Growth tendencies of the “generation of independence”: the relation between socioeconomic factors and growth indices

Correspondence to: Andrej Suchomlinov, M. K. Čiurlionio 21, LT-03101 Vilnius, Lithuania. E-mail: andrej.suchomlinov@mf.vu.lt Background. The aim of the study was to evaluate the physical status of children born in 1990 in Vilnius City and Region from birth up to the end of puberty, and to investigate the epochal changes and tendencies of their growth. Materials and methods. 1 535 personal health records of children born in 1990 in Vilnius City and Region were analyzed. The main growth indices (height and weight) were recorded from birth up to the age of 18 years. The prevalence of overweight and obesity in children was found using the cut-off points for body mass index recommended by the International Obesity Task Force (Cole et al., 2000). The results of the present study were compared with the results of Lithuanian growth studies, as well as with the growth standards of the World Health Organization (WHO). Results. The prevalence of overweight and obesity in children born in 1990 in Vilnius City and Region was low: 13.60% and 2.40% in the 18-year-old boys and 9.51% and 1.90% in the 18-year-old girls, respectively. The retardation of growth was observed during the first years of independence. The main growth indices have changed in girls more than in boys: both their height (from 166.5 ± 7.0 cm to 167.9 ± 6.2 cm, during the two past decades) and their BMI (from 20.37 ± 2.27 kg/m2 to 21.28 ± 3.33 kg/m2, over the past ten years) increased. Conclusions. Certain retardation in growth of the children born in 1990 was related with the great political, social and economic transition in Lithuania. However, the retardation process was reversible. The main indices of the physical status (height, weight and body mass index) of children did not change much during the two past decades (the acceleration had stabilized). The growth patterns of the “generation of independence” by the end of adolescence showed the tendency towards a higher body weight, though the prevalence of overweight and obesity remained low.


INTRODUCTION
The most obvious changes in human physical status appear during the growth period.They include huge physical, mental and social changes.Not only human body measurements depend on the characteristics of this period, but also the health condition (since health programming proceeds) and the quality of life.For all these reasons, the human growth process and its factors are under constant investigation.
Child's growth and maturation are determined by interaction of various internal and external factors (1)(2)(3)(4)(5).Internal factors are related to inherited factors that determine the growth and maturation, while external factors are environmental conditions under which growth takes place.Though the main growth indices (height, weight and body mass index) are inherited, the environmental factors may change the growth process and even cause growth retardation.Currently, many growth factors are under exploration, the entire models of their interactions were created (6).Anyway, all growth factors may be relatively divided into different categories: ethnic, social, economic, cultural, physical and others.The interaction of the aforementioned factors is complex and not fully understood.In recent years, the studies of the growth factors gave controversial results: some authors stated that the internal factors had the bigger impact on child's growth, some argued that the impact of the external ones was greater (4,(6)(7)(8)(9).
The epochal changes of physical status are the mirror of socioeconomic conditions.Over the past century, the acceleration in height was observed worldwide.During the last decade, the acceleration in our country has stabilized, the height of children and adolescents was almost the same as 10-15 years ago.Recently, auxological data from other countries showed that stabilization in height was followed by an increase in the prevalence of overweight and obesity in children.Certain growth factors, associated with acceleration in height (for example, changes in dietary patterns), are thought to promote later disproportionate increase of body mass index (10).In recent times, the aforementioned processes emerge in Lithuania, therefore the auxological studies in our country become very important.
Besides, the world's obesity epidemic is recently spreading among children (11).However, the prevalence of overweight and obesity in Lithuania a decade ago was low in comparison with the rest of the developed world (12).Unfortunately, the experience of other countries (13)(14) has showed that the prevalence of overweight and obesity among children and adolescents in our region may start to grow in the nearest future.

MATERIALS AND METHODS
The main growth indices of children born in the 1990 in Vilnius City and Region (the "generation of independence") were investigated.The permission to conduct the study (No. 57) was received from the Lithuanian Bioethics Committee.Our study was longitudinal because we followed the growth of the same individuals from birth up to the age of eighteen years.Data were collected in 2009-2010 at three largest out-patient clinics located in Vilnius City (Antakalnio, Centro and Šeškinės) and at the Central Out-Patient Clinic of Vilnius Region (CCVR).In total, personal health records of 1 535 children were analysed.
The prevalence of overweight and obesity in child ren was found using the cut-off points as recommended by IOTF (International Obesity Task Force) (15).These cut-off points at the age of 18 years are related with the cut-off values for adult BMI (25 kg/m 2 for overweight, 30 kg/m 2 for obesity).
The data were checked to fit normal distribution.Parametric tests (t-test) were applied for comparison if data fit normal distribution.If not, nonparametric tests (Mann-Whitney) were used.

RESULTS
The body height of Lithuanian male and female newborns was 52.66 ± 2.62 cm and 52.01 ± 2.41 cm, respectively.By the end of growth (at the age of 18 years) they reached the final height of 179.72 ± 7.19 cm and 167.90 ± 6.16 cm.The body weight of Lithuanian male and female newborns was 3 578 ± 507 g and 3 449 ± 471 g, respectively.By the end of growth they reached the final weight of 71.192 ± 11.309 kg and 59.953 ± 9.752 kg.The BMI of Lithuanian male and female newborns was 12.88 ± 1.22 kg/m 2 and 12.72 ± 1.19 kg/m 2 , respectively.By the end of growth the body mass index in boys and girls reached 22.00 ± 3.21 kg/m 2 and 21.28 ± 3.33 kg/m 2 , respectively.The prevalence of overweight and obesity according to IOTF cut-off points for BMI is presented in Tables 1-2.

