as well as possible reasons for non-response for each variable are assigned numerical values according to a coding frame. Cognitive assessments are exercises used to measure thinking abilities, such as memory, reasoning and language. Cohort studies are concerned with charting the lives of groups of individuals who experience the same life events within a given time period.

The best known examples are birth cohort studies, which follow a group of people born in a particular period. Complete case analysis is the term used to describe a statistical analysis that only includes participants for which we have no missing data on the variables of interest. Participants with any missing data are excluded. Examples would include study respondents answering questions differently or even behaving differently as a result of their participation in the study.

Confounding occurs where the relationship between independent and dependent variables is distorted by one or more additional, and sometimes unmeasured, variables. A confounding variable must be associated with both the independent and dependent variables but must not be an intermediate step in the relationship between the two i. We can say that age is a confounder of that relationship as it is associated with, but not caused by, physical activity and is also associated with coronary health.

A continuous variable is a variable that has an infinite number of uncountable values e. They are also known as quantitative variables or scale variables. Cohort effects relates to changes in an outcome associated with being a member of a specific cohort of people e. In metadata management, coverage refers to the temporal, spatial and topical aspects of the data collection to describe the comprehensiveness of a dataset.

For longitudinal studies , this can relate to the topics that are covered across waves, the population to which one can generalise or the geographic extent of the dataset. Cross-sectional surveys involve interviewing a fresh sample of people each time they are carried out.

Some cross-sectional studies are repeated regularly and can include a large number of repeat questions questions asked on each survey round. Within the context of data protection , a data access agreement specifies the terms under which users are provided access to specified datasets. This usually forms part of the application process to the data controller to ensure that researchers adhere to a set of terms regarding data confidentiality , sensitivity and dissemination before accessing the data.

See also: research ethics. Data cleaning is an important preliminary step in the data analysis process and involves preparing a dataset so that it can be correctly analysed.

Data harmonisation involves retrospectively adjusting data collected by different surveys to make it possible to compare the data that was collected. This enables researchers to make comparisons both within and across studies. Repeating the same longitudinal analysis across a number of studies allows researchers to test whether results are consistent across studies, or differ in response to changing social conditions.

Data imputation is a technique for replacing missing data with an alternative estimate. There are a number of different approaches, including mean substitution and model-based multivariate approaches. Data linkage simply means connecting two or more sources of administrative, educational, geographic, health or survey data relating to the same individual for research and statistical purposes.

For example, linking housing or income data to exam results data could be used to investigate the impact of socioeconomic factors on educational outcomes. Data protection refers to the broad suite of rules governing the handling and access of information about people. Data protection principles include confidentiality of responses, informed consent of participants and security of data access.

Data structure refers to the way in which data are organised and formatting in advance of data analysis. In analysis, the dependent variable is the variable you expect to change in response to different values of your independent or predictor variables. A derived variable is a variable that is calculated from the values of other variables and not asked directly of the participants. It can involve a mathematical calculation e. Diaries are a data collection instrument that is particularly useful in recording information about time use or other regular activity, such as food intake.

They have the benefit of collecting data from participants as and when an activity occurs. As such, they can minimise recall bias and provide a more accurate record of activities than a retrospective interview. Dissemination is the process of sharing information — particularly research findings — to other researchers, stakeholders, policy makers, and practitioners through various avenues and channels, including online, written publications and events.

Dissemination is a planned process that involves consideration of target audiences in ways that will facilitate research uptake in decision-making processes and practice.

Dummy variables , also called indicator variables , are sets of dichotomous two-category variables we create to enable subgroup comparisons when we are analysing a categorical variable with three or more categories. Empirical data refers to data collected through observation or experimentation. Analysis of empirical data can provide evidence for how a theory or assumption works in practice. In metadata management, fields are the elements of a database which describes the attributes of items of data.

General ability is a term used to describe cognitive ability, and is sometimes used as a proxy for intelligent quotient IQ scores. Growth curve modelling is used to analyse trajectories of longitudinal change over time allowing us to model the way participants change over time, and then to explore what characteristics or circumstances influence these patterns of longitudinal change.

