View source for Social:Longitudinal study

{{short description|Study with repeated observations over time}}
A '''longitudinal study''' (or '''longitudinal survey''', or '''panel study''') is a [[Research design|research design]] that involves repeated observations of the same variables (e.g., people) over long periods of time (i.e., uses longitudinal data). It is often a type of [[Observational study|observational study]], although it can also be structured as longitudinal [[Randomized experiment|randomized experiment]].<ref>{{cite book|last1=Shadish|first1=William R.|last2=Cook|first2=Thomas D.|last3=Campbell|first3=Donald T. |title=Experimental and Quasi-Experimental Designs for Generalized Causal Inference|url=https://archive.org/details/experimentalquas00shad|url-access=limited|date=2002|publisher=Houghton Mifflin|location=Boston, Massachusetts|isbn=0-395-61556-9|page=[https://archive.org/details/experimentalquas00shad/page/n286 267]|edition=2nd}}</ref>

Longitudinal studies are often used in social-personality and [[Social:Clinical psychology|clinical psychology]], to study rapid fluctuations in behaviors, thoughts, and emotions from moment to moment or day to day; in [[Social:Developmental psychology|developmental psychology]], to study developmental trends across the life span; and in sociology, to study life events throughout lifetimes or generations; and in consumer research and political polling to study consumer trends. The reason for this is that, unlike [[Social:Cross-sectional study|cross-sectional studies]], in which different individuals with the same characteristics are compared,<ref>{{cite book |first1=Neil R.|last1=Carlson| first2=Harold L. Jr. |last2=Miller|first3=Donald S.|last3=Heth|first4=John W.|last4=Donahoe|first5=G. Neil|last5=Martin |title=Psychology: the Science of Behavior |publisher=Allyn & Bacon |location=Boston, Massachusetts|isbn=978-0-205-54786-9 |date=2009|edition=7th | pages = 361 }}</ref> longitudinal studies track the same people, and so the differences observed in those people are less likely to be the result of cultural differences across generations, that is, the [[Social:Cohort effect|cohort effect]]. Longitudinal studies thus make observing changes more accurate and 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. 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.

Longitudinal studies can be retrospective (looking back in time, thus using existing data such as medical records or claims database) or prospective (requiring the collection of new data).{{citation needed|date=May 2017}}

[[Cohort study|Cohort studies]] are one type of longitudinal study which sample a [[Cohort (statistics)|cohort]] (a group of people who share a defining characteristic, typically who experienced a common event in a selected period, such as birth or graduation) and perform [[Cross-sectional data|cross-section]] observations at intervals through time. However, not all longitudinal studies are cohort studies, as longitudinal studies can instead include a group of people who do not share a common event.<ref>{{cite web|url=http://academia.stackexchange.com/questions/54017/what-is-the-difference-between-a-panel-study-and-a-cohort-study|title=What is the difference between a Panel Study and a Cohort Study?|website=Academia Stack Exchange|access-date=3 February 2016}}</ref>

== Advantages ==
When longitudinal studies are [[Observational study|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 [[Causality|causal relationships]] than [[Experiment|experiment]]s. However, 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 also of observing the temporal order of events.<ref>{{cite journal |last1=van der Krieke |first1=Lian |last2=Blaauw |first2=Frank J. |last3=Emerencia |first3=Ando C. |last4=Schenk |first4=Hendrika M. |last5=Slaets |first5=Joris P.J. |last6=Bos |first6=Elisabeth H. |last7=de Jonge |first7=Peter |last8=Jeronimus |first8=Bertus F. |date=August 2016 |title=Temporal Dynamics of Health and Well-Being: A Crowdsourcing Approach to Momentary Assessments and Automated Generation of Personalized Feedback |journal=Psychosomatic Medicine |location=Philadelphia, Pennsylvania |publisher=Lippincott Williams & Wilkins |volume=79 |issue=2 |pages=213–223 |doi=10.1097/PSY.0000000000000378 |pmid=27551988 |s2cid=10955232|url=https://pure.rug.nl/ws/files/40193705/00006842_201702000_00011.pdf }}</ref>{{Failed verification|date=August 2020|reason=looked at article and can't seem to find this language and not clearly a good source for such information}} 

