Tracking exposure to child poverty during the first 10 years of life in a Quebec birth cohort.
Seguin, Louise ; Nikiema, Beatrice ; Gauvin, Lise 等
Children growing up in poverty are at increased risk of suffering
from diverse health problems, including asthma attacks, acute
respiratory infections, growth delay, overweight and obesity as well as
mental and behavioural disorders. (1-5) Moreover, exposure to poverty
during early childhood has been associated with higher risk of almost
every adult chronic disease, (6-10) including cardiovascular diseases
(CVD) (6-8,11,12) and Alzheimer's disease, (13-17) independent of
current deprivation status. (6,7,13) Yet, we do not understand the
processes underlying these relationships. (6) Childhood poverty also
compromises children's future life opportunities and well-being by
increasing the risk of underachievement in cognitive development, social
skills, and educational attainment. (10,16,17) Given that data on
childhood poverty are usually aggregated for all children under 18
years, (18-21) we know little about trajectories of exposure to poverty
during early childhood.
Relative poverty involves a lack of minimal resources needed to
live according to a society's norms. (3,18,22-25) No single measure
can capture all dimensions of a poverty experience. (24-27) Some
multidimensional measures of poverty are available but are difficult to
interpret and remain under discussion. (25,28-31) Most poverty measures
currently used are based on income either alone, (3,23,27,32,33) as in
the Low Income Cut-off (LICO) from Statistics Canada, or in combination
with level of education and/or employment status to yield an indicator
of socio-economic status (SES). (34) Poverty is not only about lack of
material resources, yet having a low income is the basis of choice
limitations that lead to poverty and social exclusion, thus limiting
access to healthy foods, quality clothes, good housing, healthy
neighbourhoods, and quality schools. In Quebec, receiving social welfare
(SW) is an indicator of extreme poverty since this allowance represents
an income below the LICO. It is unclear whether these different measures
of poverty (below LICO, SW, and SES) operationalize the same poverty
reality. (26)
To our knowledge, there are no Canadian data on patterns and
trajectories of early childhood poverty. Given that children's
vulnerability to the deleterious effects of poverty varies according to
timing and duration of exposure, (6,13) it appears important to study
the experience of child poverty at different ages. The aim of this
article is to describe exposure to poverty of participants in a Quebec
birth cohort during the first 10 years of life according to different
measures of poverty. We also explore family characteristics associated
with different trajectories of poverty.
METHOD
Sample
The Quebec Longitudinal Study of Child Development (QLSCD) is a
birth cohort of a representative sample of Quebec singleton live births
in the period 1997-1998. The sampling methodology has been described
elsewhere. (2,35) From 2,817 selected births, 2,675 families were
contacted and 2,120 gave their consent to participate. Subjects'
baseline data were collected at 5 months of age and home interviews were
conducted annually up to the age of 8 years and every two years
thereafter, provided that subjects still resided in the Province of
Quebec. (35,36) This analysis covers data from baseline to 2008 when
participants were aged 10-11 years. The study was approved by the ethics
review boards of the Institut de la statistique du Quebec, the Centre
Hospitalier Universitaire (CHU) Sainte-Justine, and the Faculty of
Medicine of Universite de Montreal. All participants provided signed
informed consent at each round.