Hazard rate refers to the probability that an event of interest occurs at a given time point, given that it has not occurred before. Health assessments refers to the assessments carried out on research participants in relation to their physical characteristics or function. These can include measurements of height and weight, blood pressure or lung function.

Heterogeneity is a term that refers to differences, most commonly differences in characteristics between study participants or samples. It is the opposite of homogeneity, which is the term used when participants share the same characteristics. Where there are differences between study designs, this is sometimes referred to as methodological heterogeneity. Both participant or methodological differences can cause divergences between the findings of individual studies and if these are greater than chance alone, we call this statistical heterogeneity.

See also: unobserved heterogeneity. Household panel surveys collect information about the whole household at each wave of data collection, to allow individuals to be viewed in the context of their overall household. To remain representative of the population of households as a whole, studies will typically have rules governing how new entrants to the household are added to the study. As a way of encouraging participants to take part in research, they may be offered an incentive or a reward.

These may be monetary or, more commonly, non-monetary vouchers or tokens. Incentives are advertised beforehand and can act as an aid to recruitment; rewards are a token of gratitude to the participants for giving their time.

In analysis, an independent variable is any factor that may be associated with an outcome or dependent variable. For example, the number of hours a student spends on revision may influence their test result. A key principle of research ethics , informed consent refers to the process of providing full details of the research to participants so that they are sufficiently able to choose whether or not to consent to taking part. To put it another way, it is a measure of how thin or fat the lower and upper ends of a distribution are.

It centres on the individual and emphasises the changing social and contextual processes that influence their life over time. Many longitudinal studies focus upon individuals, but some look at whole households or organisations.

Metadata refers to data about data, which provides the contextual information that allows you to interpret what data mean. Missing data refers to values that are missing and do not appear in a dataset.

This may be due to item non-response, participant drop-out or attrition or, in longitudinal studies , some data e. Large amounts of missing data can be a problem and lead researchers to make erroneous inferences from their analysis. There are several ways to deal with the issue of missing data, from casewise deletion to complex multiple imputation models. Multi-level modelling refers to statistical techniques used to analyse data that is structured in a hierarchical or nested way.

For example. Multi-level models can account for variability at both the individual level and the group e. Non-response bias is a type of bias introduced when those who participate in a study differ to those who do not in a way that is not random for example, if attrition rates are particularly high among certain sub-groups.

Non-random attrition over time can mean that the sample no longer remains representative of the original population being studied. Two approaches are typically adopted to deal with this type of missing data : weighting survey responses to re-balance the sample , and imputing values for the missing information. Panel studies follow the same individuals over time. They vary considerably in scope and scale.

Examples include online opinion panels and short-term studies whereby people are followed up once or twice after an initial interview.

Peer review is a method of quality control in the process of academic publishing, whereby research is appraised usually anonymously by one or more independent academic with expertise in the subject. Period effects relate to changes in an outcome associated with living during a particular time, regardless of age or cohort membership e.

Piloting is the process of testing your research instruments and procedures to identify potential problems or issues before implementing them in the full study. A pilot study is usually conducted on a small subset of eligible participants who are encouraged to provide feedback on the length, comprehensibility and format of the process and to highlight any other potential issues. Population refers to all the people of interest to the study and to whom the findings will be able to be generalized e.

Owing to the size of the population, a study will usually select a sample from which to make inferences. See also: sample , representiveness. A percentile is a measure that allows us to explore the distribution of data on a variable. Of the participants contacted by phone, fall incidents were recalled by 36 Table 2 summarizes the level of agreement between these two methods.

There was therefore no underreporting, as all fallers identified using falls calendar reported falls during their telephone follow-up. Accurate falls reporting is important to ensure reliable findings in falls research and help clinicians to identify older people at risk for recurrent falling and plan for future intervention and prevention efficiently.