Longitudinal studies do not require large numbers of participants (as in the examples below). Qualitative longitudinal studies may include only a handful of participants,<ref>{{cite journal |last1=Wood |first1=Jennifer P. |last2=Connelly |first2=Denise M. |last3=Maly |first3=Monica R. |date=November 2010 |title='Getting back to real living': A qualitative study of the process of community reintegration after stroke |journal=Clinical Rehabilitation |location=Thousand Oaks, California |publisher=SAGE Publications |volume=24 |issue=11 |pages=1045–56 |doi=10.1177/0269215510375901 |pmid=20713436 |s2cid=40295472}}</ref> and longitudinal pilot or feasibility studies often have fewer than 100 participants.<ref>{{cite journal |last1=Freeman |first1=Joshua R. |last2=Whitcomb |first2=Brian W. |last3=Roy |first3=Amrita |last4=Bertone-Johnson |first4=Elizabeth R. |last5=Reich |first5=Nicholas G. |last6=Healy |first6=Andrew J. |date=August 2018 |title=A pilot longitudinal study of anti-Müllerian hormone levels throughout gestation in low risk pregnancy |journal=Health Science Reports |location=Hoboken, New Jersey |publisher=[[Company:Wiley (publisher)|Wiley]] |volume=1 |issue=8 |pages=e53 |doi=10.1002/hsr2.53 |pmc=6266452 |pmid=30623089}}</ref>

== Disadvantages ==
Longitudinal studies are time-consuming and expensive.<ref name="Longitudinal study">{{cite web |last=Cherry |first=Kendra |title=What Is Longitudinal Research? |url=http://psychology.about.com/od/lindex/g/longitudinal.htm |access-date=22 February 2012 |website=About.com}}</ref>

Longitudinal studies cannot avoid an attrition effect: that is, some subjects cannot continue to participate in the study for various reasons. Under longitudinal research methods, the reduction in the research sample will bias the remaining smaller sample.

Practice effect is also one of the problems: longitudinal studies tend to be influenced because subjects repeat the same procedure many times (potentially introducing [[Autocorrelation|autocorrelation]]), and this may cause their performance to improve or deteriorate.

==Examples==
{| class="wikitable sortable"
|-
! Study name
! Type
! Country or region
! Year started
! data-sort-type="number"| Participants
! class="unsortable"| Remarks

|-
|[https://www.saxinstitute.org.au/our-work/45-up-study/ 45 and Up Study]
|Cohort
|Australia
|2006
|267,153
|The 45 and Up Study is a longitudinal study of participants aged 45 years and over in New South Wales conducted by the [https://www.saxinstitute.org.au/ Sax Institute]. Researchers are able to analyze Study data linked to [http://www.mbsonline.gov.au/internet/mbsonline/publishing.nsf/Content/Home MBS] and [http://www.health.gov.au/internet/main/publishing.nsf/Content/Pharmaceutical+Benefits+Scheme+%28PBS%29-1 PBS] data, the NSW cancer registry, State hospitalizations, and emergency department visits and mortality data.
The Study is used by both researchers and policymakers to better understand how Australians are aging and using health services to prevent and manage ill-health and disability and guide health system decisions. 45 and Up is the largest ongoing study of healthy aging in the Southern Hemisphere.
|-
| [[Biology:Alzheimer's Disease Neuroimaging Initiative|Alzheimer's Disease Neuroimaging Initiative]]
| Panel
| International
| 2004
| n/a
| –
|-

