Longitudinal study

A longitudinal study (or longitudinal survey, or panel study) is a research design that involves repeated observations of the same variables (e.g., people) over short or long periods of time (i.e., uses longitudinal data). It is often a type of observational study, although they can also be structured as longitudinal randomized experiments.[1]

Longitudinal studies are often used in social-personality and clinical psychology, to study rapid fluctuations in behaviors, thoughts, and emotions from moment to moment or day to day; in 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 cross-sectional studies, in which different individuals with the same characteristics are compared,[2] 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. 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.

When 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. 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.[3] Some of the disadvantages of longitudinal study are that they are time-consuming and expensive. Therefore, they are not convenient.[4]

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).

Cohort studies are one type of longitudinal study which sample a 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-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.[5]

Longitudinal studies do not require large numbers of participants (as in the examples below). Qualitative longitudinal studies may include only a handful of participants,[6] and longitudinal pilot or feasibility studies often have fewer than 100 participants.[7]

Examples

Study name	Type	Country or region	Year started	Participants	Remarks
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 Sax Institute. Researchers are able to analyze Study data linked to MBS and 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.
Alzheimer's Disease Neuroimaging Initiative	Panel	International	2004	n/a	–
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
The Jyväskylä Longitudinal Study of Personality and Social Development,[8] (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)[9]	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)[10]	Panel	Colombia	2010	15,363[11]	Follows rural and urban households for increasing the comprehension of social and economic changes in Colombia
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 (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 PSID study
Busselton Health Study[12]	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)[13]	Cohort	Canada	2012	1,000	Planned as a 20-year study.[14]
Child Development Project[15]	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
Congenital Heart Surgeons' Society (CHSS)	Cohort	Canada	–	5,000	Various studies, managed by the Data Center Studies on Congenital Heart Diseases
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)[16]
Footprints in Time; the longitudinal study of Indigenous children[17]	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
Genetic Studies of Genius	Cohort	United States	1921	1,528	The world's oldest and longest-running longitudinal study
Socio-Economic Panel (SOEP)	Panel	Germany	1984	12,000	–
Growing Up in Ireland (GUI)	Cohort	The Republic of Ireland	2006	8,000 children 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 Scotland (GUS)	Cohort	United Kingdom	2003	14,000[18]	Scotland
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[19]	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
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
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	–
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
National Longitudinal Surveys (NLS)	Cohort	United States	1979	12,686 (NLSY79), 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[21]	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[22]	Panel	Belgium	1992	11,000[23]	–
Panel Study of Income Dynamics	Panel	United States	1968	70,000	Possibly the oldest household longitudinal survey in the US
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 1952-1970; 639 from 1970-1992).[24]
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 [25]	–
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[26]	Cohort	United States	1957	10,317	Follows graduates from Wisconsin high schools in 1957
ONS Longitudinal Study[27][28]	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 CeLSIUS
Scottish Longitudinal Study (SLS)[29]	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 SLS-DSU
Northern Ireland Longitudinal Study (NILS)[30]	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

