Principles of nutritional data analysis Ctown3.ppt start with planning needs research questions, dummy tables, variables and indicators analytical sequence

Principles of nutritional data analysis

Ctown3.ppt

• start with planning needs• research questions, dummy tables, variables and indicators• analytical sequence

PREQUISITES

Decide on: objectives (incl for whom) program activities that could reach objectives indicators of outcome (i.e. of objectives) and process (i.e.

of activities) coverage, intensity and targetting required to actually

meet objectives (see next) organization, institutions, finance ... iterate and negotiate until it makes sense (or doesn’t —

that must be decided too).

It’s not in principle more complicated than that; the most difficult partis deciding the content. Most planning protocols come down to this. Some try to impose a cookbook approach (like the ‘log frame’) —they don’t usually work. Better by far is to build the local capacity tofigure these things out ... help to get started ... fund crucial elements.

Coverage: how many people?

Targeting: who?

Intensity: resources/head

Content: what activities (components)?

You need to decide:

For programme planning …

Research questions …

Specify … keep going till you answer them … refer back to them when you get lost

Research question

Dummy tables

Define variables

Design questionnaire

Research questions on malnutrition:

1. How serious/extensive is it? (Compare to norms)2. Is it worse in some places/for some populations?

(Compare between groups at one time)3. Is it getting better or worse, for whom? (Compare

between times, for groups: norm 0.5 – 1 ppt/yr)4. What is cause of current situation, or changes?

(Analyze associations; includes evaluation)

You could also ask: what problems are we trying to solve, and what resources do we have … this would come in at question 1, but then continue to ask how the resources address the problems ...

1. How serious/extensive is malnutrition?

E.g. prevalences of underweight, wasting, GAM etc.

Note: interpretation may need to differ by population group, e.g. pastoralists vs agriculturalists; mortality risk varies in relation to GAM. 10% cut-point for agriculturalists may be equivalent to 20% for pastoralists

Wasting %(Cis)

Stunting %(Cis)

Oedema %

District A

E.g. of cut-points: 10% warning, 20% emergency

E.G of dummy table

2. Is malnutrition worse in some places/for some populations?

Group Wasting % Stunting % % IDPs

District A

District B

Total

Example of dummy table: compare districts A and BDon’t forget precise title!

Prevalences of wasting and stunting in children < 110 cms in Northern province, January 2007

3. Is malnutrition getting better or worse, for whom?

Example of dummy table

Group Wasting: Jan 2007

Wasting:July 2007

District A

District B

Total

Prevalences of wasting in children 6-59 months in January and July 2007 in Northern province

or

Group Under-weight 2001

Under-Weight2005

U5MR 2001

U5MR 2005

Province A Urban

Rural

Province B Urban

Rural

Total U+R

Prevalences of underweight children (6-59 mo) in 2001 (May-July) and 2005 (June-Nov)

Sources: DHS, 2001; MICS, 2005

4A. What are possible causes of the current levels of malnutrition?

Food security

Education high

Education low

Total

District A Insecure

OK

District B Insecure

OK

Prevalence of underweight in children (6-59 mo) by food security and district, controlling for education level

4B. What are possible causes of changes in malnutrition?

District A 1/07 – food insecure

7/07 – food insecure

1/07 – food secure

7/07 – food secure

With food aid

No food aid

Total

Changes in prevalences of malnutrition Jan – July 2007 in children (6-59 months) with receipt of food aid, for food insecure and secure households.

Variables and comparisons

Define dependent (outcome) and independent variables

Measures Indices Indicators

Define comparisons – are they valid? Checks? By season, sampling, age band, measurement/question?

Define population groups sampled (i.e. universe) or post-defined.

In planning, from effect size, variation, design effect, calculate needed sample size.

Now, if planning the survey, the questionnaire can be designed.

If you are using an existing dataset, you can see if the needed variables can be derived from those in it.

