Loss and representativeness in a 53 year follow up of a national birth cohort the 1946 birth cohort
This presentation is the property of its rightful owner.
Sponsored Links
1 / 25

Dr Gita Mishra MRC National Survey of Health and Development PowerPoint PPT Presentation


  • 95 Views
  • Uploaded on
  • Presentation posted in: General

Loss and representativeness in a 53 year follow up of a national birth cohort (The 1946 Birth cohort). Dr Gita Mishra MRC National Survey of Health and Development Department of Epidemiology and Public Health Royal Free Hospital, University College Medical School, London www.nshd.mrc.ac.uk.

Download Presentation

Dr Gita Mishra MRC National Survey of Health and Development

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Loss and representativeness in a 53 year follow up of a national birth cohort the 1946 birth cohort

Loss and representativeness in a 53 year follow up of a national birth cohort (The 1946 Birth cohort)

Dr Gita Mishra

MRC National Survey of Health and Development

Department of Epidemiology and Public Health

Royal Free Hospital, University College Medical School, London

www.nshd.mrc.ac.uk


Acknowledgments

Acknowledgments

MRC NSHD Team members

Professor Michael Wadsworth (Study director)

Professor Diana Kuh

Dr Marcus Richards

Dr Rebecca Hardy

Suzie Butterworth

Stephanie Black

Rachel Cooper

Imran Shah

Warren Hilder


Benefits of the longitudinal or life course design

Benefits of the longitudinal or life course design

  • Known sequence and chronology of development and ageing, and of exposures

  • Near contemporaneous data collections

    • only short period of recall

  • Ability to describe the diversity of underlying pathways to later health outcomes


The costs of the design in a long running study

The costs of the design in a long-running study

  • The fixed sample structure

  • Each data collection is informed by contemporary scientific ideas and methods

  • Risk over time of increased sample loss and the consequent potential for bias


Mrc national survey of health and development mrc nshd

MRC National Survey of Health and Development (MRC NSHD)

Aims

Originally the study aimed to address 2 specific issues in the years before the establishment of the NHS

  • Reasons for falling fertility

  • Effectiveness of obstetrics and midwifery on premature births, infant mortality, and on promotion of health of mother’s and infants

    Has evolved into a life course study investigating

    pathways to physical and cognitive ageing


Dr gita mishra mrc national survey of health and development

MRC National Survey of Health & Development

1946 birth cohort

Birth Registrations

1 week 1946 (N=16,695)

Population of the maternity survey

1 data collection at birth (N=13,687)

Selection of follow-up sample of all single born, married women

with husbands in non-manual and agricultural employment

and 1 in 4 of all other comparable births (N=5,362)

20 data collections from age 2 to 53 years

MRC National Survey of Health & Development

1946 birth cohort

Birth Registrations

3rd - 9th March 1946 (N=16,695)

Population of the maternity survey

(N=13,687)

Selection of follow-up sample of all single born, legitimate

children of fathers in non-manual and agricultural employment

and 1 in 4 of all other single born legitimate children (N=5,362)

Study of cohort first born offspring

at ages 4 years and 8 years (N=2,205)

Study of women’s health, annually,

at ages 47-54 years (N= 1,572)

8 data collections

Study of cohort first born offspring

at ages 4 years and 8 years (N=2,205)

Study of women’s health, annually,

at ages 47-54 years (N= 1,572)


Dr gita mishra mrc national survey of health and development

Maternity study of all births in 1 week in

England, Wales & Scotland in 1946

Follow-up of a class-stratified sample (N=5362)

In infancy at 2 & 4 years

During school years at 6, 7, 8, 9, 10, 11, 13, 15 years

In early adulthood at 19, 20, 22, 23, 25, 26, 31 years

In middle adulthood at 36, 43, 53 years


Dr gita mishra mrc national survey of health and development

Costs of maternity, reason for

falling fertility

1946

Birth

1947-1950

1-4 years

Social class differences in maternal

and child mortality and morbidity.

Value of health visitors’ work.

1951-1961

6-15 years

Increasing the national level of

educational attainment. The

‘waste of talent’ problem.

1962-1976

16-30 years

Outcomes of education in terms of

occupational choice and skills.

Delinquency.

1976-

30 years onwards

Ageing processes, self care of

health, receptivity to health

promotion.

