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Is malnutrition associated with prolonged breastfeeding?

International Journal of Epidemiology
© International Epidemiological Association 1997
Vol. 26, No. 2
Printed in Great Britain
Sir—The impact of breastfeeding beyond 12 months of
age is a topic of some controversy. Several studies from
developing countries have associated prolonged breast-
feeding with reduced food intake and malnutrition,
whereas others have found no such association.
possible association between malnutrition and prolonged
breastfeeding may be explained in several ways. Wean-
ing is a complex social and cultural process and a num-
ber of confounding factors and selection mechanisms
may explain the findings as well as some of the varia-
tions between different studies. The possibility that the
finding of a negative association between prolonged
breastfeeding and nutritional status is due to ‘reverse
causality’, i.e. that poorly growing children continue to
be breastfed, is strong.
In a recent edition of this Journal, Caulfield et al.
analyse cross-sectional data from 19 demographic sur-
veys to examine the association between breastfeeding
beyond 12 months of age and malnutrition. It is con-
cluded that there are important differences in nutritional
status associated with breastfeeding throughout the de-
veloping world and that these differences are not likely
to be due to confounding factors. Eight of the surveys
were from sub-Saharan Africa (SSA), and in five of these
datasets, still breastfed children at about 12–18 months
of age were significantly shorter and lighter than those
no longer breastfed, but the differences were largely
diminished among older children. Due to the cross-
sectional nature of the data, it was difficult to identify
the causal direction between prolonged breastfeeding
and nutritional status. The authors propose, however,
that there is a relation between child size and the deci-
sion to continue breastfeeding, i.e. ‘reverse causality’.
In SSA, the first children to be weaned are among the
tallest and the heaviest for their age; as more children
are weaned, many of them are lighter and shorter, thus
diminishing over time the difference between breastfed
and weaned children. The authors emphasize, further-
more, that longitudinal studies are needed to investi-
gate the relationship between child size and weaning
decision making.
In Guinea-Bissau, a cohort of 945 children were
followed from birth until weaning.
Only 57 (6%) of the
children were weaned before 12 months of age, and in
these cases, termination of breastfeeding was largely
associated with illness of the mother or the child, or a
new pregnancy. Thus, in Bissau, the children who were
among the first to be weaned was a highly selected
group among whom a large proportion had suffered re-
cent illness or were vulnerable in other respects. Our
results confirm that the mothers’ reasons for weaning
are an important parameter, although the direction of
the effect is ambiguous.
A longitudinal study of children above one year of
age sheds further light on the issue of prolonged breast-
In an open cohort of 849 children, we ana-
lysed weight-for-age data in children aged 18–29
months, i.e. the age range during which most children
are weaned. Throughout this age range, there was a
tendency of lower weight-for-age among breastfed
children. However, in 96 children weaned during the
study, there was no change in nutritional status
following weaning. Furthermore, children with very
low weight-for-age (i.e. ø–2.5 Z scores of the NCHS
standard) at one year of age were breastfed for a median
of 24 months compared with 22 months for children
.–2.5 Z scores (P = 0.04). In a time-to-failure analysis
of 294 children this relationship was found to be
independent of gender, maternal age, education, and
ethnic group (P = 0.02). Finally, the study suggested
that weaned children, independent of age, had higher
diarrhoeal and mortality rates. It is conceivable that a
higher mortality among weaned malnourished children
than breastfed malnourished children may result in an
additional selection, leading to more malnourished
children in the breastfed group. Such an interaction has
been observed in Bangladesh.
In a yet unpublished study of 1116 children followed
for 761 child-years we investigated the weight change
Letters to the Editor
Is Malnutrition Associated with Prolonged Breastfeeding?
Projecto de Saúde de Bandim, Bissau, Guinea Bissau, and Department
of Epidemiology Research, Danish Epidemiology Science Centre,
Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S,
following weaning. Ponderal and linear growth rates
were modelled in variance component models
for lon-
gitudinal data, adjusting for age, sex, longitudinal diar-
rhoeal prevalence prior to measurement, and seasonal
patterns. Independent of these factors, weaned children
had lower weight than breastfed children (P = 0.0002).
This effect was particularly strong in infancy where the
estimate for weaned infants was –319 g (95% confid-
ence interval [CI] –636 to –3), whereas the effect was
–137 g (95% CI : –210 to –65) and –33 g (95% CI : –112
to 45), respectively, in children aged one year and
ù2 years. The apparent contradiction with our earlier
results quoted above, suggesting lower weight in breast-
fed children, is related to the longitudinal analysis. The
random effects model enabled an assessment of the
change in weight following weaning, rather than
focusing on the difference between different weaned
and breastfed children. Weaning had no immediate ef-
fect on linear growth (P = 0.41).
