Biological age of the child

Each child has an individual rate of biological development, and his biological age may differ to a certain extent from the age of his peers on the birth certificate. We are talking about the individual biological clock of the organism, which have a specificity in speed. This is so important an individual characteristic that even such powerful external synchronizers as the Sun, the Moon, the change of seasons, the change of day and night are incapable of neutralizing it and subordinating it to the general rhythm of the current of time. Many indicators of the functional capabilities of the organism, its reactivity systems correlate primarily with biological age, but not with the calendar. Features of the biological age of the child are important for the adoption of an individual mode of life, health protection, the use of different approaches to his upbringing and learning. It is difficult to put on one desk and make the same demands for two friends of 6 years of age (according to the calendar), if the biological age of one of them is 4, and the second one is 8 years old. And this is often found in our schools.

Therefore, in the biology of childhood, attempts have been made to classify periods of childhood, not according to the calendar life span, but on the essential biological features of maturity. The periodizations of prof. IA Arshavsky and G. Grimm.

IA Arshavsky's classification for the postnatal period of life

1. The neonatal stage of development is from birth to the end of feeding with milk.
2. The period of lactotrophic nutrition - before the introduction of thick complementary foods.
3. The period of combination of dairy nutrition and complementary foods - until the realization of the posture of standing.
4. Preschool age - development of locomotion acts. Formation of walking and running.
5. Preschool age - before the appearance of the first permanent teeth.
6. Junior school - until the first signs of puberty.
7. Senior school - until the end of puberty.

An interesting point of the classification is to emphasize the connection between developmental biology and the type of nutrition. In this case, not always the association is determined by the degree of maturity of the child. It can be created arbitrarily. There is also a clear tendency to determine the essence of the period, and not the criteria for its isolation.

Classification by G. Grimm

1. The neonatal period is until the healing of the umbilical wound.
2. Breast age - before the appearance of the first milk tooth.
3. Nursery age - before mastering walking.
4. Preschool age - before the appearance of the first permanent tooth or the end of the first stretching.
5. Junior school age - to the first sign of puberty.
6. The senior school age is until the end of puberty.
7. The period of youth or maidenhood is until the optimum performance is reached.

This classification is much more focused on the delimiting criteria of biological age periods. The disadvantage is the relative rudeness of division with excessively large age blocks.

The variant of biological periodization can be and such:

1. Pre-neonatal period (for premature or small) - up to a body weight of 2500 g and the formation of stable swallowing and sucking reflexes.
2. The neonatal period is before the removal of the physiological hypertension of the flexors of the upper limbs.
3. Early infancy - until complete removal of the physiological hypertension of the flexor of the extremities.
4. Late breast age - to walk without support and support.
5. Breastfeeding - until the full eruption of milk teeth.
6. Pre-school - up to the obvious signs of the second period of milk bite (diastema - tremes).
7. Preschool age - before the formation of a positive Philippine test.
8. Junior school age, or pre-pubertal, - until the appearance of secondary signs of puberty.
9. The pubertal first (I-II stage of maturation according to J. Tanner).
10. The pubertal second (stage III-IV maturation by J. Tanner).
11. The pubertal third (V stage of maturation according to J. Tanner).
12. Age of maturity - from the completion of transverse growth (according to the measurement of bitrochamber and biacromial distances).

To determine the biological age of a child, an evaluation is used of the development of such traits that reflect new qualitative signs during the biological maturation process or have a high degree of correlation with biological maturation. The simplest markers of biological age in adolescent children may be signs or stages of puberty. In young children, the biological age can be judged by the development and disappearance of the basic reflexes of newborns, the formation of motor skills, the appearance of milk teeth. In the preschool age, the appearance of permanent teeth is an important sign of maturity. In special studies, the biological age is determined radiologically, according to the number of available points and ossification nuclei. It is wrong to believe that bone age is the reflection of the true biological age of a child's body. This is the age of the bone system, depending on the combination of factors or conditions of development of the musculoskeletal system. The remaining physiological systems can develop at a different pace and have other age characteristics.

Convenient guidelines for tracing the biological age can be the evolution of hemoglobins of peripheral blood, the cytometric formula of lymphocytes, the formation of the a-rhythm of the electroencephalogram, etc. All the anthropometric, physiological, metabolic, immunological signs of a healthy child, having a clear and sufficiently vivid age dynamics or functional evolution, can be used to judge the biological age relative to the age of the calendar. For this, it is necessary to have tables of age distributions of these characteristics, preferably presented in a centile or nonparametric form. The biological age of the examinee for this system (bone, cardiovascular, blood system, kidney tubule function, etc.) will most likely correspond to the calendar age period when the quantitative or dimensional characteristic of the organ (function) obtained falls within the interval between 25 and 75th centile distribution. This indicates the most typical characteristics or properties inherent in 50% of healthy children of the age-sexual group. In the absence of tables of distributions on biological age, it can be tentatively judged on the basis of the maximum approximation of the chosen quantitative characteristic to one of the average age values (arithmetic mean, median or mode).

