Six decades of longitudinal health knowledge production: a systematic review on Nordic birth cohort studies

Figures & data

Figure 1. Flow chart of the phases of the literature search and selection³

Table 1. Characteristics of 79 Nordic birth cohort studies divided by age of enrolment.

		Number of cohort studies by age of enrollment
Characteristics		Pregnancy (n=30) or at birth (n=26), N=56	Later in life (> 1 years), N=23
Number of index children	200-499	8	1
	500-999	8	3
	1000-1999	9	7
	2000-4999	14	8
	5000-9999	9	1
	10 000-99 999	5	3
	100 000-	3	-
Types of data collected	Biological	42	16
	Clinical/physical examination	33	18
	Questionnaire	54	22
	Interview	18	14
	Psychological/psychiatric/neurological/cognitive test/evaluation	14	14
	Registers	36	15
	Environmental	8	-
Respondents on questionnaires/interviews	Mother	56	7
	Father	37	5
	Index child	19	22
	Healthcare professional	17	8
	Teacher	5	4
Exclusion/specific inclusion criteria	Non-sufficient language proficiency (excl)	22	4
	Non-sufficient health (excl)	20	1
	At risk (incl)	11	3
	Sex, Ethnicity, Age (excl)	7	5
Initial topic	General	16	4
	Specific	40	19
	Atopic diseases	13	1
	Mental/social/behavioral	6	8
	Cardiovascular diseases	-	6
	Nutrition/diet	4	-
	Diabetes I and associated immune-mediated diseases	3	-
	Microbiome	3	-
	Pre-term birth	2	2
	Pollutants	2	-
	Other (oral health, influenza A, children conceived by assisted reproductive technology, sleep)	7	2

Figure 2. Timeline of the Nordic birth cohorts.⁵

Figure 3. The number of birth cohort studies by country (in green rectangles) and approximate total number of index children recruited in them.

Figure 4. Map of the Arctic administrative areas and the Nordic birth cohorts located in the Arctic area (marked as black).⁶

Table A1. Databases included in EBSCO and ProQuest.

EBSCO	ProQuest
Academic Search Ultimate	ABI/INFORM Collection‎ (1971 - current)
America: History & Life	ABI/INFORM Dateline (1985 - current)
APA PsycArticles	ABI/INFORM Global
Arctic & Antarctic Regions	ABI/INFORM Trade & Industry (1971 - current)
Art & Architecture Complete	Accounting, Tax & Banking Collection‎ (1971 - current)
Audiobook Collection (EBSCOhost)	Applied Social Sciences Index & Abstracts (ASSIA)‎ (1987 - current)
Avery Index to Architectural Periodicals	Asian & European Business Collection‎ (1971 - current)
Business Source Ultimate	Business Market Research Collection‎ (1986 - current)
CINAHL with Full Text	Canadian Business & Current Affairs Database‎
Communication & Mass Media Complete	Coronavirus Research Database‎
eBook Academic Collection (EBSCOhost)	Criminology Collection (1975 – current)
eBook Collection (EBSCOhost)	Early English Books Online
EconLit with Full Text	Early Modern Books‎
ERIC	Ebook Central‎
GeoRef In Process	Education Collection (1966 - current)
GeoRef	Education Database‎ (1988 - current)
GreenFILE	ERIC‎ (1966 - current)
Historical Abstracts with Full Text	International Bibliography of the Social Sciences (IBSS) (1951 - current)
Library, Information Science & Technology Abstracts	Library & Information Science Abstracts (LISA)‎ (1969 - current)
MEDLINE	Library & Information Science Collection (1969 - current)
MLA Directory of Periodicals	Library Science Database‎ (1970 - current)
MLA International Bibliography	Linguistics and Language Behaviour Abstracts (LLBA)‎ (1973 - current)
OpenDissertations	Linguistics Collection (1973 - current)
Regional Business News	Linguistics Database‎
Teacher Reference Center	PAIS Index‎ (1914 - current)
	Policy File Index‎ (1990 - current)
	Political Science Database‎ (1985 - current)
	Politics Collection (1914 - current)
	Publicly Available Content Database‎
	Social Science Database information
	Social Science Premium Collection‎ (1914 - current)
	Sociological Abstracts‎ (1952 - current)
	Sociology Collection (1952 - current)
	Sociology Database‎ (1985 - current)
	Worldwide Political Science Abstracts‎ (1975 - current)