The studies from Guinea-Bissau, when taken together,
suggest a slightly more complex pattern than suggested
by Caulfield et al. The data corroborate their main sug-
gestion, namely that there is a relationship between
child size and the decision—whether maternal or child-
driven—to continue breastfeeding. However, early
weaning may often be connected with illness of the
mother or the infant, and these children are not among
the heaviest, as suggested by Caulfield. Among older
children, the relation between child size and decision to
continue breastfeeding may be different: After the age
of 12 months, malnourished children are breastfed for
a long time, until the mother perceives the child as
‘healthy enough’.
Although cross-sectional data suggested that breast-
fed children were lighter than weaned children, we could
not detect any negative impact of prolonged breast-
feeding on nutritional status in a longitudinal analysis.
Rather, weaning up to the age of 24 months was
associated with a decrease in weight, in line with find-
ings from China.
The significant impact of breast-
feeding on diarrhoeal morbidity and survival suggests
that prolonged breastfeeding is essential to keep
malnourished children alive under the prevailing
conditions in most African countries south of Sahara.
Dettwyler K. Breastfeeding and weaning in Mali: cultural
context and hard data. Soc Sci Med 1987; 24: 633–44.
Victora C G, Vaughan J P, Martines J C, Barcelos L B. Is
prolonged breast-feeding associated with malnutrition.
Am J Clin Nutr 1984; 39: 307–14.
Brakohiapa L A, Yartey J, Bille A, Harrison E, Quansah E,
Armar M A et al. Does prolonged breastfeeding adversely
affect a child’s nutritional status? Lancet 1988; ii: 416–18.
Rao S, Kanade A N. Prolonged breast-feeding and malnutrition
among rural Indian children below 3 years of age. Eur J
Clin Nutr 1992; 46: 187–95.
Briend A, Wojtyniak B, Rowland M G M. Breast feeding,
nutritional state, and child survival in rural Bangladesh. Br
Med J 1988; 296: 879–82.
Cousens S, Nacro B, Curtis V et al. Prolonged breast-feeding: no
association with increased risk of clinical malnutrition in
young children in Burkina Faso. Bull World Health Organ
1993; 30: 215–22.
Taren D, Chen J. A positive association between extended
breast-feeding and nutritional status in rural Hubei
Province, People’s republic of China. Am J Clin Nutr 1993;
58: 862–67.
Caulfield L E, Bentley M, Ahmed S. Is prolonged breastfeeding
associated with malnutrition? Evidence from nineteen
demographic and health surveys. Int J Epidemiol 1996; 25:
Jakobsen M S, Sodemann M, Mølbak K, Aaby P. Reason for
termination of breastfeeding and the length of breast-
feeding. Int J Epidemiol 1996; 25: 115–21.
Mølbak K, Gottschau A, Aaby P, Højlyng N, Ingholt L, da Silva
A P J. Prolonged breast feeding, diarrhoeal disease, and
survival of children in Guinea-Bissau. Br Med J 1994; 308:
Laird N M, Ware J H. Random-effects models for longitudinal
data. Biometrics 1982; 13: 1211–31.
Inguinal Hernia Repair: Incidence of Elective and Emergency
Surgery, Readmission and Mortality
Sir—I read with great interest the article by Primatesta
and Goldacre.
This provides valuable information on
the readmissions and deaths after inguinal hernia sur-
gery, but appears to have some limitations. I do not feel
their conclusion that the lifetime risk for a male, living
to the age of 85, of having an inguinal hernia repair of
27.2% is correct. I obtained a similar figure of 26.8%,
using a cumulative incidence method, when using
National Health Service (NHS) operation data from
Avon and Somerset. This, however, is inaccurate as it
does not take into account three very important factors.
Firstly, not all inguinal hernia repairs are performed
by the NHS: In 1986 19% of all operations for inguinal
hernias were performed privately.
Did their study in-
clude private patients?
Secondly, inguinal hernias can recur after surgery. It
is unclear whether this was taken into account. Recur-
rence rates are variable. According to Hospital Episode
Statistics (HES) for NHS data in 1993, in England 7%
of all operations were for recurrent hernias.
Thirdly, a patient can have bilateral hernias (that is
one hernia on each side at the same time), or he may have
a unilateral hernia at one time and may then develop
another hernia on the other side at a later date.
Thus if they did not take into account private operations
they would have underestimated the risk of having an
inguinal hernia operation by 19% and, if they did not
consider the fact that some men have more hernias than
others, they would have overestimated the risk for indi-
vidual patients by a factor much greater than 7%.
In their discussion they state that the proportion of
cases done on a day-case basis has probably not in-
creased much since the period covered by their study
and the publication of Hospital Inpatient Enquiry. They
quoted figures of 4% for England and 6% for Oxford in
the 1979–1986 period.
However the proportion of op-
erations for inguinal hernias performed as day cases in
England was 21.7% for 1993 (the latest available fig-
ures) and for Oxford 20.9%.
It is likely that this pro-
portion will continue to increase.