The biological age of a child can be said with certainty only if, for a number of signs of maturity, it reveals similar trends in magnitude and direction. Thus, the biological age of the child is the dominance of certain biological ages of individual tissues, organs and systems of the body. It can be represented in the form of the most frequent age or average biological age and some description of the revealed oscillations. This is the basis for judging the degree of harmony or disharmony in the growth and maturation of a child, or, in the language of theoretical biology, about the degree of heterochrony of development.

Heterochrony is inherent to every child, it is an inalienable property of the development process. The pronounced disharmonization with retardation of development (retardation, or bradigenesis) of some systems or advance of development (acceleration, or tachygenez) of others creates critical states of functional adaptation and vital activity with an increased risk of diseases.

Of the anthropometric features most closely correlated with biological age, you can indicate the body weight, the circumference of the chest, the ratio of the upper and lower segments of the body. A set of characteristics that can be used to determine biological age is given in the chapter on physical development.

Very informative and valuable for the practice of pediatricians, the biological age diagnostics method is its integral evaluation for a large set of different and age-specific characteristics associated with different physiological systems. Such an approach has proved itself in perinatology, when there are significant differences between the terms of gestation, anthropometric data of newborns and the characteristics of their biological maturity or age. The latter is significantly more significant for the probability of survival and preservation of the vital functions of the child. The age in weeks of gestation is determined by the sum of scores for 22 clinical signs.

[1], [2], [3], [4]

Signs of the biological maturity of the child

Symptoms	Points
1. Abdominal suspension
The head hangs, the back is arched, the limbs hang straight	0
The head is hanging down, the back is arched, the limbs are almost straight	1
Dorsum slightly arched, limbs slightly bent	2
The head is on the same line with the straight body, the limbs are bent	3
The head is raised, the back is straight, the limbs are bent	4
2. Pulling on the handles
Full head lag	0
Head lag partial	1
Absent	2
Head in front	3
3. Herringbone breast mammary gland
Absent	0
Up to 0.75 cm, smooth and flat, the edges do not rise	2
More than 0.75 cm, the edges are raised	3
4. Transparency of the skin on the abdomen
Numerous veins and venules are visible distinctly	0
The veins and venules are quite distinct	1
Only a few large vessels can be clearly seen	2
You can not see several large vessels vaguely	3
Do not see blood vessels on the belly skin	4
5. Puff on the skin of the back
No gun	0
Abundant, long and thick hair all over the back	1
Thinning of the hair in the lower back	2
There is still a puff, but small areas appear that are devoid of a cannon	3
There is no back in half of the area	4
6. Skin folds
No folds	0
Weak red bands on the anterior part of the plantar side of the foot	1
Clear red stripes, impressions less than 1/3 of the front of the sole	2
Depression of more than 1/3 of the front of the sole	3
Deep, clear folds more than 1/3 of the front of the sole	4
7. Sexual lips
Large open, small protrude outward	0
Large almost completely cover small	1
Large fully cover small	2
8. Eggs
None in the scrotum	0
At least one at the top of the scrotum	1
At least one at the bottom of the scrotum	2
9. Ear shape
The auricle is flat, formless, only parts of its edge are bent inwards	0
The part of the auricle is bent inwards	1
The whole upper part is slightly curved inwards	2
The whole and obviously bent inside	3
10. Hardness of the auricle
The auricle is soft, easily bends and does not return to its original position	0
The auricle is soft, easily bends and slowly returns to its original position	1
The auricle with cartilage on the edge, relatively soft, after bending quickly returns to its original position	2
A firm auricle, immediately returns to its original position	3
11. Mammary glands
Not palpable	0
Less than 0.5 cm in diameter	1
More than 1 cm in diameter	3
12. A square window
66-90 °	0
56-65 °	1
36-55 °	2
11-35 °	3
0-10 °	4
13. Sloping elbow movement
To the axillary line of the opposite side	0
Between the middle line of the body and the axillary line of the opposite side	1
Near the midline of the body	2
Does not reach the middle line	3
14. Response of the foot
180 °	0
90-180 °	1
Less than 90 °	2
15. Hand Response
180 °	0
90-180 °	1
Less than 90 °	2
16. Edema
Explicit edema of hands and feet, pastosity (dimples) above the tibia	0
Only dimples above the tibia	1
Neither edema nor dimple	2
17. The popliteal corner
90 °	5
90-100 °	4
101-120 °	3
121-140 °	2
141-170 °	1
170 °	0
18. Pose
Full bending of hands and feet	4
Legs are bent and divorced, arms slightly bent at the elbows	3
Hands and legs are unbent	0
19. Heel - Ear
Navel	4
Near the nipple	3
Collarbone	2
Chin	1
An ear	0
20. Bending the foot back
0-9 °	4
10-20 °	3
25-50 °	0
55-80 °	1
80-90 °	2
21. Structure of the skin (brushes and feet)
Very thin, gelatinous	0
Thin and smooth	1
Smooth, medium thickness, rash or superficial scaling	2
Thickening, superficial cracks and peeling, especially on hands and feet	3
Pergamentary with superficial and deep cracks	4
22. Skin Color
Dark red	0
Pale pink, relatively uniform	1
Pale pink, uneven	2
Paleness with pink color of ears, lips, palms and soles	3