| [[Medicine:Australian Longitudinal Study on Women's Health|Australian Longitudinal Study on Women's Health]] (ALSWH)
| Cohort
| Australia
| 1996
| 50,000
| Includes four cohorts of women: born between 1921 and 1926, 1946–1951, 1973–1978 and 1989–1995
|-
|[[Medicine:Nurses' Health Study|Nurses' Health Study]]
|Cohort
|United States
|1976
|275,000
|Most expensive and largest observational health study in history
|-
|The Jyväskylä Longitudinal Study of Personality and Social Development,<ref>{{Cite web|url=http://www.fsd.uta.fi/en/data/background/jyls/|title=Jyväskylä Longitudinal Study of Personality and Social Development (JYLS)|last=FSD|website=www.fsd.uta.fi|access-date=2017-03-30}}</ref> (JYLS)
|Cohort
|Finland
|1968
|369
|The sample was drawn from 12 complete school classes. Data has been collected when the participants were 8, 14, 20, 27, 33, 36, 42 and 50 years old.
|-
| Building a New Life in Australia : The Longitudinal Study of Humanitarian Migrants (BNLA)<ref>{{cite web|url=https://www.dss.gov.au/our-responsibilities/families-and-children/programmes-services/building-a-new-life-in-australia-bnla-the-longitudinal-study-of-humanitarian-migrants|title=Building a New Life in Australia (BNLA): The Longitudinal Study of Humanitarian Migrants |publisher= Department of Social Services, Australian Government|access-date=1 December 2016}}</ref>
| Cohort
| Australia
| 2013
| 2,399
| A longitudinal study of the settlement experience of humanitarian arrivals in Australia
|-