Despite discussing the mortality after emergency and
elective surgery, and stating that those patients under-
going emergency surgery are probably at a higher risk
of serious illness, they conclude that elective repair of
inguinal hernia should be undertaken soon after the
diagnosis is made to minimize the risk of adverse reac-
tions. In 1977 Neuhauser examined whether elective
inguinal hernia repair in patients over 65 years of age
might increase quantity of life, by preventing the mor-
tality and morbidity associated with obstruction and
He applied current mortality rates for
elective and emergency repairs and the risk of strangu-
lation to the prevailing life expectancy of 13.3 years for
65 year old patients, he concluded that there was little
difference in quantity of life saved in choosing be-
tween immediate elective repair of the hernia and
non-operative treatment by the use of a truss. He
asserted that the choice of surgery or truss usage should
be influenced by improvements in the patient’s quality
of life and that further research was needed on this sub-
ject. Since this time the death rate has decreased mark-
edly according to OPCS figures by 29% for inguinal
hernia and by 50% for femoral hernia between 1975 and
They state that ‘the extent to which health services
are able to reduce emergency surgery, by scheduling
operations as close to the time of diagnosis as possible
may be regarded as a good indication of their perform-
ance’. Although it is desirable that patients with inguinal
hernias are treated promptly, only a small percentage of
hernias that strangulate are on the waiting list.
In the series of strangulated hernias by McEntee et al.
only 4% of patients were on the waiting list for elective
They found that the hernia strangulated in 40%
prior to the family doctor being notified, and 23% failed
to notify their doctor even after the hernia had been
present for a month. Many of the patients (24%) were
known by medical personnel to have a hernia but a
surgical consultation had not been arranged. A study in
Birmingham on patients, over the age of 65, who had
survived emergency groin hernia surgery found that
of 25 responders 20 knew they had a hernia, of these
18 (90%) had consulted their GP, but only five had been
referred for surgery.
None of the patients were actually
on the waiting list for surgery. Davies et al. in their
article on inguinal hernias and waiting lists found that
of patients presenting as emergencies, over a 2-year
period, 15% of them were actually on the waiting list.
They did, however, demonstrate that treating patients as
emergencies rather than electively has important im-
plications both financially and medically. Therefore al-
though an efficient unit may operate soon after referral,
this may have little effect on the number of emergency
operations and their morbidity and mortality.
Education of patients, general practitioners and sur-
geons is required to ensure that patients seek and re-
ceive appropriate advice for this common condition.
Primatesta P, Goldacre M J. Inguinal hernia repair: Incidence of
elective and emergency surgery, readmission and mor-
tality. Int J Epidemiol 1996; 25: 835–39.
Nicholl J P, Beeby N R, Williams B T. Role of the private sector
in elective surgery in England and Wales, 1986. Br Med J
1989; 298: 243–47.
Office of Population Census and Surveys. Hospital Episode
Statistics 1993–4. London: HMSO, 1995.
Neuhauser D. Elective inguinal herniorrhaphy versus truss in the
elderly. In: Bunker J P, Barnes B A, Mosteller F (eds).
Costs, Risks and Benefits of Surgery. New York: Oxford
University Press, 1977.
Royal College of Surgeons of England, 35–43 Lincoln’s Inn Fields,
London WC2A 3PN, UK.
Cheek C M, Williams M H, Farndon J R. Trusses in the manage-
ment of hernia today. Br J Surg 1995; 82: 611–13.
McEntee G P, O’Carroll A, Mooney B, Egan T J, Delaney P V.
Timing of strangulation in adult hernias. Br J Surg 1989;
76: 725–26.
Allen P I, Zager M, Goldman M. Elective repair of groin hernias
in the elderly. Br J Surg 1987; 74: 987.
Davies A H, Mountfield J, Armstrong C P. Inguinal hernia
waiting lists: medical and financial implications. Bristol
Med Chir J 1989; 104: 104–06.
Authors’ Response
Sir—In the calculation of lifetime risk in our study,
recurrences and bilateral inguinal hernias were taken
into account (the analysis was based on patients, not
episodes of care). As stated in our paper, only inpatients
and day cases admitted to National Health Service hos-
pitals in the Oxford region are recorded in the Oxford
record linkage study (ORLS): we therefore agree that
the lifetime risk is even higher than the figure we
We agree that patients with hernias which strangulate
are not necessarily on the waiting list. However, as
Miss Cheek says, they may nonetheless be known to
their general practitioners without having been referred
for a surgical consultation. We feel that our statement is
still appropriate that ‘each patient should undergo op-
eration when his or her risk of an adverse outcome such
as readmission, recurrence or death is as low as pos-
sible’. In a large study which reviewed hernia repairs
performed in US Army medical treatment facilities,
the authors found that patients over 60 years of age with
a complicated inguinal hernia had a 20-fold increased
risk of dying from their repair than those who under-
went elective surgery. Law and Trapnell
stated that the
benefit of a truss, when used instead of surgery, is often
overstated and suggested that a surgical opinion should
be obtained before a truss is prescribed. They examined
52 patients (median age 70) with inguinal hernia who
wore a truss. In 69% of patients the truss did not control
the hernia. It is therefore generally advisable that ingu-
inal hernias be repaired, unless there are contraindica-
tions, to reduce the possibility of complications later.
