Longitudinal study
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 often a type of observational study, although they can also be structured as longitudinal randomized experiments.[1] 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 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.
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. 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.[3]
Longitudinal studies allow social scientists to distinguish short from longterm 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 by using one-off cross-sectional studies.
Types of longitudinal studies include panel studies and cohort studies. Cohort studies sample a cohort, defined as a group experiencing some event (typically birth) in a selected time period, performing a cross-section at intervals through time. Panel studies also use cross-sectional data and compare the same group of individuals at intervals through time, but the sample is not necessarily a cohort, as it can be a group of people that do not share a common event. Therefore, a cohort study can be considered a panel study, but a panel study is not always a cohort study.[4]
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.
Examples
| Study name | Type | Country or region | Year started | Participants | Remarks | |
|---|---|---|---|---|---|---|
| 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 1921-1926, 1946-1951, 1973-1978 and 1989-1995 | |
| Building a New Life in Australia: The Longitudinal Study of Humanitarian Migrants (BNLA) | Cohort | Australia | 2013 | 2399 | a longitudinal study of the settlement experience of humanitarian arrivals in Australia | |
| Colombian Longitudinal Survey by Universidad de los Andes (ELCA) | Panel | Colombia | 2010 | 15,363[5] | 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 Household Panel Survey | Panel | United Kingdom | 1991 | n/a | Modeled on the US PFID study | |
| Busselton Health Study | 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) | Cohort | Canada | 2012 | 1,000 | Planned as a 20-year study.[6] | |
| Child Development Project | Cohort | United States | 1987 | 585 | Follows children recruited the year before they entered kindergarten in three cities: Nashville and Knoxville, TN 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)[7] | |
| Footprints in TIme; the longitudinal study of Indigenous children | Cohort | Australia | 2008 | 1680 | 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 Scotland (GUS) | Cohort | United Kingdom | 2003 | 14,000[8] | Scotland | |
| Health and Retirement Study | Cohort | United States | 1988 | 22,000 | - | |
| Household, Income and Labour Dynamics in Australia Survey | Panel | Australia | 2001 | 25,000 | - | |
| Human Speechome Project | Cohort | United States | 2005 | 1 | Single participant was the son of the researcher, studying language development. Project concluded in 2008. | |
| Growing Up in Australian; the longitudinal study of Australian children | Cohort | Australia | 2004 | 10,000 | - | |
| Luxembourg Income Study (LIS) | Cohort | International | 1983 | n/a | 30 countries | |
| 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 Longitudinal Surveys (NLS) | Cohort | United States | 1979 | NLSY79-12,686, NLSY97-approx. 9000 | Includes 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) | 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 | |
| Pacific Islands Families Study | Cohort | New Zealand | 2000 | 1,398 | - | |
| Panel Study of Belgian Households | Panel | Belgium | 1992 | 11,000[9] | - | |
| Panel Study of Income Dynamics | Panel | United States | 1968 | 70,000 | Possibly the oldest household longitudinal surveys 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).[10] | |
| 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. | |
| Irish Longitudinal Study on Ageing (TILDA) | Cohort | Ireland | 2009 | 8,500 | Studies health, social and financial circumstances of older Irish population | |
| New Zealand Attitudes and Values Study | - | New Zealand | 2009 | n/a | - | |
| Seattle Longitudinal Study | Cohort | United States | 1956 | 6,000 [11] | - | |
| Understanding Society: The UK Household Longitudinal Study | Panel | United Kingdom | 2009 | 100,000 | Incorporates the British Household Panel Survey | |
| 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 | Cohort | United States | 1957 | 10,317 | Follows graduates from Wisconsin high schools in 1957 | |
| ONS Longitudinal Study | Panel | England and Wales | 1974 (data from 1971) | 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 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 emphasise 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 |
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See also
References
- ↑ Shadish, William R.; Cook, Thomas D.; Campbell, Donald T. (2002). Experimental and Quasi-Experimental Designs for Generalized Causal Inference (2nd ed.). Boston: Houghton Mifflin Company. p. 267. ISBN 0-395-61556-9.
- ↑ Carlson, Neil and et al. "Psychology the Science of Behavior", p. 361. Pearson Canada, United States of America
- ↑ Cherry, Kendra. "What Is Longitudinal Research?". experiments. About.com guide. Retrieved 22 February 2012.
- ↑ "What is the difference between a Panel Study and a Cohort Study?". Academia Stack Exchange. Retrieved 3 February 2016.
- ↑ Encuesta Longitudinal Colombiaba de la Universidad de los Andes - ELCA 2013
- ↑ 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.
- ↑ Favela: Longitudinal Multi-Generational Study of migrants and squatters in Rio’s Favelas, 1968-2014
- ↑ Growing Up in Scotland, Study design
- ↑ Panel Study of Belgian Households, Survey summary
- ↑ "Incidence of depression in the Stirling County Study: historical and comparative perspectives.". Psychol Med. (30(3)): 505–14. May 2000. Retrieved 23 May 2015.
- ↑ About the Seattle Longitudinal Study
External links
- ESDS Longitudinal data service
- Centre for Longitudinal Studies
- National Centre for Longitudinal Data
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