| Colombian Longitudinal Survey by Universidad de los Andes (ELCA)<ref>[https://encuestalongitudinal.uniandes.edu.co/ Colombian Longitudinal Survey by Universidad de los Andes] (ELCA)</ref>
| Panel
| Colombia
| 2010
| 15,363<ref>[https://encuestalongitudinal.uniandes.edu.co/images/stories/Archivos/Doc_CEDE-ELCA/dcede2014-42.pdf Encuesta Longitudinal Colombiaba de la Universidad de los Andes – ELCA 2013]{{Dead link|date=October 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
| Follows rural and urban households for increasing the comprehension of social and economic changes in Colombia
|-
| [[Organization:Avon Longitudinal Study of Parents and Children|Avon Longitudinal Study of Parents and Children]] (ALSPAC)
| Cohort
| United Kingdom
| 1991
| 14,000
| –
|-
| [[Born in Bradford]]
| Cohort
| United Kingdom
| 2007
| 12,500
| –
|-
| [[1970 British Cohort Study|1970 British Cohort Study]] (BCS70)
| Cohort
| United Kingdom
| 1970
| 17,000
| Monitors the development of babies born in the UK in one particular week in April 1970
|-
| [[British Doctors Study]] 
| Cohort
| United Kingdom
| 1951
| 40,701
| Monitored the health of British male doctors.  It provided convincing evidence of the link between smoking and cancer.
|-
| British Household Panel Study
| Panel
| United Kingdom
| 1991
| 5,500 households (~10,000 individuals)
| Modeled on the US Panel Study of Income Dynamics [[Panel Study of Income Dynamics|PSID study]]
|-
| [[Medicine:Busselton Health Study|Busselton Health Study]]<ref>{{cite web|url=http://bpmri.org.au/research/key-projects-studies/busselton-health-study-2/busselton-health-study-past-projects.html|title=Busselton Health Study – Past Projects |date=14 May 2014 |publisher= BPMRI |access-date=1 December 2016}}</ref>
| Panel
| Australia
| 1966
| 10,000
| –
|-
| [[Caerphilly Heart Disease Study]]
| Cohort
| United Kingdom
| 1979
| 2,512
| Male subjects (Wales)
|-
| Canadian Longitudinal Study on Aging (CLSA-ÉLCV)<ref>{{cite web|url=http://www.clsa-elcv.ca/|title=Canadian Longitudinal Study on Aging |access-date=1 December 2016}}</ref>
| Cohort
| Canada
| [https://www.clsa-elcv.ca/about-us/history#:~:text=In%20December%202011%2C%20the%20CLSA,2012%20with%20French%2Dspeaking%20participants. 2011]
| All research participants will be followed until 2033 or death.<ref>{{Cite journal |last1=Raina |first1=Parminder |last2=Wolfson |first2=Christina |last3=Kirkland |first3=Susan |last4=Giffith |first4=Lauren E. |last5=Balion |first5=Cynthia |last6=Cossette |first6=Benoît |last7=Dionne |first7=Isabelle |last8=Hofer |first8=Scott |last9=Hogan |first9=David |last10=van den Heuvel |first10=Edwin R. |date=Dec 2019 |title=Cohort profile: the Canadian Longitudinal Study on Aging (CLSA) |url=https://doi.org/10.1093/ije/dyz173 |journal=International Journal of Epidemiology |volume=48 |issue=6 |pages=1753 |doi=10.1093/ije/dyz173|pmid=31633757 |pmc=6929533 }}</ref>
|-
| Child Development Project<ref>{{cite web|url=http://childandfamilypolicy.duke.edu/project/child-development-project-developmental-pathways-to-adjustment-and-well-being-in-early-adulthood/|title=Child Development Project – Developmental Pathways to Adjustment and Well-being in Early Adulthood |publisher= Center for Child & Family Policy – Duke University |location=Durham, North Carolina|access-date=1 December 2016}}</ref>
| Cohort
| United States
| 1987
| 585
| Follows children recruited the year before they entered kindergarten in three US cities: Nashville and Knoxville, Tennessee, and Bloomington, Indiana
|-
| Children of Immigrants Longitudinal Study (CILS)
| Cohort
| United States
| 1992
| 5,262
| Florida
|-
| [[Organization:Congenital Heart Surgeons' Society|Congenital Heart Surgeons' Society]] (CHSS)
| Cohort
| Canada
| –
| 5,000
| Various studies, managed by the Data Center Studies on Congenital Heart Diseases
|-
| [[Social:Dunedin Multidisciplinary Health and Development Study|Dunedin Multidisciplinary Health and Development Study]]
| Cohort
| New Zealand
| 1972
| 1,037
| Participants born in Dunedin during 1972–73
|-
| Study of migrants and squatters in Rio's Favelas
| Cohort
| Brazil
| 1968
| n/a
| The work of Janice Perlman, reported in her book ''Favela'' (2014)<ref>{{Cite web |url=http://www.themegacitiesproject.org/ |title=Favela: Longitudinal Multi-Generational Study of migrants and squatters in Rio's Favelas, 1968-2014 |access-date=2014-04-17 |archive-date=2018-08-09 |archive-url=https://web.archive.org/web/20180809185930/http://themegacitiesproject.org/ |url-status=dead }}</ref>
|-
| Footprints in Time; the longitudinal study of Indigenous children<ref>{{cite web|url=https://www.dss.gov.au/about-the-department/national-centre-for-longitudinal-studies/overview-of-footprints-in-time-the-longitudinal-study-of-indigenous-children-lsic|title=Overview of Footprints in Time – The Longitudinal Study of Indigenous Children (LSIC) |publisher= Department of Social Services, Australian Government|access-date=1 December 2016}}</ref>
| Cohort
| Australia
| 2008
| 1,680
| Study of Aboriginal and Torres Strait Islander children in selected locations across Australia
|-
| Fragile Families and Child Wellbeing Study
| Cohort
| United States
| 1998
| n/a
| Study being conducted in 20 cities
|-
| [[Framingham Heart Study]]
| Cohort
| United States
| 1948
| 5,209
| Massachusetts
|-
| [[Philosophy:Genetic Studies of Genius|Genetic Studies of Genius]]
| Cohort
| United States
| 1921
| 1,528
| The world's oldest and longest-running longitudinal study
|-
| [[Organization:Socio-Economic Panel|Socio-Economic Panel]] (SOEP)
| Panel
| Germany
| 1984
| 12,000
| –