Definition of variables
Three indicators of poverty were examined: living in a household
with low income (below LICO), receiving social welfare (SW), and being
of low SES. Trained interviewers recorded previous 12-month household
income at each data collection occasion. (36-38) Respondents, most often
the mother, were invited to recall the sources of their past 12-month
household income. They were then asked to give their "best estimate
of the total income before taxes and deductions of all household members
from all sources". (36)
Poverty as Low Income
Low-income poverty status was defined according to the LICO
computed each year by Statistics Canada. (39) The Canadian LICO
represents an income threshold at which "families are expected to
spend 20% more [of their income] than the average family on food,
shelter, and clothing." (40) Children were classified as poor at
each data collection if they lived in a household with an annual income
before taxes below the LICO. LICO was not available for children when
they were 4 years of age because the prior data collection procedure had
occurred less than 12 months previously. (41) The Canadian LICOs take
into account size of family unit and of residential area. (40) We note
that "Although Statistics Canada does not refer to the LICO as a
measure of poverty, most academics and interested organisations regard
it as precisely that". (42)
Poverty as Living on Social Welfare
At each survey, respondents reported on their main source of income
during the previous 12 months by choosing from the following options:
salary, self-employment, employment insurance, social welfare (SW), or
other. The number of persons in the family is taken into account when
determining eligibility for and allowances provided by social welfare. A
dichotomous variable was computed to contrast families receiving SW
rather than other sources of income.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
Poverty as Being in the Lowest Socio-economic Quintile
SES was estimated at baseline and at each follow-up visit (except
at 4 years) using Willm's index of SES, which is a composite of
household income, parental educational attainment, and employment
prestige. (34,43) In two-parent families, the parent with the higher
level of income, education or occupation was used. In single-parent
families, the highest level of education or occupational status of the
responding parent was used. For each study round, the three variables
were standardized and subjected to factor analysis, which allowed for
the extraction of a single factor explaining approximately 72% of the
total variance. Factor loadings were used to compute continuous scores
of SES, truncated to range from -3 to +3. (46) For each study round, a
dichotomous indicator of low SES was computed as being ranked in the
lowest SES quintile versus other quintiles.
Duration of poverty was expressed as the number of follow-up
periods or episodes spent in a low-income family, receiving SW, or being
of low SES. Chronic poverty was defined as 3-4 episodes of poverty
during early childhood (<5 years), 3-5 episodes during middle
childhood (between 5 and 10 years), or 6-9 episodes over the entire 10
years of life.
Family Characteristics
Since there are too many missing data for fathers, we examined only
maternal characteristics at baseline: maternal educational attainment,
type of family, immigration status. European immigrant mothers were
combined with Canadian-born mothers because their characteristics are
very similar to Canadian mothers and they were too few to make a
specific category. (35,36)
Analysis
We estimated the prevalence of child poverty for each year by
dividing the number of children living in low-income households or in
families on SW during the time period of interest by the total number of
participants during the same time period. We plotted trends in the
prevalence of two poverty indicators--below LICO and SW--since the low
SES indicator always represents the lowest 20% of the population.
Children's exposure to poverty was assessed in several ways.
First, latent growth analyses were carried out among children followed
from 5 months to 10 years to identify different poverty trajectories.
The model that best fit the data was selected based on the lowest BIC
(Bayesian information criterion) value, higher entropy (>0.90), and
plausibility of interpretation.
Second, we computed the duration of poverty measured with the LICO,
receiving SW, or being of low SES during early childhood (<5 years),
during middle childhood (5-10 years), or over the entire 10 years of
life. Sampling weights were applied for cross-sectional analyses of
poverty whereas longitudinal weights were applied for longitudinal
estimations to account for attrition.
Finally, we examined family characteristics associated with
different trajectories of child poverty. Multilevel logistic regressions
for repeated measures were used to model change in the chances of
experiencing low income during the first 10 years of life as a function
of growing up in a single-parent family, the level of maternal
education, mother's immigration status, and residing in a rural or
urban area. We also examined how trajectories and duration of exposure
to low income (below LICO), SW, or low SES varied with these family
characteristics. Here, the statistical significance of between-category
differences in poverty was evaluated based on the Chi-square statistics.
RESULTS
Of the 2,120 families who provided consent in 1998, 1,334 (63%)
participated in the tenth survey in 2008 when children were aged 10-11
years. Participation in data collection declined from 96.5% at the
second to 63% at the tenth visit. Compared to those who were still
participating at age 10 years, children lost to follow-up were more
frequently living in single-parent, low-income, or SW households and
their mothers were less educated or non-European immigrants at baseline.