Table

Country, Code, Study name^1	Timing	Region	No. of index child-ren	Initial topic, general/specific	Retrospective/Prospective, recruitment age	Follow-ups 1. Below age of 1 2. Ages 1–6 3. 7–14 4. 15–29 5. Later					Types of data 1. Biological 2. Clinical/physical examination 3. Questionnaire/ Interviews (q/i) 4. Psychological/psychiatric/neurological/cognitive test/evaluation 5. Registers 6. Environmental						Respondents on questionnaires/interviews 1. Mother 2. Father 3. “Index child” 4. Healthcare professional 5. Teacher^2					Exclusion/specific inclusion criteria 1. Non-sufficient language proficiency (excl) 2. Non-sufficient health (excl) 3. At risk (incl) 4. Sex, Ethnicity, Age (excl)
DENMARK						1	2	3	4	5	1	2	3	4	5	6	1	2	3	4	5	1	2	3	4
D1 Copenhagen Perinatal BC	1959–	Copenhagen	9182	connections between factors early in the life, risk factors central in life and health status, General	Prospective Pregnancy	x	x			x		x	q	x	x		x		x					x
D2 The 1897, 1914 and 1936 BCs	1964–	Copenhagen County	1052	coronary heart disease, Specific	Retrospective & prospective 70, 50, 40					x	x	x	qi	x	x				x
D3 Danish Metropolitan 1953 BC	1965– 2016	Copenhagen metropolitan area	11532	intergenerational mobility and differential life-chances, Specific	Retrospective & prospective 12			x	x	x	x	x	qi	x	x		x		x	x	x				s
D4 Viborg BC	1983–1988	Viborg	1193	development of allergy, Specific	Prospective Postnatal		x				x	x	q				x	x
D5 Healthy Habits for Two (HHf2)	1984-	Odense and Aalborg	12000	health behaviour during pregnancy, General	Prospective Pregnancy	x		x	x			x	q		x		x		x
D6 Odense 1985 BC	1985–2011	Odense	276	development of asthma and allergic diseases, Specific	Prospective Postnatal	x	x	x	x		x	x	i				x	x
D7 Faroese BCs (Chef 1–5)	1986–	Tórshavn and Faroese Islands Arctic	approx.2500	effects of seafood diet and marine contaminants on growth and development, Specific	Prospective Postnatal	x	x	x	x		x	x	qi	x	x		x	x					x
D8 The Danish Foetal Origins Study 1988 (DaFO88)	1988–2009	Aarhus	965	effects of early life exposures on pregnancy outcomes, General	Prospective Pregnancy	x			x		x		qi		x		x
D9 Aarhus BC	1989–	Skejby	100000	risk factors for pre-term birth, Specific	Prospective Pregnancy	x	x				x		q		x		x					x
D10 The 1895,1905,1910 and 1915 Danish BCSs	1995–2016	Denmark	4326	health and functioning of the very old, General	Retrospective & Prospective Ages 92–100					x	x	x	i	x	x				x
D11 The Copenhagen mother-child cohort (COP1, COP2)	1996–	Cop 1: 3 hospitals, Cop2: 2 university hospitals	2988	mechanisms of human growth and reproduction, Specific	Prospective Pregnancy	x	x	x	x		x	x	q				x	x				x	x		e
D12 Danish National BC	1996–	Whole country	100000	effects of early life exposures on disease, General	Prospective Pregnancy	x	x	x	x		x		qi		x		x	x	x			x
D13 The Danish Longitudinal Survey of Children born in 1995 (DALSC)	1996–	Denmark	6011	children’s growing-up conditions in contemporary society, General	Prospective Postnatal	x	x	x	x				qi		x		x	x		x
D14 Copenhagen Prospective Studies on Asthma in Childhood COPSAC 2000	1998–2016	Greater Copenhagen area	411	gene-environment interactions in atopic diseases, Specific	Prospective Postnatal	x	x	x	x		x	x	q			x	x	x				x	x	x
D15 The DARC BCS	1998–2013	Odense	562	atopic and allergic diseases in children, Specific	Prospective Postnatal	x	x	x			x	x	i			x	x	x				x	x