Heydorn W H, Velanovich V. A five-year U.S. Army experience
with 36,250 abdominal hernia repairs. Am Surg 1990; 56:
Law N W, Trapnell J E. Does a truss benefit a patient with
inguinal hernia? Br Med J 1992; 304: 1092.
Institute of Health Sciences, Old Road, Oxford OX3 7LF, UK.
Validity of ICD Code 410 to Identify Hospital Admission for
Myocardial Infarction
Sir—Pladevall et al.
contrast their own findings from
Corpus Christi Texas with those of five other centres,
on the sensitivity, specificity and positive and negative
predictive values of different hospital ICD discharge
codes for acute myocardial infarction validated by a
gold standard. Whilst not detracting from their own
findings, it is sad to find a discussion of this subject
published towards the end of 1996 which makes no
mention of the similar analyses published from the
numerous WHO MONICA Collaborating Centre popu-
lations over 2 years previously.
The introduction
stresses the importance of the WHO MONICA Project,
and their own Associate status, and similar diagnostic
Cardiovascular Epidemiology Unit, Ninewells Hospital and Medical
School, Dundee DD1 9SY, Scotland, UK.
criteria and they quote two sets of earlier results from
individual MONICA centres whilst stating in dis-
cussion ‘Few studies have been published in which
the validity of using ICD codes to detect MI are
The omitted comparison (Table 2
) shows that across
37 populations validated non-fatal definite myocardial
infarction had the following source ICD (8 or 9) codes:
410 averaged 91% (range 56–100%)
411 averaged 2% (range 0–11%)
412–414 averaged 4% (range 0–16%) and
Others averaged 3% (range 0–43%)
although it should be remembered that in 14 popu-
lations registration was by ‘hot pursuit’ of admissions
rather than ‘cold pursuit’ of discharges.
Conversely the MONICA ‘gold standard’ diagnostic
categories allocated to the events registered because the
hospital ICD code was 410 were:
definite myocardial infarction 74% (range 35–90%),
possible myocardial infarction 18% (range 8–60%) and
no myocardial infarction in almost all of the remainder
excepting a small number of cases classified as
ischaemic (resuscitated) cardiac arrest.
This analysis is of 28-day survivors but the ‘Special
Report’ includes a similar one for ICD codes on death
certificates in a separate table. As stated by the Corpus
Christi authors, these findings are of importance at a
time when increasing importance is attached to mon-
itoring or surveillance of acute events in coronary dis-
ease for purposes of health service management as well
as epidemiological research.
Pladevall M, Goff D C, Nichaman M Z et al. An assessment of
the validity of ICD code 410 to identify hospital
admissions for myocardial infarction: The Corpus Christi
Heart Project. Int J Epidemiol 1996; 25: 948–52.
WHO MONICA Project, prepared by Tunstall-Pedoe H,
Kuulasmaa K, Amouyel P, Arveiler D, Rajakangas A,
Pajak A. Myocardial infarction and coronary deaths in the
World Health Organization MONICA Project:– registra-
tion procedures, event rates, and case fatality rates in
38 populations from 21 countries in four continents.
Circulation 1994; 90: 583–612.
Level Curves in Lexis Diagrams
Sir—I have recently come across the note from 1992 by
Jolley and Giles
who proposed the use of level curves
(what they call ‘synoptic charts’) in (calendar time, age)
diagrams of mortality rates.
Such diagrams were studied extensively in nineteenth
century German population statistics, primarily by
and Lexis
and are well-known now-
adays as Lexis diagrams. When I used level curves in
Lexis diagrams in 1989
and 1990
I assumed that this
was an obvious and well-known representation.
Jolley D, Giles G G. Visualizing age-period-cohort trend
surfaces: A synoptic approach. Int J Epidemiol 1992; 21:
Knapp G F. Über die Ermittlung der Sterblichkeit aus den
Aufzeichnungen der Bevölkerungs-Statistik. Leipzig:
Hinrichs, 1868.
Zeuner G. Abhandlungen aus der mathematischen Statistik.
Leipzig: Felix, 1869.
Lexis W. Einleitung in die Theorie der Bevölkerungsstatistik.
Strassburg: Trübner, 1875.
Keiding N, Holst C, Green A. Retrospective estimation of
diabetes incidence from information in a prevalent popu-
lation and historical mortality. Am J Epidemiol 1989; 130:
Keiding N. Statistical inference in the Lexis diagram. Phil Trans
R Soc Lond A; 1990; 332: 487–509.
Department of Biostatistics, University of Copenhagen, Blegdomsvej 3,
DK-2200 Copenhagen N, Denmark.