Trends in poverty
Figure 1 shows that almost one quarter (24.4%) of five-month-old
participating children were living in families with low income and 11.5%
of families received SW payments at that time. The prevalence of poverty
during childhood, whether measured by low income or by receipt of SW,
decreased over time and, among our participants at 10 years, 14.6% lived
in a low-income family and 2.7% were on social welfare. However, the two
curves are not parallel and at the ages of 5 and 8 years, there was a
reduction of families on SW while the number of families with a low
income was larger.
Cumulative exposure to poverty
Latent class analysis identified four plausible classes of poverty
trajectories (Figure 2): a group who always had sufficient income
(75.9%), a group with increasing likelihood of poverty (9.1%), a group
with decreasing likelihood of poverty (7.7%), and a group who always had
a low income (7.3%).
Table 1 shows there were 15.9% of children who lived chronically in
a low-income family during early childhood (<5 years) and 15.9%
during middle childhood (5-10 years). About 8% of families received SW
chronically during early childhood and 4.4% during middle childhood. The
low SES indicator covers a larger proportion of families in chronic
poverty: 22.5% of families were chronically in the lowest quintile of
the SES score during early childhood and 23.0% during middle childhood.
Over their entire 10 years of life (Figure 3), 12.2% of children lived
chronically in a low-income family, 4.6% in families receiving SW
chronically and 20.1% in families chronically in the lowest SES
quintile.
Family characteristics
Children more likely to be exposed to low income (Table 2) were
those with non-European immigrant mothers (OR=29.3, 95% CI 17.2-49.6),
with mothers with less than a high school education (OR=20.3, 95% CI
12.9-31.9), or from single-parent families (OR=12.5, 95% CI 10.4-15.2).
There is a statistically significant interaction between education and
duration of follow-up, indicating that the chances of falling into
low-income categories vary with these covariates.
However, trajectories of exposure to low income (Table 3) show that
children from chronically poor families were more likely to come from
single-parent rather than two-parent families (46.7% versus 7.0%), to
have mothers with less than a high school diploma (28.4% versus 6.7%),
and to have non-European immigrant mothers (20.4% versus 9.2%).
DISCUSSION
We examined exposure to poverty of children from the QLSCD birth
cohort from birth to 10 years old using three measures of poverty: the
low income cut-off from Statistics Canada (LICO), social welfare (SW),
and SES quintiles. We also explored family characteristics according to
different duration and trajectories of poverty. From birth until 10
years of age, there was a reduction in the proportion of children in a
family living under LICO, except at 5, 6 and 8 years of age when it
increased. This reduction was more important for families receiving SW.
Almost a quarter of children in the study experienced some periods of
poverty during those years, with 7.3% experiencing chronic poverty.
Although many families (7.7%) exited poverty during these years, there
were even more (9.1%) who entered into poverty. Given the well-known,
long-term impact of early poverty, the health of these children could be
jeopardized for the rest of their lives from this early exposure to the
deleterious living conditions associated with poverty. (6,7,13,15,45-48)
Although there was a general reduction in child poverty in the
province of Quebec from 2002 to 2006, (27,32,33,49,50) we did not see a
corresponding reduction for QLSCD children during this period. In 2003,
2004 and 2006 (i.e., at 5, 6 and 8 years of age), there was an
increasing proportion of children from this cohort who lived in a poor
family. Comparing our data with those from Quebec overall is difficult
since the latter are for children less than 18 years whereas our data
examined each age separately. Only for the year 2008, when the children
were 10 years of age, did we observe a greater reduction in the level of
child poverty, as shown in Figure 1. This reduction of the proportion of
children living in poverty might result from attrition given that each
year the participants who left the study were more likely to be the
poorest. However, the weighing of data should reduce this problem.