D16 Ivaaq cohort	1999–2012	Nuuk, Maniitsoq, Ilulissa, Greenland Arctic	403	effects of selected exposures on pregnancy outcome and child development, General	Prospective Pregnancy	x	x	x			x		qi				x								e
D17 Copenhagen Child Cohort (CCC 2000)	2000–	Copenhagen area	6090	developmental epidemiology of mental health problems and psychopathology, Specific	Prospective Postnatal	x	x	x	x		x	x	qi	x	x		x	x	x	x	x
D18 West Jutland Cohort	2004–	County of Ringkjøbing	3681	effects of inequalities and social disparities on health and well-being, Specific	Prospective & retrospective 14–15				x	x			qi		x				x
D19 COPSAC 2010	2008–	Copenhagen	700	asthma and other wheezy disorders, eczema and allergy, Specific	Prospective Postnatal	x		x	x		x	x	qi			x	x	x					x
D20 Odense Child Cohort	2010–	Odense	2549	interaction between social, biological and environmental determinants of health, General	Prospective Pregnancy	x	x	x	x		x	x	q		x		x	x	x
D21 Adaptation to Climate Change, Environmental pollution, and Dietary Transition (ACCEPT) birth cohort	2010-	Greenland, 16 towns in North, Disko Bay, West, South and East Arctic	587	environmental exposures during pregnancy, dietary changes and health during a period of lifestyle transition and climate change. Specific	Prospective Pregnancy	x	x				x		qi				x	x		x					x
D22 Barrier dysfunction in Atopic newBorns studY (BABY)	2017–	Rigshospitalet, Copenhagen and Nordsjællands Hospital, Hillerød	450	the development of atopic dermatitis, Specific	Prospective Pregnancy	x	x				x	x	qi		x		x	x				x	x	x
FINLAND						1	2	3	4	5	1	2	3	4	5	6	1	2	3	4	5	1	2	3	4
F1 Northern Finland BC 1966 (NFBC1966)	1965–	Lappi, Kainuu, Northern Ostrobothnia regions Arctic	12231	risk factors involved in pre-term birth and intrauterine growth retardation, Specific	Prospective Pregnancy	x	x	x		x	x	x	q	x	x		x	x	x	x	x
F2 PLASTICITY – life long follow-up of cognitive ability after birth risks	1971–	Helsinki metropolitan area	1196	connection between birth risks and cognitive abilities and health, General	Prospective Postnatal		x	x	x	x	x	x	q	x	x		x		x	x			x	x
F3 Helsinki longitudinal temperament cohort	1975–2005	Helsinki	6468	infant temperament, effects of maternal subjective stress during pregnancy, Specific	Prospective Pregnancy	x	x	x					q		x		x
F4 The cardiovascular risk in young Finns Study (Laseri)	1980–	Finland, Helsinki, Kuopio, Oulu, Tampere, Turku	3596	levels of CHD risk factors and their determinants in children and adolescents, Specific	Prospective & Retrospective 3,6,9,12,15,18		x	x	x	x	x	x	q	x			x	x	x
F5 From childhood to teenage years	1981–1997	Finland, rural community in Eastern Finland	205	systolic blood pressure during childhood, Specific	Prospective, 6 months	x	x	x	x			x	q		x		x	x	x
F6 Arvo Ylppö Longitudinal Study (AYLS)	1985–2012	Uusimaa area	2193	perinatal risk factors, developmental disorders, behavioural & cognitive problems, General	Prospective Postnatal	x	x		x			x	qi	x	x		x	x		x				x
F7 Northern Finland BC 1986 (NFBC1986)	1985–	Lappi, Kainuu, Northern Ostrobothnia regions Arctic	9432	genetic, biological, social and behavioural risk factors of diseases, General	Prospective Pregnancy	x	x	x	x	x	x	x	q	x	x		x	x	x	x	x
F8 Finnish 1981 Nationwide BCS	1989–2005	Helsinki, Kuopio, Oulu, Tampere, Turku	5813	childhood mental and behavioural problems and long-term outcomes, Specific	Prospective & Retrospective Age 8			x	x				qi		x		x	x	x		x	x