DATA Sources Handling – units of analysis, file structure Cleaning – errors: sources, detection, coping Transformations Language VARIABLES Anthropometric

Micronutrients

LANGUAGE

Analysis gives many shortcuts for communication, with conventions, drawings, and symbols. Use, get familiar with these, but query as we go along if they are unclear. Some conventions.

Outcome (variable) = dependent, goes on y-axis, in cells of tables, LHS of equations.

Classifying, determining (variable) = independent, goes on x-axis, defines

columns (or rows in 2-way) tables, goes on RHS of equations.

Scatterplot frequently (x-y plots of individual datapoints), draw lines from regressions. Correlations are very dependent on N, so treat with caution, but they give useful shorthand.

Regression gives more language – like residuals, interactions, and

controlling: easier with examples later.

VARIABLES

Outcome

Classifying

Determining

Process

All are interchangeable, but important to decide which is which.

Outcome variables are usually the dependent variables; content of cells in tables, LHS of equations. [NB don't usually put #s - frequencies - in cells]

Classifying variables are often area (district) or things like occupation that have no clear order. [Dummies in equations; independent variables]

Determining variables are usually expected to be associated with the dependent variable (eg education, water supply). They define columns, or are on the RHS of equations, as independent variables. They may be there as possibly causing the outcome; as getting in the way when a cause is investigated (confounding); or modifying the effect of another cause (interacting).

Process variables measure things like program delivery, coverage, access to services, etc.; can be dependent sometimes, depending on the question.

OUTCOME VARIABLES

Anthropometry - birth weight, underweight, stunting, wasting.

Micronutrient deficiencies. Iodine - eg total goitre rate in school children

Vit A - clinical signs (nightblindness, Bitot's spots, ) - serum retinol, <70 ug/l Iron - haemoglobin

CLASSIFYING VARIABLES

Area (eg district) Gender, age Occupation Distance, access ... Choose for targetting, policy argument, also interactions (eg literacy)

DETERMINING VARIABLES

Choose from those you can intervene on for programs like breastfeeding, complementary feeding, immunization, water supply, sanitation, etc But look for interactions (they can help or hinder), and confounding (which can mislead).

Common anthropometric measures.

Measures Index Cut-off & indicators Use for population assessment(see handout for emergencies’ indicators)

Birth weight Birth weight in kg. 2.5 = low bwt; % lbwt per 100 births

Predicts child growth; depends in part onmaternal health/nutrition. Trends when know vsignificant

Weight and age, 0-3yrs, 0-5 yrs.‘Pre-school children’

Weight-for-age (wt/age)as SD (z-) score w.r.t.NCHS/WHO refs

Usually<-2SDs; gives prevalenceunderweight

General summary measure, from surveys orgrowth monitoring.

Height and age,same age group asunderweight.

Height-for-age (ht/age)as SD (z-) score w.r.t.NCHS/WHO refs

Usually<-2SDs; gives prevalencestunting

Changes more slowly than underweight soavoids seasonal, current illness issues; goodcorrelate of SES and predictor of subsequentmortality; but highly correlated with wt/age sonot much better and more difficult to measure.

Weight and height,same age group

Weight-for-height(wt/ht) as SD (z-) scorew.r.t. NCHS/WHO refs

Usually<-2SDs; gives prevalencewasting<-3SDs is severe wastingand may be useful inemergencies

Mainly for screening and emergencypopulation assessment. Does not correlatewith anything much. Care: may have negativecorrelation with stunting, often due to heightmeasuring errors.

Mid-upper armcircumference(MUAC, AC), sameage group

Use measure directly,as mms.

135 mm usual roughlyequivalent to -2SDs. Othercut-offs used inemergencies.

Mainly for screening and emergencypopulation assessments. Also for surveys withlogistic constraints (eg Bangladesh MICS)

Adults: BMI, wt, ht,MUAC

Weight, height, eitherdirectly, or as BMI (wt/htsq). MUAC direct.

Women: Wt 45 kgs; ht 145cms. BMI: 18.5 mod; 16.0severe. MUAC 225 mms

Mostly research, except emergencies.