This current study indicates that there is an acceptable and satisfactory agreement between retrospective self-reported falls with prospective falls recording methods in both a hospital-based intervention study involving high risk falls and a community-based cohort study involving the general older population. Both prospective recording and retrospective recall yielded similar fall rates with a discrepancy of only one participant in both studies. If prospective falls recording was considered the gold standard, both over- and underestimations occurred with retrospective recall in MyFAIT, while minimal differences occurred in MELoR.

This phenomenon is also reported in previous studies 4 , 14 — Nevertheless, the level of agreement between prospective and retrospective recording were within acceptable limits, with better agreement observed in a healthier, community-based cohort compared to individuals with recurrent or injurious falls in the intervention study. Prospective recording of falls is markedly more demanding on human and financial resources and is prone to attrition In resource poor settings, this may therefore not be a reasonable solution.

Monthly fall diaries that requires monthly postal correspondence and phone calls to participants was not replicable in a large community-based cohort study. The alternative of a fall calendar yielded a low return rate, despite phone call reminders. The lack of engagement with prospective fall recording in the community cohort compared to the falls cohort may also have occurred as the falls cohort were incentivized by their involvement in a fall prevention intervention that may benefit them directly Health-seeking behavior is likely to be higher for people with illness or injuries The community cohort, on the other hand, did not receive incentives for returning their diaries and lacked the motivation of identifying falls since they had not experienced or identified falls as an issue.

While incentives are important to reduce attrition in longitudinal studies, it was not always possible to ensure adequate reward with competing priorities of a cohort study. Healthier, older adults may also perceive falls as a natural occurrence and a trivial issue related to aging 7 , reducing the likelihood of calendar returns.

The frequency of the researchers contacting the participants for reminder purpose might have an impact on the adherence of the participants to return the diary. Thus, the researchers had the opportunity to increase their effort to retrieve the diary as many as possible to explain on why the response rate is higher for the MyFAIT study.

With increasing use of electronic means of communication, the role of postal services has decreased. Therefore, older persons may not have developed a habit of posting letters, with post-boxes not being accessible to them. Alternative strategies such as the use of Smartphone Apps are not practical solutions, as the smartphone use among the Malaysian older population remains limited 19 and the App requires resources for development and maintenance.

Response rates for retrospective evaluation were higher in the community cohort than in the falls intervention study. Hospital visits were meaningful to the intervention participants and appreciated, as they received medical attention required; however, some of the frailer participants in the falls cohort had died, were no longer contactable, or were too frail to visit the hospital and may have an impact on the low response rate.

In the community cohort, limited resources and no requirement removed the possibility of hospital visits and, if conducted, would have unnecessarily inconvenienced participants. Hence, participants could only be followed up via telephone, but the response rate is much higher. The methods were, however, not comparable between studies due to the differences in participant characteristics. In addition, falls intervention study cohort consists more Chinese ethnicity who are older and have higher falls rate 11 , The ethnicity representation of more Chinese and Indian of this study compared to the national population is somewhat different However, the reason is that the two cohort studies were conducted in an urban setting where a larger proportion of the older population were ethnic Chinese and Indian Despite issues with low calendar returns in the MELoR cohort and high follow-up attrition in the MyFAIT study, falls rates returned for both retrospective and prospective data collection were similar for both studies regardless of the method of detecting falls.

The overall agreement between fall diaries and retrospective recall was moderate for MyFAIT, while calendar-recorded events and retrospective telephone recall for MELoR showed nearly perfect agreement. This implies that retrospective telephone recall should be the preferred method of detecting falls in our community cohort. However, this finding should be interpreted with caution due to the low calendar return rate for our community cohort leading to non-return bias, with individuals who remember to return diaries significantly more likely to remember their falls accurately.

While the similar falls rates for both calendar records and telephone recall are reassuring, it does not remove the possibility that calendar returners were less likely to fall while the overall cohort underreported falls Conversely, while falls rates are nearly identical between prospective diaries and retrospective recall in MyFAIT, the high attrition rates for retrospective recall should detract from the temptation to only use retrospective recall as the sole method of detecting falls.

