Future healthy longevity starts at conception

 Highlights:

• Childhood habits such as dietary choices, physical activity, and emotional self-control significantly impact lifespan and healthspan.
• Childhood adversity, such as socioeconomic deprivation, is associated with greater mortality risk in later life and reduced lifespan, influencing the hallmarks of aging, such as telomere attrition and epigenetic alterations.
• The brain is vulnerable and adaptable as the primary organ of stress and adaptation, and it changes structurally and functionally due to prolonged childhood acute stress.
• Early-life experiences affect adult health in at least two ways: accumulating damage over time and biological embedding of adversities during sensitive developmental periods.

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Introduction

Adult conditions, such as cardiovascular diseases (CVD), diabetes, and cancer, were seen as products of only adult behavior and lifestyles for most of the 20th century. But now, we have a growing body of evidence linking adult chronic diseases to childhood experiences. 

Longitudinal studies have shown that pulmonary disease in adulthood is often associated with a history of childhood respiratory illnesses. Prenatal processes are associated with the later development of schizophrenia and autism, and CVD in later life is linked to nutritional deficits and growth impairments in the fetal period. Also, socioeconomic environments are intensely involved in cognitive and socioemotional development starting at an early age. Therefore, longevity begins in childhood.

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Habit building starts at conception

Early childhood is essential for establishing behaviors that will affect general health throughout life. For example, breastfeeding, child physical activity, and electronic media exposure among infants and young children are likely determinants of childhood obesity. 

Parents play a primary role in shaping these behaviors through parental modeling, feeding styles, and the food and physical activity environments provided. Children coming from low socioeconomic backgrounds have higher rates of obesity, making early intervention particularly important (1).

• Diet

According to the Centers for Disease Control and Prevention (CDC), the prevalence of obesity among children and teenagers is very high. For those aged 2–19 years in 2017–2020, it was 19.7% and affected about 14.7 million American children and teenagers. 

Obesity is related to high blood pressure, high cholesterol levels, type 2 diabetes, breathing issues, and joint problems. And the earlier it starts, the more significant the toll on longevity (2). There is increasing evidence that the same risk profile partially determines cardiometabolic risk in adulthood and in childhood, and early-age diet is one of the strongest determinants of cardiovascular disease risk factors (3, 4). Additionally, childhood diets show some degree of tracking into adulthood and are associated with adulthood cardiovascular risk factors (4).

• Physical activity

When it comes to a habit of healthy physical activity, the CDC states that less than one-quarter (24%) of children aged 6 to 17 participated in the suggested 60 minutes of physical activity every day. Physical inactivity can lead to energy imbalance and a higher risk of becoming overweight or obese. It elevates the risk factors for cardiovascular diseases, including hyperlipidemia, high blood pressure, insulin resistance, and glucose intolerance. Physical inactivity increases the risk of developing type 2 diabetes and cancer, and leading to low bone density and later osteoporosis (5, 6). It also worsens brain and metabolic health and can cause depression in adults (7, 8).

• Sleep

According to the CDC, middle and high schoolers do not get the recommended amount of sleep per day. In the U.S., based on parent reports, 34.9% of individuals between the age of 4 months and 17 years slept less than recommended. Insufficient sleep is connected with a higher risk of type -2 diabetes, obesity, poor mental health, injuries, and attention and behavioral problems (9).

• Electronic media use

Electronic media use is measured by screen time, defined as the time spent in front of the television, computers, phones, and others. The American Academy of Pediatrics recommends less than 2 hours of screen time a day for preschoolers and does not recommend electronic media use for children under the age of two. A study at the University of Washington found that 66% of children exceed this limit. Screen time is linked to increased obesity among children and adolescents and reduced time spent on exercise (10).

• Emotional health

Another interesting habit is the ability to control one's emotions, thoughts, and behaviors early in life.  Children with better self-control aged slower in adulthood, and their brains showed fewer signs of aging in adulthood. By midlife, these children were better equipped to manage various later-life health, financial, and social demands (11).

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As the twig is bent, so is the tree inclined

Childhood behavioral habits are only the tip of the iceberg. As early as the fetal stage, the human body senses the surrounding environment, which trains the adaptation strategies to an external world. Unfortunately, when early experiences prepare a developing child for conditions involving a high level of stress or instability, the body's systems retain the initial programming and put the stress response system on a short-fuse and high-alert status. Under such circumstances, short-term survival benefits may come at a high cost to long-term health (12).

Childhood adversity, such as socioeconomic deprivation, is associated with greater mortality risk in later life and reduced lifespan (12). Intense, frequent, and prolonged adversity experiences during childhood without adequate adult support lead to a toxic stress response (13). In the psychosocial domain, early-age toxic stressors, such as abuse, parental mental illness, and household criminality, are related to higher risks of adult diseases and health-compromising behaviors. 

Childhood socioeconomic disadvantage is associated with individual cardiovascular risk factor levels in adulthood. In addition, childhood socioeconomic circumstances and intergenerational education mobility are associated with health-related behaviors in adulthood (3). Early supportive relationships are vital determinants of developmental outcomes (14). Parenting style has a tremendous impact on late-life mortality and healthspan. For example, a parenting style characterized by low care levels and high levels of overprotection was linked to greater mortality risk (15). Also, in childhood, passive smoking due to smoking parents is associated with worse cardiovascular health in adulthood (3).