... However, longitudinal results are still inconclusive. In Kenya and Guinea-Bissau, breast-feeding after 12 mo of age was associated with faster weight and length gains (7,8); in Senegal, children breast-fed during y 2 of life tended to growth faster in length (9); in Peru, a positive effect of breast-feeding on linear growth was observed in only a subset of children, aged 15 to 18 mo, whose animal-based food intake was low (4). In Sudan, continued breast-feeding beyond mo 6 of life was associated with slower length and weight gain; complementary food intake and mother's socioeconomic status were important confounders (5). ...
... Children aged 9 -18 mo who breast-fed throughout their follow-up were 3 cm longer and 370 g heavier than children breast-fed Ͻ50% of the time (7). In Kenya, children weaned at 12 mo weighed 137 g less than breast-fed children (8). ...
Full-text available
We conducted a longitudinal study among an Afro-Colombian population to investigate the influence of feeding practices and child morbidity on linear and ponderal growth during infancy. We enrolled 133 children at 5-7 mo and followed them until 18 mo. Repeated anthropometric measures were taken every 2-3 mo, with monthly interviews on feeding practices and daily self-reports on morbid conditions by the mothers of the infants. Mothers' social conditions and infants' fixed variables (gender and gestational age at birth) were measured at baseline. Growth starting points and trajectories were modeled via Hierarchical Linear Models (HLM). Children started with a mean length of 64.8 cm (95% CI: 59.8-69.7) and a mean weight of 7.68 kg (95% CI: 5.37-9.9), and gained length at a rate of 1.13-1.70 cm/mo, and weight at 66.5-319 g/mo. Breast-feeding, defined as receiving breast milk at any time within a 2-3-mo interval, was positively related to length gain (regression coefficient = 0.27 cm/mo; P = 0.04), after adjusting for social conditions and food consumption. Among mothers with low levels of education, breast-feeding had a positive effect on weight gain (regression coefficient = 0.30 kg/mo; P = 0.04); among nonbreast-fed infants, complementary food diversity generated a positive effect on weight (regression coefficient = 0.14 kg/mo; P = 0.03). Mean differences in length were related to the total proportion of healthy time (regression coefficient = 3.1; P = 0.02), whereas weight-gain rates were negatively associated with changes during illness (regression coefficient = -0.70; P = 0.04 for fever). No association was found between diarrhea episodes and infant growth. Our study confirms that breast-feeding after 6 mo of life is important for nutrition and health, likely by mitigating the negative effects of poor social conditions and diarrhea on infant growth.
... In periurban Peru, breast-feeding was associated with faster growth in length from age 12 to 15 mo in a subgroup of children but not in the entire sample (18). In periurban Guinea-Bissau, weaning was associated with a relative decrease in weight, but not length, after adjustment for age, sex, season, and the prevalence of diarrhea (19). In an urbanrural survey in Sudan, breast-fed children grew significantly slower in weight and length than did weaned children up to the age of 2 y, even after stratification for economic level and maternal literacy (15). ...
Full-text available
Prolonged breast-feeding is frequently associated with malnutrition in less-developed countries, even after adjustment for socioeconomic confounders. However, in rural Senegal, breast-feeding is prolonged when the child is stunted. We aimed to test whether the lower height-for-age of children weaned late is explained by their height before weaning or whether prolonged breast-feeding is associated with impaired growth. A cohort of 443 Senegalese children recruited from dispensaries at 2 mo of age were visited in their homes at 6-mo intervals when they were approximately 1.5 to 3 y of age. Weight, length, arm circumference, and triceps skinfold thickness were measured. Six-month increments were analyzed in relation to breast-feeding (breast-fed compared with weaned children or breast-feeding duration), season, and maternal housing with use of multiple linear regression. The mean duration of breast-feeding was 24.1 mo (quartiles 1 and 3: 21.9 and 26.4). Height-for-age at the age of 3 y was negatively associated with age at weaning (P < 0.01), but this association disappeared after adjustment for height-for-age in infancy. Length increments were significantly greater in both the second and third years of life in children breast-fed for longer durations (P < 0.05) and tended to be greater in breast-fed than in weaned children in the second year of life (P = 0.05). In the third year of life, breast-fed children had greater length increments than did weaned children in the subgroup with poor housing (P for interaction < 0.05). Growth in weight did not differ significantly according to breast-feeding. Prolonged breast-feeding improved linear growth, and the negative relation between height-for-age and duration of breast-feeding was due to reverse causality.
... This is an argument for recommending breastfeeding, also beyond infancy in populations where childhood diarrhea is common. The benefits of breast milk on child health and survival are well recognized [18], and an increased risk of persistent diarrhea in children that are not breastfed have been demonstrated previously [19]. Sequential infection may be a cause of persistent diarrhea [20] and the protective effect of breastfeeding may be through a reduction of the microbial exposure by a reduced intake of contaminated food or water and/or by immunoglobulins and other bioactive substances and essential nutrients in the breast milk. ...