F9 Diabetes Prediction and Prevention Project (DIPP)	1994–2011	Turku, Oulu, Tampere	17000	prenatal and childhood diet, connection to type 1 diabetes, allergies, asthma, obesity, Specific	Prospective Postnatal	x	x	x	x		x		qi		x		x	x					x	x
F10 Helsinki BCS 1934–44, 1924–1933, (Idefix)	1995–	Helsinki	15846	importance of early life factors on later health outcomes, General	Retrospective & prospective 51–71					x	x	x	q		x				x
F11 Glycyrrhizin in Liquorice (GLAKU) cohort	1998–	Helsinki	1049	effects of maternal liquorice consumption on developmental outcomes of offspring, Specific	Prospective Postnatal	x		x	x		x	x	q	x	x		x		x				x		e
F12 Development and Functioning of Very Low Birthweight Infants from Infancy to School Age (PIPARI)	2001–	Turku	478	effects of foetal risk factors on long-term outcome, neonatal intensive care outcome, General	Prospective Postnatal	x	x	x	x		x	x	q	x			x	x	x	x		x	x	x
F13 Helsinki studies of very low birth weight adults	2004–	Finland, Uusimaa	338	how being born preterm at very low birth weight affects adult health and well-being, Specific	Prospective & retrospective, 19–26				x	x	x	x	q	x					x					x
F14 Steps to the Healthy Development and Well-being of Children (STEPS) Study	2007–	Southwest Finland hospital district	1827	early development, health and well-being of children, effects later in life, General	Prospective Pregnancy	x	x	x			x	x	q	x	x		x	x			x	x	x
F15 Preterm Birth, Pregnancy and Offspring Health in Adult Life (ESTER)	2009–	Lappi, Kainuu, Northern Ostrobothnia areas Arctic	779	effects of preterm birth, maternal hyper-tension, and gestational diabetes, Specific	Retrospective & prospective 20–24				x		x	x	q		x				x				x	x
F16 CHILD SLEEP BC	2011–2015	Tampere	1673	sleep in families with newborn children, Specific	Prospective Pregnancy	x	x				x		q		x		x	x				x
F17 FinnBrain BCS	2011–	Turku & Åland Islands	3837	effects of early life stress (including prenatal) on child brain development, Specific	Prospective Pregnancy	x	x	x			x	x	q	x	x		x	x	x	x		x	x
F18 Kuopio BC (KuBiCo)	2012–	Kuopio	10 000	effects of genetics, epigenetics, and risk factors during pregnancy on the somatic and psychological health status of the mother and the child, General	Prospective Pregnancy	x	x	x			x		q		x	x	x
F19 Infants born at the Central Finland Central Hospital	2014–2018	Finland, Central Finland	212	foetal microbiome, association with colic and atopic manifestations, Specific	Prospective, Pregnancy	x	x				x		q		x		x			x			x
F20 Health and Early Life Microbia (HELMI)	2016–	Helsinki region	1055	intestinal microbiota development, lifestyle, environmental, and genetic factors, Specific	Prospective Pregnancy	x	x				x		q	x	x	x	x	x		x		x	x
NORWAY						1	2	3	4	5	1	2	3	4	5	6	1	2	3	4	5	1	2	3	4
N1 Bergen 1940 BC	1970–1992	Bergen	1331	conditions of work-insufficiency, medical, psychological, educational, Specific	Retrospective & prospective 30			x	x	x		x	qi	x	x				x	x				x
N2 Nord‐Trøndelag 1973, 1983, 1994, 2006 cohorts	1973–2006	Nord- Trøndelag	1800	oral health, connection with social status, Specific	Prospective & Retrospective 13–14, 35–44			x	x	x		x	q						x	x
N3 Patterns of sugar consumption in early childhood	1979-	Farming town	231	sugar consumption and dietary habits, Specific	Prospective Pregnancy	x	x	x					qi				x			x
N4 Environment and Childhood Asthma birth cohort study (ECA)	1992–2009	Oslo	3754	air pollution in relation to asthma in young children, Specific	Prospective Postnatal	x	x	x	x		x	x	qi			x	x	x				x	x