Score by score

Sum of points	Biological age (weeks)	Sum of points	Biological age (weeks)
0-9	26th	40-43	35
10-12	27th	44-46	36
13-16	28	47-50	37
17-20	29	51-54	38
21-24	Thirty	55-58	39
25-27	31	59-62	40
28-31	32	63-65	41
32-35	33	66-69	42
36-39	34

The norm, or the correspondence of the biological age to the calendar one, to a certain extent testifies to the well-being of the development and functioning of all these systems. The lag of the biological age of the size and proportions of the body can indicate the presence of pathological conditions or inadequate environment for the optimal development of the child.

Anthropometric indicators as a reflection of the biological age of the child

Here, on the one hand, there is full recognition by all researchers of the regular change with age of many ratios of body lengths and widths, and on the other hand, almost complete disregard for the practical use of these regularities for diagnosing the age of biological development of children. The latter is associated with a pronounced variability in the proportions of the body, even in children of the same sex and age. Therefore, a sufficiently accurate diagnosis of biological maturation through body proportions is hardly possible without the development of special methodical techniques. At the same time, even now the body proportions and their age dynamics could be well used in monitoring the individual development of children, especially those with risk factors for deviations from normal growth and maturation. The development of norms for the age proportions of the body in the centile form could be the basis for determining the biological age of the child if there is a sufficiently wide range or set of such standards. If a number of body proportions fall into the 50% zone (from the 25th to the 75th centile) of the same age group, then we can assume that the biological age of the child corresponds to the age of this group.

As proportions that could be normalized for the determination of biological age, the index of the ratio of the head circumference to growth tested in the Research Institute of Hygiene of Children and Adolescents should be listed, as well as a number of indices calculated on the basis of the length ratio: the height of the upper part of the face relative to the length of the body; length of legs relative to body length; the ratio of the upper and lower segments of the body.

The upper part of the face is about 16-18% of the length of the newborn's body, in girls and young men - about 7-8% of the growth.

The length of the newborn's leg is 36-40% of the body length, and by the age of 6-7 it can reach 52-55% of the growth. The ratio of the length of the leg to the height of the upper part of the face has the widest range of age changes and can be calculated without transferring the measurement data as a percentage of the growth of children.

Correlation analysis shows significant statistical relationships between the indexes of body proportions listed and such characteristics of children as the dental formula, the formula for sexual development, physical performance and dynamometry indicators.

To diagnose the completion of the first stretching, a number of authors recommend the so-called Philippine test. To extend the age limits of the use of this test, you can measure it (in centimeters). Finally, in children of the puberty period, the anthropometric indicator of biological maturity can be the index ratio of two transverse diameters - interarchemal (width of shoulders) and intervertebral (pelvic width).

The methodology of using body proportions for estimating biological age in the presence of centile age distributions can be the following.

The first option - if all indices fall into the zone of the 25th-75th centile, one can speak of the child's compliance with this biological age, with some of them left or right - about a tendency to lag behind or outstrip the rate of biological development, shifting all measurements to the left or to the right on centile zones - about a certain lag or ahead of development. At the same time, one can find an age-centile scale where the child's indicators will occupy the position between the 25th and 75th centiles, close to the median, and assume that the child's development (biological age) corresponds most closely to the age for which this coincidence is determined.

The second option - for each measurement or index determine the nearest age median (50th centile) and record the age to which this median belongs, similarly - the second, third index, etc. The biological age of the child can be calculated as the arithmetic mean of the discharged "Ages" of its individual indices or dimensions. The difference between the minimum and maximum age characterizes the severity of heterochrony, or disharmonization, development.

[5], [6], [7],