The three measures of poverty that we examined demonstrated similar
patterns of exposure to child poverty and showed that a high proportion
of children are exposed to poverty very early on. Many are exposed to
chronic poverty. The low SES index appears to identify a larger
proportion of chronically poor families than the LICO or the SW poverty
indicators. Interestingly, few poor families are dependent on SW, a
last-resort source of income, which implies that poverty affects a high
proportion of working families. That a higher proportion of families
stopped receiving SW compared to those coming out of a low-income status
when their child was 4 to 8 years old (Figure 1) might be due to the
return to work of mothers when their child began school. This would mean
that their income from their work was not sufficient to lift them out of
poverty. The greater reduction in the number of families with
children on SW might also result from a lower participation of these
families in the study. Again, the weighting of data should limit this
effect, and it should be noted that this greater reduction was seen only
during specific years.
Regardless of the poverty indicator examined, family
characteristics are quite similar and it appears that children of
non-European immigrant and of single-parent households are the most
susceptible to growing up in poverty conditions. A low level of maternal
education is also strongly associated with living in poverty. These are
characteristics usually observed in other studies of family poverty.
(5,15,18,51-55) Being a single parent or a newcomer in a foreign country
involves much stress, and living in poverty significantly increases the
experience of stress, which can affect parental abilities. (56-59) Poor
children can also experience stress themselves, which can be detrimental
to their health and development. (4,18,56,58-67)
During the study period (1998-2008), diverse family policies were
implemented at the Quebec and federal levels, such as a subsidized day
care program, longer parental leaves, and a child benefit program.
(27,50) However, these programs cannot explain completely the decreasing
prevalence of QLSCD child poverty. Given that children from the QLSCD
were born in 1997-98, they might not have benefitted from these new
programs as these were developped later and were oriented mostly toward
preschool children. Yet these programs probably contributed to reducing
the percentage of children living in poverty in the province.
(27,32,33,50) Other countries, such as the Scandinavian countries, have
been more successful in reducing their proportion of poor children.
Through different fiscal and social policies, their child poverty rates
ranged from 3-5% in 2007, while in Canada and Quebec in that same year,
there were still 13% of households with children under 18 years living
in poverty. (5,18,68)
Strengths and limitations
This is the first study to follow over 10 years a large group of
children from a representative sample of Quebec single births, which
allowed for defining poverty trajectories. The participation rate was
very high for the first 5 years and remained higher than or equal to
other longitudinal studies of children. (69,70) One limitation of this
study is that annual household income and its sources are self-reported.
Moreover, family income does not provide information on other potential
financial resources. Another limitation is that each year, participants
leaving the study were mainly the poorest, least educated, and
immigrants, although the weighting of data should reduce this problem.
However, despite this weighting of data, these longitudinal data are not
representative of Quebec children for this age.
CONCLUSIONS
Our study provides a unique opportunity to examine exposure to
poverty at different ages during childhood. Although it is well known
that poverty, especially during the preschool period, is associated with
higher risk of chronic diseases during adulthood, (6-11,13) this early
period of life is still affected by poverty for many children. According
to the OECD (Organisation for Economic Cooperation and Development), a
higher percentage of American and Canadian children live in poverty
compared to other age groups of the population. (68) Poverty is costly
and reducing poverty among our children must be seen as an investment in
our future. (20,21,71) Policies that focus on young children are needed
to attenuate these inequities. Future research must examine pathways and
mechanisms on how "poverty gets under the skin". There should
also be more evaluative research on effective programs and policies to
reduce child poverty permanently. To ensure the future of our children,
programs and policies that efficiently end child poverty are required.