N5 Norwegian Mother, Father and Child Cohort Study (MoBa)	1999–	Whole country	114000	aetiology of complex diseases, exposures and lifestyles during pregnancy, General	Prospective Pregnancy	x	x	x			x	x	q		x		x	x	x	x		x
N6 Environmental causes of type 1 diabetes (MIDIA)	2001–	Whole country	900	environmental causes of type 1 diabetes, Specific	Prospective Postnatal	x	x	x	x		x	x	q				x	x					x	x	e
N7 Human Milk Study (HUMIS)	2002–	Whole country	2606	organic pollutants in mothers’ milk, exposure factors and health outcomes, Specific	Prospective Postnatal	x	x	x			x		q		x		x					x
N8 Norwegian Microbiota Cohort (NoMIC)	2002–	Southern Norway	601	gut microbiota development, composition in connection to health, Specific	Prospective Postnatal	x	x	x			x	x	qi				x		x			x
N9 The Trondheim Early Secure Study (TESS)	2007–	Trondheim	1250	mental health, psychosocial development, weight, and health related behaviour, Specific	Prospective & Retrospective 4		x	x			x	x	qi	x	x		x	x	x	x	x	x
N10 Akershus Birth Cohort Study ABC	2008–2013	Akerhus	3752	postpartum mental health, Specific	Prospective Pregnancy	x	x						q		x		x					x
N11 The Norwegian Influenza Pregnancy Cohort (NorFlu)	2010-	Oslo, Bergen	4500	consequences of influenza A (H1N1) during pregnancy, Specific	Prospective Pregnancy	x	x	x			x	x	q	x	x		x			x	x			x
N12 The Akershus Cardiac Examination ACE 1950 study	2011-	Akerhus	3706	the development and progression of cardiovascular and cerebrovascular disease (CVD/CeVD), Specific	Prospective & retrospective 63–65					x	x	x	qi	x					x
SWEDEN						1	2	3	4	5	1	2	3	4	5	6	1	2	3	4	5	1	2	3	4
S1 The study of men born in 1913 and 1943	1963–2014	Gothenburg	1653	risk factors for cardiovascular disease (CVD) among men, Specific	Prospective & Retrospective 50					x	x	x	qi		x				x						s
S2 Stockholm metropolitan study (1953 cohort)	1963–1986	Stockholm Metropolitan area	13476	intergenerational mobility, deviance, marital adjustment, Specific	Prospective & Retrospective 12/13			x	x	x			q/ i	x	x		x		x			x
S3 The Helsingborg Birth Cohort (HbgBC)	1964–	Helsingborg	4091	future health of mothers and offspring, effects of smoking, Specific	Prospective Pregnancy	x			x	x		x	q		x		x		x	x
S4 The Prospective Population Study on Women in Gothenburg (PPSW)	1968–2011	Gothenburg	1462	CVDs, diabetes, cancer, dementia, mental illness in middle aged women, Specific	Prospective & Retrospective 38, 46, 50, 60					x		x	qi	x	x				x	x					s
S5 Growing up in Uppsala	1969–1983	Uppsala	1715	role of public services in identification and treatment of health and adjustment problems, Specific	Prospective & Retrospective 4		x	x	x			x	qi	x	x		x	x		x	x
S6 Uppsala Longitudinal study of adult men (ULSAM)	1970-	Uppsala	2322	identifying metabolic risk factors for cardiovascular disease, Specific	Prospective & retrospective, 50					x	x	x	qi	x					x						s
S7 Gothenburg H70 study	1971–	Gothenburg	4853	normal ageing processes, social and medical conditions, General	Prospective & Retrospective 70					x	x	x	qi	x	x				x	x		x
S8 Swedish asthma and allergy birth cohort	1974–2007	Linköping county	1701	development of asthma and allergic diseases, Specific	Prospective Postnatal		x	x		x			qi		x		x	x	x
S9 The coronary risk factor study in southern Sweden (CRISS)	1990–1997	Helsingborg	991	coronary risk factors among middle aged men, Specific	Prospective & Retrospective 37					x	x	x	q						x						s