|-
|[https://www.growingup.ie/about-growing-up-in-ireland/ Growing Up in Ireland] (GUI)
|Cohort
|The Republic of Ireland
|2006
|8,000 children<br>10,000 infants
|''Growing Up in Ireland'' is an Irish Government-funded study of children being carried out jointly by the Economic and Social Research Institute and Trinity College Dublin. The study started in 2006 and follows the progress of two groups of children: 8,000 9-year-olds (Child Cohort/Cohort ’98) and 10,000 9-month-olds (Infant Cohort/Cohort ’08).
|-
| [[Growing Up in New Zealand]] (GUiNZ)
| Cohort
| New Zealand
| 2009
| 6,846 children

|
''GUiNZ'' is New Zealand's largest ongoing longitudinal study. It follows approximately 11% of all NZ children born between 2009 and 2010.<ref>{{Cite news|last=Walters|first=Laura|date=15 May 2018|title=Budget 2018: $2m for NZ's biggest longitudinal study about growing up in NZ|work=Stuff|url=https://www.stuff.co.nz/national/politics/103901353/budget-2018-2m-for-nzs-biggest-longtitudinal-study-about-growing-up-in-nz#:~:text=The%20Government%20has%20announced%20almost,receive%20more%20than%20%241.9m.|access-date=8 April 2021}}</ref> The study aims to look in depth at the health and well-being of children (and their parents) growing up in NZ.

|-
|[https://growingupinscotland.org.uk/ Growing Up in Scotland] (GUS)
|Cohort
|Scotland
|2003
|14,000
|Scotland
|-
| [[Social:Health and Retirement Study|Health and Retirement Study]]
| Cohort
| United States
| 1988
| 22,000
| –
|-
| Household, Income and Labour Dynamics in Australia Survey
| Panel
| Australia
| 2001
| 25,000
| –
|-
| Grant Study
| Cohort
| United States
| 1939
| 268
| A 75-year longitudinal study of 268 physically and mentally healthy Harvard college sophomores from the classes of 1939–1944.
|-
| Growing Up in Australia; the longitudinal study of Australian children<ref>{{cite web|url=http://www.growingupinaustralia.gov.au/index.html|title=Growing Up in Australia: The Longitudinal Study of Australian Children (LSAC) |first=Australian Institute of Family|last=Studies|publisher= Australian Institute of Family Studies (AIFS)|access-date=1 December 2016}}</ref>
| Cohort
| Australia
| 2004
| 10,000
| –
|-
| Midlife in the United States
| Cohort
| United States
| 1983
| 6,500
| –
|-
| Manitoba Follow-Up Study (MFUS)
|Cohort
|Canada
|1948
|3,983 men
|Canada's largest and longest running investigation of cardiovascular disease and successful aging
|-<ref>{{cite web|url=http://www.mfus.ca/About.php|title=Manitoba Follow-up Study – About The Study|access-date=1 December 2016}}</ref>
|-
| [[Millennium Cohort Study]] (MCS)
| Cohort
| United Kingdom
| 2000
| 19,000
| Study of child development, social stratification, and family life
|-
| Millennium Cohort Study
| Cohort
| United States
| 2000
| 200,000
| Evaluation of long-term health effects of military service, including deployments
|-
| [[Biology:Minnesota Twin Family Study|Minnesota Twin Family Study]]
| Cohort
| United States
| 1983
| 17,000 (8,500 twin pairs)
| –
|-
| [[National Child Development Study]] (NCDS)
| Cohort
| United Kingdom
| 1958
| 17,000
| –