Received: January 10, 2012
Accepted: April 26, 2012
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Louise Seguin, MD, MPH, [1-4] Beatrice Nikiema, MD, MSc, [2,4] Lise
Gauvin, PhD, [1,3-5] Marie Lambert, * MD, [6] Mai Thanh Tu, PhD, [1,2,4]
Lisa Kakinami, PhD, [7] Gilles Paradis, MD, MSc [7,8]
Author Affiliations
[1.] Department of Social and Preventive Medicine, Universite de
Montreal, Montreal, QC
[2.] Public Health Research Institute of Universite de Montreal
(PHRIUM/IRSPUM), Montreal, QC
[3.] Lea-Roback Research Centre on Social Inequalities in Health,
Montreal, QC
[4.] International Network for Research on Inequalities in Child
Health (INRICH), Montreal, QC
[5.] Research Centre of the Centre hospitalier de l'Universite
de Montreal (RCUHM/CRCHUM), Montreal, QC
[6.] Department of Paediatrics, Universite de Montreal and Centre
Hospitalier Universitaire Sainte-Justine, Montreal, QC
[7.] Department of Epidemiology, Biostatistics and Occupational
Health, McGill University, Montreal, QC
[8.] Institut national de sante publique du Quebec, Montreal, QC
* Deceased
Correspondence: Dr. Louise Seguin, Department of Social and
Preventive Medicine, Universite de Montreal, P.O. Box 6128, Montreal, QC
H3C 3J7, Tel: 514-343-7665, Fax: 514-343-5645, E-mail:
Louise.Seguin@umontreal.ca
Acknowledgements of support: This study was funded by the Canadian
Institutes of Health Research (CIHR) Grant Number 00309MOP-123079. Data
were collected by the Institut de la Statistique du Quebec, Direction
Sante Quebec. The IRSPUM and CRCHUM received infrastructure funding from
the Fonds de la Recherche en Sante du Quebec. LG holds a CIHR/CRPO
Applied Public Health Chair on Neighbourhoods, Lifestyle, and Healthy
Body Weight. GP holds a CIHR Applied Public Health Research Chair. MTT
is funded by a postdoctoral CIHR fellowship (CIHR #181755) and by a
Young Investigator Award from the Brain and Behavior Research
Foundation. These funding agencies were not involved in the study
design, data analyses, data interpretation or manuscript writing and
submission processes.
Conflict of Interest: None to declare.
Table 1. Duration of Exposure to Low Income (Below LICO ([dagger])),
Social Welfare and Low SES During Early and Middle Childhood, Among
1,121 Children Who Participated in All Study Rounds of the Quebec
Longitudinal Study of Child Development,
1998-2008
Low Income Social Welfare
n% n%
Number of study periods spent
in low economic or social
position
During early childhood 0 735 (65.5) 952 (84.9)
(before 5 years of age) 1-2 175 (15.6) 74 (6.6)
3-4 179 (15.9) 86 (7.7)
Missing 34 (3.0) 10 (0.9)
During middle childhood 0 760 (67.8) 1032 (92.1)
(5-10 years of age) 1-2 162 (14.5) 35 (3.1)
3-5 179 (15.9) 49 (4.4)
Missing 20 (1.8) 5 (0.5)
Lowest SES
Quintile
n%
Number of study periods spent
in low economic or social
position
During early childhood 0 705 (62.9)
(before 5 years of age) 1-2 152 (13.6)
3-4 252 (22.5)
Missing 12 (1.1)
During middle childhood 0 696 (62.1)
(5-10 years of age) 1-2 155 (13.8)
3-5 258 (23.0)
Missing 12 (1.1)
([dagger]) LICO = Low Income Cut-offs from Statistics Canada.