S10 Children, Allergy, Milieu, Stockholm, Epidemiology study (BAMSE)	1994–	Stockholm	4089	risk factors for asthma, allergic diseases and lung function, Specific	Prospective Postnatal		x	x	x		x	x	q		x		x	x	x			x	x
S11 South East Sweden BCS (SESBiC)	1995–2009	Hässleholm, Western Blekinge	1723	children’s mental development, risk, resilience, psychosocially burdened families, Specific	Prospective Postnatal		x	x					q		x		x		x
S12 Paediatric Allergy Study (The BAS cohort)	1996–2010	Jämtland	1231	development of allergy during childhood, Specific	Prospective Postnatal		x	x			x		q				x	x
S13 N5 Gotland 1989 birth cohort	1996–	Isle of Gotland	707	respiratory allergy, eczema and atopic sensitisation, Specific	Retrospective & prospective 7–8			x			x		q				x	x	x
S14 All Babies in Southeast Sweden (ABIS)	1997–	Southeast Sweden	17055	diabetes type 1, immune-mediated diseases (allergy, asthma, IBD, coeliac disease, cancer, etc., Specific	Prospective Postnatal		x	x			x		q		x		x	x	x
S15 Diabetes Prediction in Skåne (DiPiS)	2000–2019	Skåne	3868	genetic and immunologic markers predicting type I diabetes, and associated immune mediated diseases, Specific	Prospective Postnatal	x	x	x	x		x	x	q				x	x						x
S16 Good ageing in Skåne (GÅS-SNAC)	2003–	Skåne	4500	health, illness, functional capability, social situation and care need among elderly, General	Prospective & retrospective 60					x	x	x	q	x					x	x
S17 Infants of Western Sweden	2003–	Western Sweden	8176	risk factors for sudden infant death syndrome, asthma, allergic diseases, Specific	Prospective Postnatal	x	x						q		x		x	x
S18 Assessment of Lifestyle and Allergic Disease During Infancy (ALADDIN)	2004–2016	Järna and Stockholm	552	effects of environmental and lifestyle factors during pregnancy on allergies, Specific	Prospective Pregnancy	x	x				x	x	qi			x	x	x					x
S19 Halland Health and Growth Study (H^2GS)	2007–2013	Halland	2666	child health and growth from parental perspective and needs, Specific	Prospective Postnatal	x	x					x	q				x	x
S20 The Swedish Environmental Longitudinal, Mother and child, Asthma and allergy (SELMA) study	2007–2015	Värmland county	2582	asthma and allergy, endocrine disrupting chemicals, early life exposures, Specific	Prospective Pregnancy	x	x				x		q			x	x			x		x	x
S21 Biology, Affect, Stress, Imaging and Cognition (BASIC) cohort	2009–	Uppsala	5492	bio-psychological aetiological processes of perinatal depression (PND), Specific	Prospective Pregnancy	x	x				x	x	q	x	x		x			x		x	x		a
S22 The Uppsala-Stockholm Assisted Reproductive Techniques Study (UppStART)	2011–	Greater Uppsala and Stockholm municipalities	514^9	epigenetic alterations in ART conceived children; lifestyle factors in connection to pregnancy outcomes, Specific	Prospective Pregnancy	x					x		q		x		x	x				x		x
S23 Nutritional impact on Immunological maturation during Childhood in relation to the Environment (NICE)	2014–	Luleå Arctic	655	immunological maturation and allergy development, environmental exposures, Specific	Prospective Pregnancy	x	x				x	x	q				x	x				x
S24 NothPop	2016–	Västerbotten	10 000	lifestyle-related diseases and behaviours, General	Prospective Pregnancy	x	x	x			x		q		x		x	x				x			a
ICELAND						1	2	3	4	5	1	2	3	4	5	6	1	2	3	4	5	1	2	3	4
I1 LIFECOURSE study	2016–2020	Whole country	2378	influence of stress on harmful behavioural outcomes among adolescents, Specific	Retrospective & prospective 12/13			x			x		q		x				x