|-
|[https://www.neps-data.de/Mainpage National Educational Panel Study] (NEPS)
|Cohort
|Germany
|2009
|60,000
|Study on the development of competencies, educational processes, educational decisions, and returns to education in formal, nonformal, and informal contexts throughout the life span
|-
| [[Social:National Longitudinal Surveys|National Longitudinal Surveys]] (NLS)
| Cohort
| United States
| 1979
| 12,686 (NLSY79),<br>9,000 (approx., NLSY97)
| Includes four 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)
| Cohort
| Canada
| 1994
| 35,795
| Inactive since 2009
|-
| National Health and Nutrition Examination Survey (NHANES)
| Cohort
| United States
| 1971
| 8,837 (since 1999)
| Continual since 1999
|-
| Nature vs Nurture study
| Cohort
| United States
| 1960
| 11<ref>{{cite web |title=Adoption study records of the Child Development Center Finding Aid |url=https://archives.yale.edu/repositories/12/resources/3434/collection_organization |website=Archives at Yale |publisher=[[Organization:Yale University|Yale University]]|location=New Haven, Connecticut|access-date=1 December 2019}}</ref>
| Concluded in 1980. Controversial study by Peter B. Neubauer of twins and triplets separated at birth. Never published.
|-
| [[Pacific Islands Families Study]]
| Cohort
| New Zealand
| 2000
| 1,398
| –
|-
| Panel Study of Belgian Households<ref>{{Cite web |url=http://www.psbh.be/ |title=Panel Study of Belgian Households |access-date=2020-03-17 |archive-url=https://web.archive.org/web/20070209073541/http://www.psbh.be/ |archive-date=2007-02-09 |url-status=dead }}</ref>
| Panel
| Belgium
| 1992
| 11,000<ref>Panel Study of Belgian Households, [http://www.lisdatacenter.org/wp-content/uploads/our-lis-documentation-by-be00-survey.pdf Survey summary]</ref>
| –
|-
| [[Panel Study of Income Dynamics]]
| Panel
| United States
| 1968
| 70,000
| Possibly the oldest household longitudinal survey in the US
|-
|[https://rainestudy.org.au The Raine Study]
|Cohort
|Australia
|1989
|5,768 (Gen1 + Gen2)<br>750 (Gen3)<br>100 (Gen0)
|The Raine Study is based in Perth, Western Australia. It has followed the same group of pregnant women (Gen1) and their babies (Gen2) who were born into the study between 1989 and 1992. Its original aim was to investigate the benefits of more frequent ultrasound scans on infant health.<ref>{{Cite journal|date=1993-10-09|title=Effects of frequent ultrasound during pregnancy: a randomised controlled trial|url=https://www.sciencedirect.com/science/article/abs/pii/014067369391944H|journal=The Lancet|language=en|volume=342|issue=8876|pages=887–891|doi=10.1016/0140-6736(93)91944-H|issn=0140-6736|last1=Newnham|first1=J.P.|last2=Evans|first2=S.F.|last3=Michael|first3=C.A.|last4=Stanley|first4=F.J.|last5=Landau|first5=L.I.|pmid=8105165|s2cid=11763088}}</ref> It now studies the impact that early life factors (from the womb onwards) have on health throughout life.<ref>{{Cite journal|last1=McKnight|first1=Charlotte M.|last2=Newnham|first2=John P.|last3=Stanley|first3=Fiona J.|last4=Mountain|first4=Jenny A.|last5=Landau|first5=Louis I.|last6=Beilin|first6=Lawrence J.|last7=Puddey|first7=Ian B.|last8=Pennell|first8=Craig E.|last9=Mackey|first9=David A.|date=2012|title=Birth of a cohort — the first 20 years of the Raine study|url=https://onlinelibrary.wiley.com/doi/abs/10.5694/mja12.10698|journal=Medical Journal of Australia|language=en|volume=197|issue=11–12|pages=608–610|doi=10.5694/mja12.10698|pmid=23230915|s2cid=43704496|issn=1326-5377}}</ref> The Raine Study now includes 4 generations of cohort members.
|-
| [[Rotterdam Study]]
| Cohort
| Netherlands
| 1990
| 15,000
| Focus is on inhabitants of Ommoord, a suburb of Rotterdam
|-
| [[Seattle 500 Study]]
| Cohort
| United States
| 1974
| 500
| Study of the effects of prenatal health habits on human development
|-
| Stirling County Study
| Cohort
| Canada
| 1952
| 639