Hence, a combination of monthly diary with self-addressed envelopes and end-of-study visit is our recommended approach to falls detection in intervention studies for secondary falls prevention. Our findings somewhat contradicted to that with previous studies, where prospective recording is a better option 14 — 16 , but similar to that of a recent study Developing countries face challenges in terms of financial constraints, lack of infrastructure, and lack of understanding about research among study participants The differences observed in our two studies could just as well be attributed to cultural diversities in perception of falls, language use, and level of education 7 , 11 , Despite emphasis on falls detection, as a strong indicator for recurrent falls, clinicians should also be aware of the prevailing opinion that primary prevention, that is, identification of increased risk of falling before any incident fall, would be preferable.

This latter approach could be aided by the use of standardized instruments and new technology 23 — Our findings has established suitable methods for recording falls, which will help alleviate mistrust on falls data recording retrospectively in community cohorts and encourage much needed falls-related research in developing countries.

There is complex explanation for this situation, as a previous study indicates that Malay ethnicity has the initiative for first action for consulting physician about their health concern 18 , and falls are highest among Indian but lowest among Malay However, the Chinese are the most in initiating self-treatment Perhaps, this may explain why the Chinese are mostly returning their calendar, as they will seek for any possible approach to resolve their sustained health issue.

This study also finds that the older people are with higher quality of life score, especially on autonomy aspect. People with better quality of life are more prone to have better health behavior 27 , and who has higher autonomy is more responsible about oneself and has control over one's own health This is translated into higher return rate of the diary among older people with better quality of life and autonomy.

One critical limitation of this study is the low return rate for prospective recording especially on the MELoR study, which may affect the reliability of falls outcomes collected in this way.

The high reliability in the MELoR study may also be due to volunteer bias; however, the impact of this is presumed not significant However, with the low response rate, and the study population comprising relatively healthy community-dwelling older people in an urban area, the generalizability of the study to rural older folks and disease-specific populations, such as those with cognitive impairment, may be limited.

Future studies should therefore target the latter populations to further establish the most suitable methods of detecting falls in these special populations. Current clinical practice recommends the confirmation of the accuracy of falls history among older persons through collateral histories from the family or carers 29 or to extrapolate falls risk based on balance and mobility functions, sensory i.

This study, however, suggests that practitioners should have confidence in self-reported or retrospective recall of falls among older patients, which should then go on to inform timely administration and early intervention of secondary prevention measures. The previous assumption that older people may conceal their falls 29 , 31 may not necessarily be of concern based on our study findings. The Asian culture has strong respect and trust to professionals and expert with little inquiry on practice Client—practitioner relationship is built on trust, and the information exchange is believed to enhance the quality of interventions 29 , 31 , Retrospective falls recall using telephone interviewing in cohort studies involving community-dwelling older adults is preferred for measuring falls in our developing country setting, with low response rates likely for prospective recording methods.

In addition, retrospective recall is the preferred method in developing countries due to its convenience and low cost. However, in intervention studies involving older fallers, a combination of prospective recording and retrospective recall should be considered. Our findings have established suitable methods for recording falls, which will help alleviate mistrust on falls data recording retrospectively in community cohorts and encourage much needed falls-related research internationally, especially in developing countries.

Requests to access these datasets should be directed to mptan ummc. All authors approved the final version of the manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Frith J, Davison J. Rev Clin Gerontol. Risk factors for falls in community stroke survivors: a systematic review and meta-analysis. Arch Phys Med Rehabil. Monitoring falls in cohort studies of community-dwelling older people: effect of the recall interval.

In academics as well as in medical research, a retrospective study refers to a study that examines backward in time, generally using medical records and interviews with patients who are already known to have a disease. This type of research uses historical data. For example, a retrospective study may involve analyzing the lifestyle choices and medical history of a group of people with type 2 diabetes. Then the researchers also study a second group of people without type 2 diabetes, and then compare the two groups.

We usually use this adjective to refer to something that is likely to happen in future. Therefore, a prospective study is the opposite of a retrospective study. This type of research looks into the future.

A prospective cohort study is a type of longitudinal study that follows a group of similar individuals over a long period of time. At the start of the research study, no one in the sample is suffering from the disease under study.