1 2047 128 EPIGENETIC CLOCKS MAY COME OUT OF RHYTHM-IMPLICATIONS FOR THE ESTIMATION OF CHRONOLOGICAL AGE IN FORENSIC CASEWORK. THERE IS A GROWING PERCEPTION THAT DNA METHYLATION MAY BE INFLUENCED BY EXOGENOUS AND ENDOGENOUS PARAMETERS. KNOWLEDGE OF THESE FACTORS IS OF GREAT RELEVANCE FOR THE INTERPRETATION OF DNA-METHYLATION DATA FOR THE ESTIMATION OF CHRONOLOGICAL AGE IN FORENSIC CASEWORK. WE PERFORMED A LITERATURE REVIEW TO IDENTIFY PARAMETERS, WHICH MIGHT BE OF RELEVANCE FOR THE PREDICTION OF CHRONOLOGICAL AGE BASED ON DNA METHYLATION. THE QUALITY OF AGE PREDICTIONS MIGHT PARTICULARLY BE INFLUENCED BY LIFETIME ADVERSITIES (CHRONIC STRESS, TRAUMA/POST-TRAUMATIC STRESS DISORDER (PTSD), VIOLENCE, LOW SOCIOECONOMIC STATUS/EDUCATION), CANCER, OBESITY AND RELATED DISEASES, INFECTIOUS DISEASES (ESPECIALLY HIV AND CYTOMEGALOVIRUS (CMV) INFECTIONS), SEX, ETHNICITY AND EXPOSURE TO TOXINS (ALCOHOL, SMOKING, AIR POLLUTION, PESTICIDES). SUCH FACTORS MAY ALTER THE DNA METHYLATION PATTERN AND MAY EXPLAIN THE PARTLY HIGH DEVIATIONS BETWEEN EPIGENETIC AGE AND CHRONOLOGICAL AGE IN SINGLE CASES (DESPITE OF LOW MEAN ABSOLUTE DEVIATIONS) THAT CAN ALSO BE OBSERVED WITH "EPIGENETIC CLOCKS" COMPRISING A HIGH NUMBER OF CPG SITES. SO FAR, ONLY FEW PUBLICATIONS DEALING WITH FORENSIC AGE ESTIMATION ADDRESS THESE CONFOUNDING FACTORS. FUTURE RESEARCH SHOULD FOCUS ON THE IDENTIFICATION OF FURTHER RELEVANT CONFOUNDING FACTORS AND THE DEVELOPMENT OF MODELS THAT ARE "ROBUST" AGAINST THE INFLUENCE OF SUCH BIOLOGICAL FACTORS BY SYSTEMATIC INVESTIGATIONS UNDER TARGETED INCLUSION OF DIVERSE AND DEFINED COHORTS. 2020 2 1516 38 DNA METHYLATION AS A BIOMARKER OF AGING IN EPIDEMIOLOGIC STUDIES. CANCER IS LARGELY AN AGING DISEASE. ACCELERATED BIOLOGICAL AGING MAY BE THE STRONGEST PREDICTOR OF CANCER AND OTHER CHRONIC DISEASE RISKS. IN THE ABSENCE OF RELIABLE AND QUANTIFIABLE BIOMARKERS OF AGING TO DATE, IT HAS LONG BEEN OBSERVED THAT TUMORIGENESIS SHARES DISTINCT EPIGENETIC ALTERATIONS WITH THE AGING PROCESS. RECENTLY, EPIGENETIC AGE ESTIMATES HAVE BEEN DEVELOPED BASED ON THE AVAILABILITY OF GENOME-WIDE DNA METHYLATION PROFILES, BY APPLYING IN THE PREDICTION FORMULA THE METHYLATION LEVEL AT A SUBSET OF HIGHLY PREDICTIVE METHYLATION SITES, CALLED EPIGENETIC CLOCK. THESE DNA METHYLATION AGE ESTIMATES HAVE PRODUCED REMARKABLY STRONG CORRELATIONS WITH CHRONOLOGICAL AGE, WITH A SMALL DEVIATION AND HIGH REPRODUCIBILITY ACROSS DIFFERENT AGE GROUPS AND STUDY POPULATIONS. MOREOVER, AN