Table 2. Changes in Exposure to Low Income (Below LICO ([dagger]))
During the First 10 Years of Life According to Maternal
Characteristics at Baseline, Quebec Longitudinal Study of Child
Development, 1998-2008
Model 1
OR (95% CI)
Intercept 0.14 (0.12-0.18)
Time 0.90 (0.89-0.92)
Family type, past 12 months
Two-parent family
Single-parent family
Maternal immigration status
Canadian-born or European immigrant
Non-European immigrant
Maternal education at baseline
University
High school, vocational and trade school
< high school
Immigration status * time
High school education * time
< high school education * time
Model 2
OR (95% CI)
Intercept 0.10 (0.08-0.12)
Time 0.87 (0.85-0.88)
Family type, past 12 months
Two-parent family 1.00
Single-parent family 11.26 (9.34-13.57)
Maternal immigration status
Canadian-born or European immigrant
Non-European immigrant
Maternal education at baseline
University
High school, vocational and trade school
< high school
Immigration status * time
High school education * time
< high school education * time
Model 3
OR (95% CI)
Intercept 0.00 (0.00-0.00)
Time 0.87 (0.85-0.88)
Family type, past 12 months
Two-parent family 1.00
Single-parent family 12.47 (10.34-15.04)
Maternal immigration status
Canadian-born or European immigrant 1.00
Non-European immigrant 18.34 (10.96-30.69)
Maternal education at baseline
University 1.00
High school, vocational and trade school 4.54 (3.03-6.82)
< high school 28.00 (18.32-42.80)
Immigration status * time
High school education * time
< high school education * time
Model 4
OR (95% CI)
Intercept 0.00 (0.00-0.00)
Time 0.94 (0.87-1.00)
Family type, past 12 months
Two-parent family 1.00
Single-parent family 12.56 (10.38-15.20)
Maternal immigration status
Canadian-born or European immigrant 1.00
Non-European immigrant 29.25 (17.24-49.62)
Maternal education at baseline
University 1.00
High school, vocational and trade school 2.92 (1.90-4.49)
< high school 20.33 (12.94-31.95)
Immigration status * time 0.88 (0.84-0.94)
High school education * time 1.13 (1.09-1.17)
< high school education * time 1.09 (1.05-1.14)
([dagger]) LICO = Low Income Cut-offs from Statistics Canada.
Table 3. Trajectories of Low Income (Below LICO ([dagger])) According
to Maternal Characteristics at Baseline, Quebec Longitudinal Study of
Child Development, 1998-2008
Maternal Immigration Status
Canadian-born/ Non-European
European Immigrant
Immigrant
n (%) n (%)
Classes of poverty trajectory *
Stable non-poor 722 (70.5) 43 (44.1)
Decreasing likelihood of poverty 99 (9.7) 25 (26.0)
Increasing likelihood of poverty 85 (8.3) 5 (4.8)
Stable poor 94 (9.2) 20 (20.4)
Missing 24 (2.3) 4 (4.6)
Maternal Education Level at
Baseline
At Least No High
High School School Diploma
n (%) n (%)
Classes of poverty trajectory *
Stable non-poor 705 (74.9) 60 (33.4)
Decreasing likelihood of poverty 87 (9.3) 37 (20.6)
Increasing likelihood of poverty 65 (6.9) 24 (13.6)
Stable poor 63 (6.7) 51 (28.4)
Missing 21 (2.2) 7 (4.0)
Type of Family at Baseline
Two-parent Single-parent
n (%) n (%)
Classes of poverty trajectory *
Stable non-poor 750 (73.0) 13 (14.9)
Decreasing likelihood of poverty 106 (10.3) 17 (18.8)
Increasing likelihood of poverty 84 (8.2) 3 (3.7)
Stable poor 72 (7.0) 41 (46.7)
Missing 15 (1.5) 14 (15.8)
* p<0.001.
([dagger]) LICO = Low Income Cut-offs from Statistics Canada.
Figure 3. Duration of exposure to low income, social welfare
and low SES over the first 10 years of life, among
1121 children who participated in all study rounds,
QLSCD, 1998-2008
None 1 to 5 periods 6 to 9 periods Missing
Low income 57.1 30.5 12.2
Social
welfare 82.9 11.1 4.6
Lowest SES
quintile 54.2 24.6 20.1
Note: Table made from bar graph.