DISCUSSION
The results of the present study were compared with the following: 1.The results of the longitudinal study of Lithuanian infants (16).The Lithuanian children of both sexes born in 1990 were significantly taller and heavier than the newborns born in 1967-1968.Nevertheless, starting from the second or third month and up to the age of one year, the main growth indices of infants from our study became smaller (Table 3).Certain retardation in growth of the infants born in 1990 might be related with the great socioeconomic changes in Lithuania at the beginning of the period of Independence.Some macroeconomic indicators might help to visualize those changes.For example, the gross domestic product in 1990 decreased drastically and achieved the level of 1988 only in 1996 (17-18) (Fig. 1).High inflation was also registered (Fig. 2).These findings might be explained by the fact that maternal factors had an important impact on the size of the newborns (the year before 1989-1990 was the last one before huge political changes).An organism of a female from the very beginning of its growth "accumulates" the impact of various growth factors and later, during the pregnancy, transmits it to the offspring (the growth programming proceeds).Therefore, the main body size indices of the newborns reflected the growth factors of the previous generation.The mothers of the children born in 1990 were taller than the mothers of the newborns born in 1966-1967 due to the acceleration process that took place in the second half of the twentieth century in Lithuania, as well as in most other European countries.Besides, before 1990 the health care system and nutritional conditions were more or less appropriate and equal for the majority of inhabitants in Lithuania.Thus, it might be possible that women born under the stable conditions after the sixth decade of the twentieth century "transmitted" more positive growth "fund" to their children in comparison with the women born outright after (or during) the Second World War.Nowadays, when no drastic political and socioeconomic changes take place, the main body size indices of newborns are quite stable (10,(19)(20)(21).(22).The retardation in growth of the children from our survey was observed at the age of 1-4 and 7 years, that matched the curves of the main macroeconomic indicators (Fig. 1-2).The children from our study were significantly taller in comparison with the results of the cross-sectional Lithuanian growth study from 1985-1994.In some age groups (12-year-old girls) the differences in height exceeded 4 cm.Though no differences in height of the 18-year-old boys were found, certain acceleration in girls' height was observed during the first decades of independence (from 166.5 ± 7 cm to 167.9 ± 6.2 cm).

The results of the cross-sectional study of the morphological and physical status in Lithuanian children and adolescents in 1985-1994
The weight of the children did not change much either.No statistically significant differences in the boys' BMI were obtained at the age of 18 years.Nevertheless, the girls' BMI decreased significantly.Since we could not relate these changes to the insufficient nutrition, it might be explained by the impact of mass media -the pressure for extremely slim female's body as the ideal one prevailed at that time (12,23).(24).The retardation in growth of the children from our survey was observed at the age of 1-4 years; the possible factors were discussed above.There was an increase in BMI of modern girls starting from the age of 15 years (p < 0.05) which could not be explained by the different time of maturity as far as the differences remained up to the end of the growth period.BMI of 18 year-old girls from our longitudinal study (in comparison with the results of the 2000-2005 data) increased for more than 1 kg/m 2 (21.28 ± 3.33 kg/m 2 and 20.37 ± 2.27 kg/m 2 , respectively).

The cross-sectional study of the main body indices of Lithuanian children in 2000-2005
After the comparison of the results from our study and those two other Lithuanian growth studies (performed in 1985-1994 and 2000-2005), we could conclude that the growth of children during the two decades of Independence did not change much.Obviously, the acceleration in height had stabilized, the boys' BMI remained almost unchanged, though diminished BMI values in older adolescents girls from 2000-2002 study started to increase recently and almost reached the level of 1985.However, in order to clarify the aforementioned tendencies more detailed auxological studies should be performed.
4. The results of physical status in preschool children (3-6 years of age) (25).The time of adiposity rebound in our and 2003-2007 study was at the same age: in boys it happened during their seventh year of life, in girls during the sixth year.
5. The growth standards of the World Health Organization (WHO) (26)(27).Lithuanian children were taller and heavier at almost all ages (p < 0.05).There were no differences in BMI of boys starting from the age of 13 years, and in the BMI of girls starting from the age of 4 years (i.e. their body mass index did not differ much from the WHO standards for BMI).Nevertheless, due to the multiple and statistically significant differences in body height and weight, WHO growth charts seem to be inappropriate for our country.

CONCLUSIONS
Certain retardation in growth of the children born in 1990 was related to the great political, social and economic transition that happened in Lithuania in 1990-1993.However, the retardation process was reversible.The main physical indices (height, weight and body mass index) of children did not change much during the last two decades (the acceleration had stabilized).The growth patterns of the "generation of Independence" by the end of adolescence showed the tendency towards the bigger body weight, though the prevalence of overweight and obesity among Lithuanian children remained low.

Table 1 .
The prevalence of overweight and obesity among boys according to IOTF cut-off values for BMI (kg/m 2 )

Table 2 .
The prevalence of overweight and obesity among girls according to IOTF cut-off values for BMI (kg/m 2 )

off point for OW n (OW) % (OW) Cut-off point for OB n (OB) % (OB)
n -the number of children, OW -overweight, OB -obesity.