INCREASING NUMBER OF EPIDEMIOLOGIC STUDIES HAVE DEMONSTRATED AN INDEPENDENT ASSOCIATION OF DNA METHYLATION AGE OR THE EXTENT OF ACCELERATION WITH MORTALITY AND VARIOUS AGING-RELATED CONDITIONS, EVEN AFTER ACCOUNTING FOR DIFFERENCES IN CHRONOLOGICAL AGE AND OTHER RISK FACTORS. ALTHOUGH EPIGENETIC PROFILES ARE KNOWN TO BE TISSUE-SPECIFIC, BOTH TARGET TISSUE- AND MULTIPLE TISSUE-DERIVED ESTIMATES APPEAR TO PERFORM WELL TO CAPTURE WHAT IS THOUGHT TO BE THE CUMULATIVE EPIGENETIC DRIFT THAT REPRESENTS A MULTIFACTORIAL DEGENERATIVE PROCESS ACROSS TISSUES AND ORGANISMS. FURTHER REFINEMENT OF THE EPIGENETIC AGE ESTIMATES IS ANTICIPATED OVER TIME TO ACCOMMODATE A BETTER TECHNOLOGICAL COVERAGE OF THE METHYLOME AND A BETTER UNDERSTANDING OF THE BIOLOGY UNDERLYING PREDICTIVE REGIONS. EPIDEMIOLOGIC PRINCIPLES WILL REMAIN CRITICAL FOR THE EVALUATION OF RESEARCH FINDINGS INVOLVING, FOR EXAMPLE, DIFFERENT STUDY POPULATIONS, DESIGN, FOLLOW-UP TIME, AND QUALITY OF COVARIATE DATA. OVERALL, THE EPIGENETIC AGE ESTIMATES ARE AN EXCITING DEVELOPMENT WITH USEFUL IMPLICATIONS FOR BIOMEDICAL RESEARCH OF HEALTHY AGING AND DISEASE PREVENTION AND CONTROL. 2018 3 1206 35 COUNTERACTING AGED DNA METHYLATION STATES TO COMBAT AGEING AND AGE-RELATED DISEASES. DNA METHYLATION (DNAM) OVERWRITES INFORMATION ABOUT MULTIPLE EXTRINSIC FACTORS ON THE GENOME. AGE IS ONE OF THESE FACTORS. AGE CAUSES CHARACTERISTIC DNAM CHANGES THAT ARE THOUGHT TO BE NOT ONLY MAJOR DRIVERS OF NORMAL AGEING BUT ALSO PRECURSORS TO DISEASES, CANCER BEING ONE OF THESE. ALTHOUGH THERE IS STILL MUCH TO LEARN ABOUT THE RELATIONSHIP BETWEEN AGEING, AGE-RELATED DISEASES AND DNAM, WE NOW KNOW HOW TO INTERPRET SOME OF THE EFFECTS CAUSED BY AGE IN THE FORM OF CHANGES IN METHYLATION MARKS AT SPECIFIC LOCI. IN FACT, THESE CHANGES FORM THE BASIS OF THE SO CALLED "EPIGENETIC CLOCKS", WHICH TRANSLATE THE GENOMIC METHYLATION PROFILE INTO AN "EPIGENETIC AGE". EPIGENETIC AGE DOES NOT ONLY ESTIMATE CHRONOLOGICAL AGE BUT CAN ALSO PREDICT THE RISK OF CHRONIC DISEASES AND MORTALITY. EPIGENETIC AGE IS BELIEVED TO BE ONE OF THE MOST ACCURATE METRICS OF BIOLOGICAL AGE. INITIAL EVIDENCE HAS RECENTLY BEEN GATHERED POINTING TO THE POSSIBILITY THAT THE RATE OF EPIGENETIC AGEING CAN BE SLOWED DOWN OR EVEN REVERSED. IN THIS REVIEW, WE DISCUSS SOME OF THE MOST RELEVANT ADVANCES IN THIS FIELD. EXPECTED OUTCOME IS THAT THIS APPROACH CAN PROVIDE INSIGHTS INTO HOW TO PRESERVE HEALTH AND REDUCE THE IMPACT OF AGEING DISEASES IN HUMANS. 