According to research, early toxic stress can affect adult health in at least two ways:

1. Accumulating damage over time – repetitive traumatic childhood events lead to a higher prevalence of conditions such as coronary artery disease, chronic pulmonary disease, cancer, alcoholism, depression, or drug abuse. Increased wear and tear induced by stressful experiences, overuse, and dysregulated pathways typically used for adaptation to threat. These pathways include the secretion of stress hormones, increased heart rate and blood pressure, protective mobilization of nutrients, redirection of blood perfusion to the brain, and induction of vigilance and fear. These neurobiological responses are essential and generally protective, but they can become pathogenic when activated persistently under chronic or overwhelming adversity circumstances.
2. Biological embedding of adversities during sensitive developmental periods – Adult disease and risk factors for poor health can be embedded biologically during sensitive periods, in which the developing brain is more receptive to environmental signals. For example, poor living conditions early in life (inadequate nutrition, other constraints on fetal and infant growth, and recurrent infections) are associated with increased cardiovascular, respiratory, and psychiatric diseases in adulthood. Also, early experiences of child maltreatment and poverty have been associated with heightened immune responses in adulthood, which are known risk factors for developing  CVD, diabetes, asthma, and chronic lung disease.

In both cases, there can be a delay of many years, or even decades, before early adverse experiences are expressed as a disease.

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The central role of the brain

The brain is vulnerable and malleable as the primary organ of stress and adaptation. It interprets and regulates behavioral, neuroendocrine, immunological, and other responses to stressful events. It is a target of acute and chronic psychosocial and physical stress and changes structurally and functionally due to significant adversity. 

Stress-induced remodeling of neuronal structure and connectivity alters behavioral and physiological responses, including anxiety, aggression, mental flexibility, memory, and other cognitive processes. Children from lower socioeconomic backgrounds show increased activation of stress-responsive systems. 

Differences in parenting related to income and education, e.g., the quality of parent-child interaction or exposure to new vocabulary, can alter the maturation of selected brain areas, such as the prefrontal cortex (12). On the other hand, the active brain in childhood stays in better shape longer. Frequent cognitive activity in early life is associated with slower cognitive decline (16).

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Childhood experiences vs. the hallmarks of aging

Epigenetic alterations obtained in utero and early life might have a life-long lasting impact on gene expression and phenotypes. These alterations, which are a hallmark of aging, affect gene expression by influencing DNA methylation, chromatin remodeling, and microRNA-regulated transcriptional silencing without changes in the DNA sequence.

Prenatal stress and early postnatal influences have well-established long-term consequences, and there are some indications that the impact of early environmental stress is observable until senescence. Most childhood stress-induced modifications are reversed to the normal level once the stress is relieved, but some modifications may be stable, leading to accelerated aging (17).

In 2016, Puterman et al. examined the relationship between cumulative childhood and adulthood adversity and salivary telomere length. Telomere attrition is another hallmark of aging. 

The research has proven that single misfortunes tended to have nonsignificant relations with telomere length, while lifetime cumulative adversity predicted 6% greater odds of shorter telomeres. In adjusted models for cumulative childhood adversity, the occurrence of each additional childhood event predicted an 11% increase in the odds of having short telomeres. This study suggests that the shadow of childhood adversity may reach far into later adulthood, partly through cellular aging (18). Luckily, not all children experiencing adversity are at similar risk due to resiliency (12, 18, 19).

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Not all childhood stress is bad: hormesis

Hormesis is a phenomenon in which otherwise harmful factors benefit living organisms when they are exposed to them in small quantities. Hormetic and lifespan-extending interventions might be more efficient if they are applied in childhood. In particular, microbial exposures in early childhood can protect against subsequent allergies and even cancer. For example, children who attend daycare in their first few months are much less likely to develop leukemia than those who stay home (20). 

Another kind of mild hormetic stress is repeated temperature change. Sharp temperature alteration, such as ice-hole swimming after the sauna, is an important component of the traditional healthy Russian lifestyle. It is necessary to begin such training under the physician's control, and the highest effect could be expected when it starts in early childhood. Because the heat shock protein response is a common feature of various stresses, adaptation to extreme temperatures could be translated into adaptation to other stresses as well (17).

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It starts with parental guidance

The parents mold the child. Pediatricians, health coaches, or nutritionists should mention to the parents that:

• The child copies the habits of their parents.
• Childhood habits such as diet, amount of physical exercise, and sleep could have long-lasting effects on the child's future health.
• Childhood habits should be monitored and influenced by parents.
• The environment in which the child grows tremendously impacts their development, health, and longevity.
• Passive smoking harms the child, and smoking at home should be avoided.
• Childhood adversity, such as socioeconomic deprivation, is associated with greater mortality risk in later life and reduced lifespan.
• Early-age severe stressors such as abuse, parental mental illness, and household criminality are related to higher risks of adult diseases and health-compromising behaviors.
• Parenting style has a tremendous impact on late-life mortality and healthspan.
• Parenting style, characterized by low levels of care and high levels of overprotection, is associated with greater mortality risk.
• Childhood toxic stress remodels the neuronal structure and alters behavioral and physiological responses, including anxiety, aggression, mental flexibility, and memory.
• Hormetic stress, such as early-childhood microbial exposures, can protect against subsequent allergies and cancer.

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Conclusions

Investments in health during childhood play a crucial role in later life and improve an individual's educational attainment, income, and other life prospects. All these returns may extend beyond childhood and throughout life (21). Care for physical and mental health early in life could have better effects than improved access to health care and health-related behaviors tweaking in adulthood (12). And as longevity starts in childhood, parents should be aware of their parenting impact on the future health of their offspring.

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References

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