| Long-term study epidemiology of psychiatric disorders. Two cohorts were studied (575 from 1952 to 1970; 639 from 1970 to 1992).<ref>{{cite journal |first1=Jane M.|last1=Murphy|first2=Nan McKenzie|last2=Laird|first3=Richard R.|last3=Monson|first4=Arthur M.|last4=Sobol|first5=Alexander H.|last5=Leighton | title = Incidence of depression in the Stirling County Study: historical and comparative perspectives | journal = Psychological Medicine | publisher={{wipe|Cambridge University Press}}|location=Cambridge, Massachusetts|volume = 30 | issue = 3 | pages = 505–14 | date = May 2000 | pmid = 10883707 | doi = 10.1017/s0033291799002044 |s2cid=40645927}}</ref>
|-
| Study of Health in Pomerania
| Cohort
| Germany
| 1997
| 15,000
| Investigates common risk factors, sub-clinical disorders and manifest diseases in a high-risk population
|-
|-
| [[Study of Mathematically Precocious Youth]]
| Cohort
| United States
| 1972
| 5,000
| Follows highly intelligent people identified by age 13.
|-
| Survey of Health, Ageing, and Retirement in Europe (SHARE)
| Panel 
| Europe
| 2002
| 120,000
| Multidisciplinary and cross-national panel database of micro data on health, socio-economic status and social and family networks of individuals aged 50 or over
|-
| Irish Longitudinal Study on Ageing (TILDA)
| Cohort
| Ireland
| 2009
| 8,500
| Studies health, social and financial circumstances of the older Irish population
|-
| New Zealand Attitudes and Values Study
| –
| New Zealand
| 2009
| n/a
| –
|-
| Seattle Longitudinal Study
| Cohort
| United States
| 1956
| 6,000 <ref>{{cite web|url=https://sharepoint.washington.edu/uwsom/sls/about/Pages/default.aspx|title=About the Seattle Longitudinal Study|access-date=1 December 2016}}</ref>
| –
|-
| [[Social:UK households: a longitudinal study|Understanding Society: The UK Household Longitudinal Study]]
| Panel
| United Kingdom
| 2009
| 100,000
| Incorporates the British Household Panel Study
|-
| ''[[Up Series]]''
| Cohort
| United Kingdom
| 1964
| 14
| Documentary film project by Michael Apted
|-
| Study on Global Ageing and Adult Health (SAGE)
| Cohort
| International
| 2002
| 65,964
| Studies 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 Study<ref>{{cite web|url=http://www.ssc.wisc.edu/wlsresearch/|title=Wisconsin Longitudinal Study Homepage|access-date=1 December 2016}}</ref>
| Cohort
| United States
| 1957
| 10,317
| Follows graduates from Wisconsin high schools in 1957
|-
| ONS Longitudinal Study<ref>[http://www.ons.gov.uk/ons/guide-method/user-guidance/longitudinal-study/index.html ONS Longitudinal Study]</ref><ref>{{cite journal |first1=Nicola|last1=Shelton|first2=Chris E.|last2=Marshall|first3=Rachel|last3=Stuchbury|first4=Emily|last4=Grundy|first5=Adam|last5=Dennett|first6=Jo|last6=Tomlinson|first7=Oliver|last7=Duke-Williams|first8=Wei|last8=Xun|title = Cohort Profile: the Office for National Statistics Longitudinal Study (The LS) | journal = International Journal of Epidemiology | publisher=[[Organization:Oxford University Press|Oxford University Press]]|location=Oxford, England|volume = 48 | issue = 2 | pages = 383–384g | date = April 2019 | pmid = 30541026 | pmc = 6469306 | doi = 10.1093/ije/dyy243 }}</ref>
| Panel 
|England and Wales
|1974 (data from 1971)
|500,000 (1% sample of the population of England and Wales). The LS contains records on over 500,000 people usually resident in England and Wales at each point in time)
|The sample comprises people born on one of four selected dates of birth and therefore makes up about 1% of the total population. The sample was initiated at the time of the 1971 Census, and the four dates were used to update the sample at the 1981,1991, 2001 and 2011 Censuses and in routine event registrations. Fresh LS members enter the study through birth and immigration and existing members leave through death and emigration. Thus, the LS represents a continuous sample of the population of England and Wales, rather than a sample taken at a one-time point only. It now includes records for over 950,000 study members. In addition to the census records, the individual LS records contain data for events such as deaths, births to sample mothers, emigrations and cancer registrations. Census information is also included for all people living in the same household as the LS member. However, it is important to emphasize that the LS does not follow up household members in the same way from census to census. Support for potential users and more information available at [http://www.ucl.ac.uk/celsius CeLSIUS]
