Longitudinal study

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A longitudinal survey is a correlational research study that involves repeated observations of the same variables over long periods of time — often many decades. It is a type of observational study. Longitudinal studies are often used in psychology to study developmental trends across the life span, and in sociology to study life events throughout lifetimes or generations. The reason for this is that, unlike cross-sectional studies, in which different individuals with same characteristics are compared,[1] longitudinal studies track the same people, and therefore the differences observed in those people are less likely to be the result of cultural differences across generations. Because of this benefit, longitudinal studies make observing changes more accurate, and they are applied in various other fields. In medicine, the design is used to uncover predictors of certain diseases. In advertising, the design is used to identify the changes that advertising has produced in the attitudes and behaviors of those within the target audience who have seen the advertising campaign.

Because most longitudinal studies are observational, in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect causal relationships than experiments. But because of the repeated observation at the individual level, they have more power than cross-sectional observational studies, by virtue of being able to exclude time-invariant unobserved individual differences, and by virtue of observing the temporal order of events. Some of the disadvantages of longitudinal study include the fact that they take a lot of time and are very expensive. Therefore, they are not very convenient.[2]

Longitudinal studies allow social scientists to distinguish short from long-term phenomena, such as poverty. If the poverty rate is 10% at a point in time, this may mean that 10% of the population are always poor, or that the whole population experiences poverty for 10% of the time. It is impossible to conclude which of these possibilities is the case using one-off cross-sectional studies.

Types of longitudinal studies include cohort studies and panel studies. Cohort studies sample a cohort, defined as a group experiencing some event (typically birth) in a selected time period, and studying them at intervals through time. Panel studies sample a cross-section, and survey it at (usually regular) intervals.

A retrospective study is a longitudinal study that looks back in time. For instance, a researcher may look up the medical records of previous years to look for a trend.


Study nameTypeCountry or RegionYear startedParticipantsRemarks
Alzheimer's Disease Neuroimaging InitiativePanelInternational2004n/a-
Avon Longitudinal Study of Parents and Children (ALSPAC)CohortUnited Kingdom199114,000-
Born in BradfordCohortUnited Kingdom200712,500-
1970 British Cohort Study (BCS70)CohortUnited Kingdom197017,000Monitors the development of babies born in the UK in one particular week in April 1970
British Household Panel SurveyPanelUnited Kingdom1991n/aModeled on the US PFID study
Busselton Health StudyPanelAustralia196610,000-
Caerphilly Heart Disease StudyCohortUnited Kingdom19792,512Male subjects (Wales)
Canadian Longitudinal Study on Aging (CLSA-ÉLCV)CohortCanada20121,000Planned as a 20-year study.[3]
Child Development ProjectCohortUnited States1987585Follows children recruited the year before they entered kindergarten in three cities: Nashville and Knoxville, TN and Bloomington, Indiana
Children of Immigrants Longitudinal Study (CILS)CohortUnited States19925,262Florida
Congenital Heart Surgeons' Society (CHSS)CohortCanada-5,000Various studies, managed by the Data Center Studies on Congenital Heart Diseases
Dunedin Multidisciplinary Health and Development StudyCohortNew Zealand19721,037Participants were all born in 1972
Study of migrants and squatters in Rio’s FavelasCohortBrazil1968n/aThe work of Janice Perlman, reported in her book, Favela (2014)[4]
Fragile Families and Child Wellbeing StudyCohortUnited States1998n/aStudy being conducted in 20 cities
Framingham Heart StudyCohortUnited States19485,209Massachusetts
Genetic Studies of GeniusCohortUnited States19211,528The world's oldest and longest-running longitudinal study
Socio-Economic Panel (SOEP)PanelGermany198412,000-
Growing Up in Scotland (GUS)CohortUnited Kingdom200314,000[5]Scotland
Health and Retirement StudyCohortUnited States198822,000-
Household, Income and Labour Dynamics in Australia SurveyPanelAustralia200125,000-
Human Speechome ProjectCohortUnited States20051Single participant was the son of the researcher, studying language development. Project concluded in 2008.
Study of Australian ChildrenCohortAustralia200410,000-
Luxembourg Income Study (LIS)CohortInternational1983n/a30 countries
Midlife in the United StatesCohortUnited States19836,500-
Millennium Cohort Study (MCS)CohortUnited Kingdom200019,000Study of child development, social stratification and family life
Millennium Cohort StudyCohortUnited States2000200,000Evaluation of long-term health effects of military service, including deployments
Minnesota Twin Family StudyCohortUnited States198317,000 (8,500 twin pairs)-
National Child Development Study (NCDS)CohortUnited Kingdom195817,000-
National Longitudinal Surveys (NLS)CohortUnited States1979NLSY79-12,686, NLSY97-approx. 9000Icludes 4 Cohorts: NLSY79 (Born 1957-64), NLSY97 (Born 1980-84), NLSY79 Children and Young Adults, National Longitudinal Surveys of Young Women and Mature Women (NLSW)
National Longitudinal Survey of Children and Youth (NLSCY)CohortCanada199435,795-
Pacific Islands Families StudyCohortNew Zealand20001,398-
Panel Study of Belgian HouseholdsPanelBelgium199211,000[6]-
Panel Study of Income DynamicsPanelUnited States196870,000Possibly the oldest household longitudinal surveys in the US
Rotterdam StudyCohortNetherlands199015,000Focus is on inhabitants of Ommoord, a suburb of Rotterdam
Seattle 500 StudyCohortUnited States1974500Study of the effects of prenatal health habits on human development
Study of Health in PomeraniaCohortGermany199715,000Investigates common risk factors, sub-clinical disorders and manifest diseases in a high-risk population
Irish Longitudinal Study on Ageing (TILDA)CohortIreland20098,500Studies health, social and financial circumstances of older Irish population
New Zealand Attitudes and Values Study-New Zealand2009n/a-
Seattle Longitudinal StudyCohortUnited States19566,000 [7]-
Understanding Society: The UK Household Longitudinal StudyPanelUnited Kingdom2009100,000Incorporates the British Household Panel Survey
Up SeriesCohortUnited Kingdom196414Documentary film project by Michael Apted
Study on Global Ageing and Adult Health (SAGE)CohortInternational200265,964Studies the health and well-being of adult populations and the ageing process in six countries: China, Ghana, India, Mexico, Russian Federation and South Africa
Wisconsin Longitudinal StudyCohortUnited States195710,317Follows graduates from Wisconsin high schools in 1957

See also[edit]


  1. ^ Carlson, Neil and et al. "Psychology the Science of Behavior", p. 361. Pearson Canada, United States of America
  2. ^ Cherry, Kendra. "What Is Longitudinal Research?". experiments. About.com guide. Retrieved 22 February 2012. 
  3. ^ Teotonio, Isabel (24 April 2012). "Landmark study on aging to follow 50,000 Canadians over the next two decades". Toronto Life (Toronto Star Newspapers Ltd.). Retrieved 28 July 2014. 
  4. ^ Favela: Longitudinal Multi-Generational Study of migrants and squatters in Rio’s Favelas, 1968-2014
  5. ^ Growing Up in Scotland, Study dsign
  6. ^ Panel Study of Belgian Households, Survey summary
  7. ^ About the Seattle Longitudinal Study

External links[edit]