Analytical sequence (after cleaning, transforming, structuring (PANDA Chs 1 & 2))

• Situation analysis: aggregate indicators, compare with normsThen disaggregate to• One-way analyses or comparisons (PANDA Ch 3)

o by area, population group, for targetingo by potential factor for intervention, to examine associations (good/bad, high/low), for causality (or context)

• Two-way (PANDA Ch 4) for causalityo one-way factors within categories of anothero to control for possible confoundingo or to see possible effect modifications (interactions)

• Multi-way (PANDA Ch 5) for causality for more control, interactions …

Where and who:

have unmet needs for family planning services?

are sick, becoming disabled, dying prematurely?

are malnourished (and what type)?

Question Where and who: have unmet needs for family planning services? are sick, becoming disabled, dying prematurely? are malnourished (and what type)? For community-based programs and service delivery What programs and services do they have access to? reproductive health public health measures & clinical services nutrition-relevant programs What causes (and/or risk factors) are important and can be addressed through community- based programs and services? why are family planning needs unmet? causes of sickness, disability, mortality causes of malnutrition (general & micronutrient)

What supporting policies are needed for these programs to be more effective? overall: gender equity policies affecting demand and supply of family planning services equity, environment, poverty, safety nets, ... women’s education, wat/san, employment ... For macro policies What factors open to change by macro policies are important determinants of health/population/nutrition problems? as above, notably large scale long term factors such as poverty, employment, equity, social security ...

Question

Independent (classifying, determining, or intermediate) variables

Dependent (outcome) variables

Where and who: have unmet needs

for family planning services?



Classify by: admin/geographic

area socio-economic

status occupation education other similar criteria

for targeting

Outcome: demographic data: total fertility

rate (TFR), maternal mortality rate (MMR), IMR ...

contraceptive prev rate (CPR) morbidity nutrition: anthropometry +

mnutr deficiency signs summary overall: mortality

Framework for assessment and analysis (1)

Question



For community-based programs and service delivery What programs and services do they have access to? reproductive health public health measures

& clinical services nutrition-relevant

programs

Classify by: for all: women’s

education admin/geographic area socio-economic status

(SES) occupation other similar criteria

for targeting

Intermediate outcomes use of reproductive health

services clinical services, antenatal

care, immunization, wat/san ...

community-based orgns, growth monitoring systems, ...


Question Independent (classifying, determining, or intermediate) variables


What causes (and/or risk factors) are important and can be addressed through community- based programs and services? why are family

planning needs unmet?

causes of sickness, disability, mortality

causes of malnutrition (general & micronutrient)

Potential causes/determinants: examples women’s status, access to

services, knowledge attitudes practices (KAP) ...

wat/san, vectors, immunization rates ...

SES, literacy, wat/san, caring practices, access to services

Outcome: CPR, TFR, MMR, ... morbidity (esp.

Diarrhea; also ARI, malaria, HIV)

Anthropometry Examine associations of causes directly with outcome, allowing for confounding which is usually present.


Here we need associations to suggest causes to tackle ...

Assembling ...

•set of questions

•format of analyses to answer them

Question Where and who: have unmet needs for family planning services? are sick, becoming disabled, dying prematurely? are malnourished (and what type)? For community-based programs and service delivery What programs and services do they have access to? reproductive health public health measures & clinical services nutrition-relevant programs What causes (and/or risk factors) are important and can be addressed through community- based programs and services? why are family planning needs unmet? causes of sickness, disability, mortality causes of malnutrition (general & micronutrient)

Question



Where and who: have unmet needs

for family planning services?



Classify by: admin/geographic

area socio-economic

status occupation education other similar criteria

for targeting

Outcome: demographic data: total fertility

rate (TFR), maternal mortality rate (MMR), IMR ...

contraceptive prev rate (CPR) morbidity nutrition: anthropometry +


Framework for assessment and analysis for program planning in population, health and nutrition

Question Independent (classifying, determining,or intermediate) variables


Where and who: have unmet needs for family

planning services? are sick, becoming disabled,

dying prematurely? are malnourished (and what

type)?