|-
|Scottish Longitudinal Study (SLS)<ref>{{cite web|url=http://sls.lscs.ac.uk/|title=Home :: SLS – Scottish Longitudinal Study Development & Support Unit|access-date=1 December 2016}}</ref>
|Panel
|Scotland
|1991
|274,000 (comprises 5.3% sample of the Scottish population, with records on approximately 274,000 individuals using 20 random birthdates)
| The SLS is a large-scale linkage study built upon census records from 1991 onwards, with links to vital events (births, deaths, marriages, emigration); geographical and ecological data (deprivation indices, pollution, weather); primary and secondary education data (attendance, Schools Census, qualifications); and links to NHS Scotland ISD datasets, including cancer registrations, maternity records, hospital admissions, prescribing data and mental health admissions. The research potential is considerable. The SLS is a replica of the ONS Longitudinal Study but with a few key differences: sample size, commencement point and the inclusion of certain variables. The SLS is supported and maintained by the SLS Development & Support Unit with a safe-setting at the National Records of Scotland in Edinburgh. Further information and support for potential users is available at [http://sls.lscs.ac.uk/ SLS-DSU]
|-
| Northern Ireland Longitudinal Study (NILS)<ref>{{cite web|url=http://www.qub.ac.uk/research-centres/NILSResearchSupportUnit/|title=Queen's University Belfast – NILS Research Support Unit – NILS Research Support Unit|access-date=1 December 2016}}</ref>
| Panel 
| Northern Ireland
| 2006 
| 500,000 (comprises about 28% of the Northern Ireland population and approximately 50% of households).
| The NILS is a large-scale, representative data-linkage study created by linking data from the Northern Ireland Health Card Registration system to 1981, 1991, 2001 and 2011 census returns and to administrative data from other sources. These include vital events registered with the General Register Office for Northern Ireland (such as births, deaths, and marriages) and the Health Card registration system migration events data. The result is a 30-year-plus longitudinal data set which is regularly being updated. In addition to this rich resource, there is also the potential to link further Health and Social care data via distinct linkage projects (DLPs). The NILS is designed for statistics and research purposes only and is managed by the Northern Ireland Statistics and Research Agency under Census legislation. The data are de-identified at the point of use; access is only from within a strictly controlled ‘secure environment’ and governed by protocols and procedures to ensure data confidentiality.
|-
|Early Childhood Longitudinal Study (ECLS)
|
| United States
|
|
|
|}

== See also ==
* [[Social:Cross-sectional study|Cross-sectional study]]
* [[Time series]]
* [[Panel analysis]]
* [[Repeated measures design]]

== References ==
{{Reflist}}

== External links ==
*[https://web.archive.org/web/20100214111340/http://www.esds.ac.uk/longitudinal/access/introduction.asp ESDS Longitudinal data service]
*[http://www.cls.ioe.ac.uk Centre for Longitudinal Studies]
*[https://www.dss.gov.au/about-the-department/national-centre-for-longitudinal-data National Centre for Longitudinal Data]

{{Medical research studies}}


[[Category:Research methods]]
[[Category:Statistical data types]]
[[Category:Design of experiments]]
[[Category:Cohort study methods]]
[[Category:Social research]]

{{Sourceattribution|Longitudinal study}}