¹We have listed main references (e.g. article, cohort webpage) of each cohort to a Appendix 3.

²Column “Respondents on questionnaires/interviews” refers to participants who responded to the questionnaires/surveys in order to illustrate who the active respondents were in contrast to, for instance, routinely collected anthropometric measures, such as height and weight.

³Uppstart participants were adult couples.

Table

Section and Topic	Item #	Checklist item	Reported (Yes/No)
TITLE
Title	1	Identify the report as a systematic review.	Yes
BACKGROUND
Objectives	2	Provide an explicit statement of the main objective(s) or question(s) the review addresses.	Yes
METHODS
Eligibility criteria	3	Specify the inclusion and exclusion criteria for the review.	No
Information sources	4	Specify the information sources (e.g. databases, registers) used to identify studies and the date when each was last searched.	No
Risk of bias	5	Specify the methods used to assess risk of bias in the included studies.	NA
Synthesis of results	6	Specify the methods used to present and synthesise results.	No
RESULTS
Included studies	7	Give the total number of included studies and participants and summarise relevant characteristics of studies.	Yes
Synthesis of results	8	Present results for main outcomes, preferably indicating the number of included studies and participants for each. If meta-analysis was done, report the summary estimate and confidence/credible interval. If comparing groups, indicate the direction of the effect (i.e. which group is favoured).	Yes
DISCUSSION
Limitations of evidence	9	Provide a brief summary of the limitations of the evidence included in the review (e.g. study risk of bias, inconsistency and imprecision).	No
Interpretation	10	Provide a general interpretation of the results and important implications.	Yes
OTHER
Funding	11	Specify the primary source of funding for the review.	No (in abstract)
Registration	12	Provide the register name and registration number.	NA

From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71. doi: 10.1136/bmj.n71