Maintaining the study’s momentum

Years

National policy problems

Cohort ages


Sources of information on sample loss

Sources of information on sample loss

By age 53 years

  • Unavoidable losses

    • Death (n=469 8.7%)

    • Emigration (n=461 8.6%)

    • Living abroad(n=119 2.2%)

  • Avoidable or potentially avoidable

    • Permanent refusal (n=640 12.4%) *only 28 new cases

    • Temporary refusal for this data collection only (first classified at age 43 y) (n=280 5.2%)

    • Failure to trace (n= 330 6.1%)


Data collections contacts with the sample n 5362

Data collections & contacts with the sample (n=5362)

CM cohort member, HV health visitor, SN school nurse, SD school doctors, T teacher, I interview,

RN research nurse, P postal


Attrition

Attrition

The greatest overall attrition occurred in early adult years (16-31 years)

  • Cohort member could, for the first time, choose whether to respond

  • 5 out of the 7 data collections were by postal questionnaire

  • Name and address changes were particularly frequent

  • There may have been an adverse effect on response due to blurring of focus of the study aims during this period


Attrition con t

Attrition con’t

The 3 later data collections (at ages 36, 43, and 53 years) have focussed strongly on health and obtained higher response rates than those earlier years

  • Clear re-focus on health

  • The employment of research nurses to collect data

  • Introduction of summary feed-back of findings with a birthday card

  • A clear explanation of the study’s aims in letters requesting each data collection


Birthday cards

Birthday cards

  • Birthday cards were introduced at age 16 years to encourage response after leaving school, which requests notification of changes of name and/or address

  • They have been continued ever since but now include details of recent work, with references to recent publications


60 th birthday

60th Birthday


Sample characteristics of avoidable losses refusals or failure to trace

Sample characteristics of avoidable losses (refusals or failure to trace)

Raised risk on avoidable loss were found in key variables

Childhood

  • Shortness at age 4 years

  • Experience of serious illness

  • Late achievement of bladder control

  • Childhood social class of crowding

  • Paternal manual social class, low cognitive test scores

  • Low parental interest in education

  • Teachers’ ratings during adolescence of frequent problems with discipline, disobedience and aggression

    Adulthood

  • Adult social circumstances of low educational attainment

  • Manual social class employment,

  • Not owning the home at 26 years

  • Not belonging to clubs or association

  • Being obese at 36 years was also associated with avoidable loss from the study at age 53 years


Attrition from avoidable causes by quartiles of educational and cognitive score at 8 years

Attrition from avoidable causes by quartiles of educational and cognitive score at 8 years


Missing data and multiple imputation

Missing data and multiple imputation

  • The importance of checking completeness is strongly emphasised at the nurse training sessions

  • 73 % of those who provided data at 53 years, were also successfully contacted on 17 or more of the 20 data collections

  • Only 7% of them had taken part in 10 or fewer previous data collections

  • Multiple imputation is now used in analysis together with sensitivity analysis to deal with missing items/contacts

    • Growth and breast cancer risks

    • Diaries of alcohol consumption


Representativeness

Representativeness

  • Representation is important not only for extrapolation, but also for estimating true prevalence, and for maintaining policy relevance

  • There are some limitations on the representativeness of this sample

    • Selection predated the major immigration flows

    • Excludes births out of wedlock

    • Excludes multiple births

  • Nevertheless it remains representative in most respects of the native population born in the early post war years


Dr gita mishra mrc national survey of health and development

Sample Representativeness: Comparison of the weighted sample at age 53 years with 1991(50-54 yrs) census data

Census

Ages 45 and up

Census

50-54 yrs

NSHD

NSHD

Census

16+ yrs


Dr gita mishra mrc national survey of health and development

Sample Representativeness: Comparison of the weighted sample at age 53 years with 1991(50-54%) census data

Males

Females


Conclusions i

Conclusions I

  • A high rate of contact can be maintained

  • Data collection with direct contact, such as home visits by a research nurse

  • Provide information about the work of the study to the study members

    • Introduction of summary feed-back of findings with the birthday card and website

    • A clear explanation of the study’s aims in a letter requesting each data collection


Conclusions ii

Conclusions II

  • The responding sample continues in most respects to be representative of the national population of a similar age

  • Consistency of response over the study’s 20 data collections has been high.

  • The size of the sample responding in adulthood is adequate for the study of the major costly diseases and for the study of functional ageing and its precursors.

  • Although the problems inherent in the prospective design are unavoidable they are not, in the study described, a barrier to scientific and policy value


References

References

Wadsworth MEJ et al. JECH 1992; 46:3000-304

Wadsworth MEJ et al. Soc Sci Med 2003; 57:2193-205

Wadsworth MEJ et al. IJE 2006; 35:49-54

Longford NT et al. JRSSA 2000; 163:381-402

De Stavola et al. AJE 2004; 159:671-682

www.nshd.mrc.ac.uk


  • Login