Full-text available
We sought to identify predictors of extended duration of diarrhea in young children, which contributes substantially to the nearly 1 1/2 million annual diarrheal deaths globally. We followed 6-35 month old Nepalese children enrolled in the placebo-arm of a randomized controlled trial with 391 episodes of acute diarrhea from the day they were diagnosed until cessation of the episode. Using multiple logistic regression analysis, we identified independent risk factors for having diarrhea for more than 7 days after diagnosis. Infants had a 17 (95% CI 3.5, 83)-fold and toddlers (12 to 23 month olds) a 9.9 (95% CI 2.1, 47)-fold higher odds of having such illness duration compared to the older children. Not being breastfed was associated with a 9.3 (95% CI 2.4, 35.7)-fold increase in the odds for this outcome. The odds also increased with increasing stool frequency. Furthermore, having diarrhea in the monsoon season also increased the risk of prolonged illness. We found that high stool frequency, not being breastfed, young age and acquiring diarrhea in the rainy season were risk factors for prolonged diarrhea. In populations such as ours, breastfeeding may be the most important modifiable risk factor for extended duration of diarrhea.
The value of postinfancy breastfeeding for growth and nutritional status is debated. We have investigated this issue in a longitudinal study. We prospectively followed up a cohort of 264 children in western Kenya for 6 months (mean age 14 months [range 9-18] at baseline) to investigate the nature of the association between breastfeeding and growth. Only 14 (5.3%) children had been weaned at baseline, and 173 (65.5%) were still breastfed at follow-up. For analysis, children were classified into three groups of breastfeeding duration as a proportion of the total follow-up period (0-49%, n=42; 50-99%, n=49; and 100%, n=173). In general linear models multivariate analysis, children in the longest-duration breastfeeding group gained 3.4 cm (p=0.0001) and 370 g (p=0.005) more than those in the shortest duration group, and 0.6 cm (p=0.0015) and 230 g (p=0.038) more than children in the intermediate group. The strongest association between breastfeeding and linear growth was observed in households that had no latrine and daily water use of less than 10 L per person. Our findings support WHO's recommendation to continue breastfeeding for at least 2 years, especially in settings with poor sanitation and inadequate water supply.
While the benefits of breastfeeding during infancy have been well described for developing countries in terms of health and survival,'** its positive effects have been questioned for older children. From 12 to 36 months of age, the continuation of breastfeeding has frequently been associated with a low nutritional status, in terms of either weight-for-age, as in B~tswana,~ Bangladesh4 and Guinea-Bissau: height-for-age, as in Nepal,6 Senegal,7 Ghana,*" People's Republic of Congo,'o Brazil," and Uganda", or weight-f~r-height?~*~~*~~ A recent review of demographic and health surveys (DHS) found a significant, negative association between the persistance of breastfeeding and height-for-age in 5 out of 11 Sub-Saharan African countries and in 9 out of 11 countries fiom North Africa or other ~0ntinents.I~ A positive association has been decribed for a few settings only, such as China (with height-for-age and weight-for-height)" and Bangladesh (with left upper arm circumference).I6 Since the negative relationships do not seem to be explained by confounding by poverty or other factor~,g'""~ several reviews have suggested that it might be explained by "reverse causality", that is, the mother lets the
Research has not provided unequivocal support for the recommendation to continue breastfeeding until children reach at least age 24 months. In many circumstances, breastfeeding duration is chosen or conditioned by factors other than scientific evidence and recommendations. Even in communities where breastfeeding into the second year is the norm, a significant number of toddlers are weaned before the recommended age. The research reported here was conducted in a rural community of western Kenya. We prospectively followed a cohort of 264 children for 6 months (mean age at baseline, 14.1 +/- 2.4 months) to examine the effect of variable breastfeeding duration on length and weight gain. We found that breastfeeding was positively associated with growth in a manner that we inferred to be causal, the effect being stronger on linear growth than on weight gain. This was despite the fact that in a cohort where 95% were breastfeeding at baseline, the prevalence of stunting (height-for-age below -2 standard deviations of the WHO-NCHS reference) was already 48%. The present paper examines the socioeconomic characteristics, sanitation, morbidity, and complementary feeding practices that define the context of this apparently contradictory relationship. The population was poor, no household had running water, and malaria is endemic in the study area. Complementary feeding was initiated for 93% of the cohort before age 3 months. The weaning diet was bulky (77% energy from carbohydrate), and high in phytate content ([phytate]:[zinc] molar ratio, 28). Diet quality, judged by diversity and animal source food intake, was low. Several micronutrient intakes were below current recommendations, including riboflavin (63%), niacin equivalents (64%), calcium (72%), iron (74%) and zinc (33%). Based on a locally defined socioeconomic status scale, children in higher SES households were breastfed for a shorter duration than were children from poorer households. Sanitation and water consumption modified the effect of breastfeeding duration on growth: the effect was stronger in the absence of a pit latrine and at low water consumption. Our results support the recommendation to sustain breastfeeding in the second year, particularly in economically depressed environments with inadequate sanitation and water supplies.