For more information, visit: http://www.prisma-statement.org/

Table

Section and Topic	Item #	Checklist item	Location where item is reported
TITLE
Title	1	Identify the report as a systematic review.	pg 1
ABSTRACT
Abstract	2	See the PRISMA 2020 for Abstracts checklist.
INTRODUCTION
Rationale	3	Describe the rationale for the review in the context of existing knowledge.	pg 2–3
Objectives	4	Provide an explicit statement of the objective(s) or question(s) the review addresses.	pg 3
METHODS
Eligibility criteria	5	Specify the inclusion and exclusion criteria for the review and how studies were grouped for the syntheses.	pg 3
Information sources	6	Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted.	pg 3–4 and Appendix 1
Search strategy	7	Present the full search strategies for all databases, registers and websites, including any filters and limits used.	Appendix 1
Selection process	8	Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process.	pg 3–4
Data collection process	9	Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process.	pg 3–4
Data items	10a	List and define all outcomes for which data were sought. Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect.	pg 4
	10b	List and define all other variables for which data were sought (e.g. participant and intervention characteristics, funding sources). Describe any assumptions made about any missing or unclear information.	pg 3–4
Study risk of bias assessment	11	Specify the methods used to assess risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.	NA
Effect measures	12	Specify for each outcome the effect measure(s) (e.g. risk ratio, mean difference) used in the synthesis or presentation of results.	NA
Synthesis methods	13a	Describe the processes used to decide which studies were eligible for each synthesis (e.g. tabulating the study intervention characteristics and comparing against the planned groups for each synthesis (item #5)).	NA
	13b	Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions.	NA
	13c	Describe any methods used to tabulate or visually display results of individual studies and syntheses.	NA
	13d	Describe any methods used to synthesise results and provide a rationale for the choice(s). If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.	NA
	13e	Describe any methods used to explore possible causes of heterogeneity among study results (e.g. subgroup analysis, meta-regression).	NA
	13f	Describe any sensitivity analyses conducted to assess robustness of the synthesised results.	NA
Reporting bias assessment	14	Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases).	NA
Certainty assessment	15	Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome.	NA
RESULTS
Study selection	16a	Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.	pg 4, Figure 1
	16b	Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded.	Not possible due to space limitations
Study characteristics	17	Cite each included study and present its characteristics.	Appendix 2
Risk of bias in studies	18	Present assessments of risk of bias for each included study.	NA
Results of individual studies	19	For all outcomes, present, for each study: (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e.g. confidence/credible interval), ideally using structured tables or plots.	NA
Results of syntheses	20a	For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies.	NA
	20b	Present results of all statistical syntheses conducted. If meta-analysis was done, present for each the summary estimate and its precision (e.g. confidence/credible interval) and measures of statistical heterogeneity. If comparing groups, describe the direction of the effect.	NA
	20c	Present results of all investigations of possible causes of heterogeneity among study results.	NA
	20d	Present results of all sensitivity analyses conducted to assess the robustness of the synthesised results.	NA
Reporting biases	21	Present assessments of risk of bias due to missing results (arising from reporting biases) for each synthesis assessed.	NA
Certainty of evidence	22	Present assessments of certainty (or confidence) in the body of evidence for each outcome assessed.	NA
DISCUSSION
Discussion	23a	Provide a general interpretation of the results in the context of other evidence.	pg 10–13
	23b	Discuss any limitations of the evidence included in the review.	pg 12
	23c	Discuss any limitations of the review processes used.	pg 12
	23d	Discuss implications of the results for practice, policy, and future research.	pg 12–13
OTHER INFORMATION
Registration and protocol	24a	Provide registration information for the review, including register name and registration number, or state that the review was not registered.	Appendix 1
	24b	Indicate where the review protocol can be accessed, or state that a protocol was not prepared.	Appendix 1
	24c	Describe and explain any amendments to information provided at registration or in the protocol.	NA
Support	25	Describe sources of financial or non-financial support for the review, and the role of the funders or sponsors in the review.	pg 13
Competing interests	26	Declare any competing interests of review authors.	pg 13
Availability of data, code and other materials	27	Report which of the following are publicly available and where they can be found: template data collection forms; data extracted from included studies; data used for all analyses; analytic code; any other materials used in the review.	Appendix 1

From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71. doi: 10.1136/bmj.n71