• Cross-sectional study
• Time series
• Repeated measures design

References

1. Shadish, William R.; Cook, Thomas D.; Campbell, Donald T. (2002). Experimental and Quasi-Experimental Designs for Generalized Causal Inference (2nd ed.). Boston, Massachusetts: Houghton Mifflin. p. 267. ISBN 0-395-61556-9.
2. Carlson, Neil R.; Miller, Harold L., Jr.; Heth, Donald S.; Donahoe, John W.; Martin, G. Neil (2009). Psychology: the Science of Behavior (7th ed.). Boston, Massachusetts: Allyn & Bacon. p. 361. ISBN 978-0-205-54786-9.
3. van der Krieke, Lian; Blaauw, Frank J.; Emerencia, Ando C.; Schenk, Hendrika M.; Slaets, Joris P.J.; Bos, Elisabeth H.; de Jonge, Peter; Jeronimus, Bertus F. (August 2016). "Temporal Dynamics of Health and Well-Being: A Crowdsourcing Approach to Momentary Assessments and Automated Generation of Personalized Feedback". Psychosomatic Medicine. Philadelphia, Pennsylvania: Lippincott Williams & Wilkins. 79 (2): 213–223. doi:10.1097/PSY.0000000000000378. PMID 27551988.
4. Cherry, Kendra. "What Is Longitudinal Research?". About.com. Retrieved 22 February 2012.
5. "What is the difference between a Panel Study and a Cohort Study?". Academia Stack Exchange. Retrieved 3 February 2016.
6. Wood, Jennifer P.; Connelly, Denise M.; Maly, Monica R. (November 2010). "'Getting back to real living': A qualitative study of the process of community reintegration after stroke". Clinical Rehabilitation. Thousand Oaks, California: SAGE Publications. 24 (11): 1045–56. doi:10.1177/0269215510375901. PMID 20713436.
7. Freeman, Joshua R.; Whitcomb, Brian W.; Roy, Amrita; Bertone‐Johnson, Elizabeth R.; Reich, Nicholas G.; Healy, Andrew J. (August 2018). "A pilot longitudinal study of anti-Müllerian hormone levels throughout gestation in low risk pregnancy". Health Science Reports. Hoboken, New Jersey: Wiley. 1 (8): e53. doi:10.1002/hsr2.53. PMC 6266452. PMID 30623089.
8. FSD. "Jyväskylä Longitudinal Study of Personality and Social Development (JYLS)". www.fsd.uta.fi. Retrieved 2017-03-30.
9. "Building a New Life in Australia (BNLA): The Longitudinal Study of Humanitarian Migrants". Department of Social Services, Australian Government. Retrieved 1 December 2016.
10. Colombian Longitudinal Survey by Universidad de los Andes (ELCA)
11. Encuesta Longitudinal Colombiaba de la Universidad de los Andes – ELCA 2013
12. "Busselton Health Study – Past Projects". BPMRI. Retrieved 1 December 2016.
13. "Canadian Longitudinal Study on Aging". Retrieved 1 December 2016.
14. Teotonio, Isabel (24 April 2012). "Landmark study on aging to follow 50,000 Canadians over the next two decades". Toronto Life. Toronto, Ontario, Canada: Toronto Star Newspapers Ltd. Retrieved 28 July 2014.
15. "Child Development Project – Developmental Pathways to Adjustment and Well-being in Early Adulthood". Durham, North Carolina: Center for Child & Family Policy – Duke University. Retrieved 1 December 2016.
16. Favela: Longitudinal Multi-Generational Study of migrants and squatters in Rio’s Favelas, 1968-2014
17. "Overview of Footprints in Time – The Longitudinal Study of Indigenous Children (LSIC)". Department of Social Services, Australian Government. Retrieved 1 December 2016.
18. Growing Up in Scotland, Study design
19. Studies, Australian Institute of Family. "Growing Up in Australia: The Longitudinal Study of Australian Children (LSAC)". Australian Institute of Family Studies (AIFS). Retrieved 1 December 2016.
20. "Manitoba Follow-up Study – About The Study". Retrieved 1 December 2016.
21. "Adoption study records of the Child Development Center Finding Aid". Archives at Yale. New Haven, Connecticut: Yale University. Retrieved 1 December 2019.
22. "Panel Study of Belgian Households". Archived from the original on 2007-02-09. Retrieved 2020-03-17.
23. Panel Study of Belgian Households, Survey summary
24. Murphy, Jane M.; Laird, Nan McKenzie; Monson, Richard R.; Sobol, Arthur M.; Leighton, Alexander H. (May 2000). "Incidence of depression in the Stirling County Study: historical and comparative perspectives". Psychological Medicine. Cambridge, Massachusetts: Cambridge University Press. 30 (3): 505–14. doi:10.1017/s0033291799002044. PMID 10883707.
25. "About the Seattle Longitudinal Study". Retrieved 1 December 2016.
26. "Wisconsin Longitudinal Study Homepage". Retrieved 1 December 2016.
27. ONS Longitudinal Study
28. Shelton, Nicola; Marshall, Chris E.; Stuchbury, Rachel; Grundy, Emily; Dennett, Adam; Tomlinson, Jo; Duke-Williams, Oliver; Xun, Wei (April 2019). "Cohort Profile: the Office for National Statistics Longitudinal Study (The LS)". International Journal of Epidemiology. Oxford, England: Oxford University Press. 48 (2): 383–384g. doi:10.1093/ije/dyy243. PMC 6469306. PMID 30541026.
29. "Home :: SLS – Scottish Longitudinal Study Development & Support Unit". Retrieved 1 December 2016.
30. "Queen's University Belfast – NILS Research Support Unit – NILS Research Support Unit". Retrieved 1 December 2016.

External links

• ESDS Longitudinal data service
• Centre for Longitudinal Studies
• National Centre for Longitudinal Data