With the increasing incidence of HIV and TB, motherless children are becoming a rapidly growing problem in Africa. However, few studies describe the survival patterns of these children. The aim of this study was to investigate the mortality of motherless children in urban and rural areas of Guinea-Bissau. A historical cohort study was set up in urban and rural areas in Guinea-Bissau. Motherless children were selected from two study cohorts under demographic surveillance since 1990. The relatives of 128 motherless children from the rural cohort and 192 from the urban area, as well as a total of 807 controls, were examined and interviewed. Controlling for significant background factors revealed that motherless children had a markedly higher mortality than that of controls in both urban (mortality rate ratio (MR) 2.32 (95% confidence interval 1.11-4.84)) and rural areas (MR = 4.16 (2.79-6.22)). Virtually all the excess mortality occurred among children under 2 y of age when their mother died. Few motherless children had been provided with surrogate breastfeeding. Since nearly all children in Guinea are breastfed until 2 y of age, premature weaning may be one of the major causes of the higher mortality rates observed among motherless children.
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The identification of myocardial infarction (MI) is typically based on finding events designated by a nosologist with the appropriate International Classification of Diseases (ICD) code, currently code 410. These codes are applied based on review of medical records or death certificates. However, other factors, including reimbursement considerations, may influence the coding process, especially for hospitalizations. Thus, the validity of using ICD code 410 to identify MI must be assessed. The Corpus Christi Heart Project (CCHP) is a population-based surveillance programme for hospitalized MI. Patients were identified using concurrent ascertainment in coronary care units and retrospective review of medical records. Events were validated as definite or possible MI using data regarding chest pain, electrocardiographic changes and cardiac enzymes. The validity of using ICD code 410 to identify cases of MI was assessed by calculating the sensitivity, specificity, predictive values and efficiency of ICD code 410 versus the CCHP 'gold standard'. Use of ICD code 410 identified 80.9% (401/496) of definite MI, but only 19.0% (243/1280) of possible MI. Only 12.3% (90/734) of discharges with an ICD 410 code received a 'no MI' designation based on the 'gold standard'. The efficiency of ICD code 410 for identifying MI was 92.0% for definite MI and 77.1% for definite and possible MI. The use of ICD code 410 to identify hospitalized cases of MI results in a modestly biased overestimate of the number of definite MI hospitalizations; however, this approach warrants consideration due to the expense of validation procedures.
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Inguinal hemia repair is one of the most common operations undertaken in routine surgical practice. It generally carries a very low risk of major adverse sequelae. We analysed profiles, separately, for elective and emergency operations to report on the incidence and major adverse outcomes of inguinal hernia repair in a geographically defined population. Age- and sex-specific hospital admission rates, emergency readmission rates within 30 days of discharge, and mortality rates, separately for elective and emergency operations, were calculated for the period 1976-1986 in the Oxford Record Linkage Study (ORLS) area. In all, 30,675 inguinal hernia repairs were performed in the area, an all-ages annual incidence of 13 per 10,000 population. Some 9% of patients underwent operation in an emergency admission. Elective operation rates remained constant over time. Emergency repairs decreased significantly over time in males. Patients who underwent emergency repair were older, had higher emergency readmission rates than those undergoing elective repair, and had significantly elevated postoperative mortality rates. In those who died it was uncommon for inguinal hernia to be recorded on their death certificates. Of the operations, 91% were undertaken on males; age-specific rates were highest in infants and the elderly; and emergency operation rates rose exponentially with age in people > 50 years. The lifetime 'risk' of inguinal hernia repair is high: at currently prevailing rates we estimate it at 27% for men and 3% for women. There is significant elevation of mortality after emergency operations. Elective repair of inguinal hernia should be undertaken soon after the diagnosis is made to minimize the risk of adverse outcomes.
The Lexis diagram is a (time, age) coordinate system, representing individual lives by line segments of unit slope, joining (time, age) of birth and death. The main theme of this paper is non-parametric continuous-time statistical analysis on the Lexis diagram, where I indicate some possible approaches within modern survival analysis. I also introduce the history of the diagram, point processes on the diagram, and the classical statistical approach based on piecewise constant intensities. The Lexis diagram is also useful for describing morbidity, and the methodology is illustrated by two Danish studies of diabetes incidence.
