biostudies-literaturePanagi LBeryl Alexander Charitye1926https://www.ebi.ac.uk/biostudies/studies/S-EPMC9720219biostudies-literatureUnknown31(4)<h4>Objectives</h4>To explore the impact of various measurements of long-term health conditions (LTCs) on the resulting prevalence estimates using data from a nationally representative dataset.<h4>Methods</h4>Children and young people in the Millennium Cohort Study were followed at ages 3, 5, 7, 11, and 14 years (N = 15,631). We estimated the weighted prevalence of LTCs at each time point and examined the degree to which estimates agreed with alternate health indicators (special educational needs and disability [SEND], specific chronic conditions, and common chronicity criteria) using descriptive analyses, Cohen's kappa statistic, and percentage agreement.<h4>Results</h4>The estimated weighted prevalence of LTCs peaked at 5 years old (20%). Despite high percentage agreement, we observed atInternational journal of methods in psychiatric researchThe importance of definitions in the measurement of long-term health conditions in childhood. Variations in prevalence of long-term health conditions in the UK using data from the Millennium Cohort Study, 2004-2015.PMC9720219RNAG/600Panagi LBennett SPatel SWhite SRFord TShafran RfalseThe importance of definitions in the measurement of long-term health conditions in childhood. Variations in prevalence of long-term health conditions in the UK using data from the Millennium Cohort Study, 2004-2015.<h4>Objectives</h4>To explore the impact of various measurements of long-term health conditions (LTCs) on the resulting prevalence estimates using data from a nationally representative dataset.<h4>Methods</h4>Children and young people in the Millennium Cohort Study were followed at ages 3, 5, 7, 11, and 14 years (N = 15,631). We estimated the weighted prevalence of LTCs at each time point and examined the degree to which estimates agreed with alternate health indicators (special educational needs and disability [SEND], specific chronic conditions, and common chronicity criteria) using descriptive analyses, Cohen's kappa statistic, and percentage agreement.<h4>Results</h4>The estimated weighted prevalence of LTCs peaked at 5 years old (20%). Despite high percentage agreement, we observed at2022-01-01T00:00:00Z2022 Dec2025-04-05T11:48:39.212Z2025-04-05T11:48:39.212ZS-EPMC97202193595023510.1002/mpr.1926