Classify by: admin/geographic area socio-economic status occupation education other similar criteria for

targeting

Outcome: demographic data: total

fertility rate (TFR), maternalmortality rate (MMR), IMR ...

contraceptive prev rate (CPR)

morbidity nutrition: anthropometry +


For community-based programs andservice delivery

What programs and services do theyhave access to? reproductive health public health measures &

clinical services nutrition-relevant programs

Classify by: for all: women’s education admin/geographic area socio-economic status (SES) occupation other similar criteria for

targeting



care, immunization, wat/san...

community-based orgns,growth monitoring systems, ...

What causes (and/or risk factors) areimportant and can be addressedthrough community- based programsand services? why are family planning needs

unmet? causes of sickness, disability,

mortality causes of malnutrition

(general & micronutrient)

Potential causes/determinants:examples women’s status, access to

services, knowledge attitudespractices (KAP) ...

wat/san, vectors,immunization rates ...

SES, literacy, wat/san, caringpractices, access to services

Outcome: CPR, TFR, MMR, ... morbidity (esp. Diarrhea; also

ARI, malaria, HIV) Anthropometry

Examine associations of causes directlywith outcome, allowing for confoundingwhich is usually present.

What supporting policies are needed forthese programs to be more effective? overall: gender equity policies affecting demand and

supply of family planningservices

equity, environment, poverty,safety nets, ...

women’s education, wat/san,employment ...

Basic causes: equity, resources, socialexclusion ...Examine: (a) Associations of basic causes directlywith outcome, allowing for confoundingwhich is usually present.

(b) Interaction of basic causes (e.g.resources) as context with programcomponents, on outcomes; e.g.women’s status with use of services inrelation to child mortality.



For macro policies

What factors open to change by macropolicies are important determinants ofhealth/population/nutrition problems? as above, notably large scale

long term factors such aspoverty, employment, equity,social security ...

As cell above As cell above

Question Independent (classifying, determining,or intermediate) variables


Where and who: have unmet needs for family

planning services? are sick, becoming disabled,

dying prematurely? are malnourished (and what

type)?

Classify by: admin/geographic area socio-economic status occupation education other similar criteria for

targeting

Outcome: demographic data: total

fertility rate (TFR), maternalmortality rate (MMR), IMR ...

contraceptive prev rate (CPR)

morbidity nutrition: anthropometry +


For community-based programs and

What programs and services do theyhave access to? reproductive health public health measures &

clinical services nutrition-relevant programs

Classify by: for all: women’s education admin/geographic area socio-economic status (SES) occupation other similar criteria for

targeting



care, immunization, wat/san...

community-based orgns,growth monitoring systems, ...

What causes (and/or risk factors) areimportant and can be addressedthrough community- based programsand services? why are family planning needs

unmet? causes of sickness, disability,

mortality causes of malnutrition

(general & micronutrient)

Potential causes/determinants:examples women’s status, access to

services, knowledge attitudespractices (KAP) ...

wat/san, vectors,immunization rates ...

SES, literacy, wat/san, caringpractices, access to services



Examine associations of causes directlywith outcome, allowing for confoundingwhich is usually present.

What supporting policies are needed forthese programs to be more effective? overall: gender equity policies affecting demand and

supply of family planningservices

equity, environment, poverty,safety nets, ...

women’s education, wat/san,employment ...

Basic causes: equity, resources, socialexclusion ...Examine: (a) Associations of basic causes directlywith outcome, allowing for confoundingwhich is usually present.

(b) Interaction of basic causes (e.g.resources) as context with programcomponents, on outcomes; e.g.women’s status with use of services inrelation to child mortality.



For macro policies

What factors open to change by macropolicies are important determinants ofhealth/population/nutrition problems? as above, notably large scale

long term factors such aspoverty, employment, equity,social security ...

As cell above As cell above

Documents

Principles of nutritional data analysis Ctown3.ppt start with planning needs research questions, dummy tables, variables and indicators analytical sequence