Background: The WHO MONICA Project is a 10-year study that monitors deaths due to coronary heart disease (CHD), acute myocardial infarction, coronary care, and risk factors in men and women aged 35 to 64 years in defined communities. This analysis of methods and results of coronary event registration in 1985 through 1987 provides data on the relation between CHD morbidity and mortality. Methods and results: Fatal and nonfatal coronary events were monitored through population-based registers. Hospital cases were found by pursuing admissions ("hot pursuit") or by retrospective analysis of discharges ("cold pursuit"). Availability of diagnostic data on identified nonfatal myocardial infarction was good. Information on fatal events (deaths occurring within 28 days) was limited and constrained in some populations by problems with access to sources such as death certificates. Age-standardized annual event rates for the main diagnostic group in men aged 35 to 64 covered a 12-fold range from 915 per 100,000 for North Karelia, Finland, to 76 per 100,000 for Beijing, China. For women, rates covered an 8.5-fold range from 256 per 100,000 for Glasgow, UK, to 30 per 100,000 for Catalonia, Spain. Twenty-eight-day case-fatality rates ranged from 37% to 81% for men (average, 48% to 49%), and from 31% to 91% for women (average, 54%). There was no significant correlation across populations for men between coronary event and case-fatality rates (r = -.04), the percentages of coronary deaths known to have occurred within 1 hour of onset (r = .08), or the percentages of known first events (r = -.23). Event and case-fatality rates for women correlated strongly with those for men in the same populations (r = .85, r = .80). Case-fatality rates for women were not consistently higher than those for men. For women, there was a significant inverse correlation between event and case-fatality rates (r = -.33, P < .05), suggesting that nonfatal events were being missed where event rates were low. Rankings based on MONICA categories of fatal events placed some middle- and low-mortality populations, such as the French, systematically higher than they would be based on official CHD mortality rates. However, rates for nonfatal myocardial infarction correlated quite well with the official mortality rates for CHD for the same populations. For men (age 35 to 64 years), approximately 1.5 (at low event rates) to 1 (at high event rates) episode of hospitalized, nonfatal, definite myocardial infarction was registered for every death due to CHD. The problem in categorizing deaths due to CHD was the large proportion of deaths with no relevant clinical or autopsy information. Unclassifiable deaths averaged 22% across the 38 populations but represented half of all registered deaths in 2 populations and a third or more of all deaths in 15 populations. Conclusions: The WHO MONICA Project, although designed to study longitudinal trends within populations, provides the opportunity for relating rates of validated CHD deaths to nonfatal myocardial infarction across populations. There are major differences between populations in nonfatal as well as fatal coronary event rates. They refute suggestions that high CHD mortality rates are associated with high case-fatality rates or a relative excess of sudden deaths. The high proportion of CHD deaths for which no diagnostic information is available is a cause for concern.
If the distribution of onset age of disease in a well-defined prevalent (crosssectional) population of patients is known, disease incidence rates specific for age and calendar time period may be estimated, assuming known mortality rates and a dosed population. This paper develops a method of estimation, illustrates this method on Danish diabetes data, and discusses tts general applicability. The prevalent population of diabetic subjects in Fyn County on July 1, 1973 was ascertained from prescriptions, and information on disease onset was obtained from the patients' medical records. In this study only patients with onset of disease before or at age 30 years were studied. The mortality of diabetic subjects in Denmark was estimated from retrospective hospttal data covering the period since 1933, and historical age-specific population sizes of Fyn County were obtained from census data. The incidence of diabetes increases wtth calendar time and with age for most cohorts. The variation with age for a fixed calendar year is more complicated, however, usually displaying a local maximum at about the age of puberty and a higher inddence at the upper end of the studied age range.
Jolley D (Cancer Epidemiology Centre, 1 Rathdowne Street, Canton South, Australia 3053) and Giles GG. Visualizing age-period-cohort trend surfaces: a synoptic approach. International Journal of Epidemiology 1992; 21: 178–182. Mortality data from 1950 to 1986 in Australia have been used to exemplify a method of displaying trends by age and cohort in populations over time. The visual summary or synoptic method Illustrated here is similar to a topographic map with age and calendar time as its ordinates. This method is complementary to conventional analyses of age-period-cohort data which lack a summary graphic view other than that provided by the trend in age-standardized rates or a three dimensional perspective plot. Mortality from ischaemic heart disease (IHD), lung cancer and motor vehicle accidents are used as examples of the method and illustrate its utility when dealing with different forms of mortality trend e.g. cross-sectional cohort, and mixed trends.
From a sample of 19,000 treatment episodes at 183 of the 193 independent hospitals with operating facilities in England and Wales that were open in 1986 it is estimated that 287,000 residents of England and Wales had elective surgery as inpatients in 1986 (an increase of 77% since 1981) and 72,000 as day cases. From 1985 Hospital In-Patient Enquiry data it was estimated that a further 36,000 similar elective inpatient treatments were undertaken in NHS pay beds (a decrease of 38%) and 21,000 as day cases. Overall, an estimated 16.7% of all residents of England and Wales who had non-abortion elective surgery as inpatients were treated in the private sector, as were 10.5% of all day cases. An estimated 28% of all total hip joint replacements were done privately, and in both the North West and South West Thames regions the proportion of inpatients treated privately for elective surgery was 31%. It is concluded that mainly for reasons of available manpower private sector activity may not be able to grow much more without arresting or reversing the growth of the NHS, in which case some method of calculating NHS resource allocation which takes account of the local strength of the private sector will be needed.