2022 4 560 26 BACK TO THE FUTURE: EPIGENETIC CLOCK PLASTICITY TOWARDS HEALTHY AGING. AGING IS THE MOST IMPORTANT RISK FACTOR FOR MAJOR HUMAN LIFESTYLE DISEASES, INCLUDING CANCER, NEUROLOGICAL AND CARDIOMETABOLIC DISORDERS. DUE TO THE COMPLEX INTERPLAY BETWEEN GENETICS, LIFESTYLE AND ENVIRONMENTAL FACTORS, SOME INDIVIDUALS SEEM TO AGE FASTER THAN OTHERS, WHEREAS CENTENARIANS SEEM TO HAVE A SLOWER AGING PROCESS. THEREFORE, A BIOCHEMICAL BIOMARKER REFLECTING THE RELATIVE BIOLOGICAL AGE WOULD BE HELPFUL TO PREDICT AN INDIVIDUAL'S HEALTH STATUS AND AGING DISEASE RISK. ALTHOUGH IT IS ALREADY KNOWN FOR YEARS THAT CUMULATIVE EPIGENETIC CHANGES OCCUR UPON AGING, DNA METHYLATION PATTERNS WERE ONLY RECENTLY USED TO CONSTRUCT AN EPIGENETIC CLOCK PREDICTOR FOR BIOLOGICAL AGE, WHICH IS A MEASURE OF HOW WELL YOUR BODY FUNCTIONS COMPARED TO YOUR CHRONOLOGICAL AGE. MOREOVER, THE EPIGENETIC DNA METHYLATION CLOCK SIGNATURE IS INCREASINGLY APPLIED AS A BIOMARKER TO ESTIMATE AGING DISEASE SUSCEPTIBILITY AND MORTALITY RISK. FINALLY, THE EPIGENETIC CLOCK SIGNATURE COULD BE USED AS A LIFESTYLE MANAGEMENT TOOL TO MONITOR HEALTHY AGING, TO EVALUATE PREVENTIVE INTERVENTIONS AGAINST CHRONIC AGING DISORDERS AND TO EXTEND HEALTHY LIFESPAN. DISSECTING THE MECHANISM OF THE EPIGENETIC AGING CLOCK WILL YIELD VALUABLE INSIGHTS INTO THE AGING PROCESS AND HOW IT CAN BE MANIPULATED TO IMPROVE HEALTH SPAN. 2018 5 625 35 BIOLOGICAL AGE AND ENVIRONMENTAL RISK FACTORS FOR DEMENTIA AND STROKE: MOLECULAR MECHANISMS. SINCE THE DEVELOPMENT OF ANTIBIOTICS AND VACCINATION, AS WELL AS MAJOR IMPROVEMENTS IN PUBLIC HYGIENE, THE MAIN RISK FACTORS FOR MORBIDITY AND MORTALITY ARE AGE AND CHRONIC EXPOSURE TO ENVIRONMENTAL FACTORS, BOTH OF WHICH CAN INTERACT WITH GENETIC PREDISPOSITIONS. AS THE AVERAGE AGE OF THE POPULATION INCREASES, THE PREVALENCE AND COSTS OF CHRONIC DISEASES, ESPECIALLY NEUROLOGICAL CONDITIONS, ARE RAPIDLY INCREASING. THE DELETERIOUS EFFECTS OF AGE AND ENVIRONMENTAL RISK FACTORS, DEVELOP CHRONICALLY OVER RELATIVELY LONG PERIODS OF TIME, IN CONTRAST TO THE RELATIVELY RAPID DELETERIOUS EFFECTS OF INFECTIOUS DISEASES OR ACCIDENTS. OF PARTICULAR INTEREST IS THE HYPOTHESIS THAT THE DELETERIOUS EFFECTS OF ENVIRONMENTAL FACTORS MAY BE MEDIATED BY ACCELERATION OF BIOLOGICAL AGE. THIS HYPOTHESIS IS SUPPORTED BY EVIDENCE THAT DIETARY RESTRICTION, WHICH UNIVERSALLY DELAYS AGE-RELATED DISEASES, ALSO AMELIORATES DELETERIOUS EFFECTS OF ENVIRONMENTAL FACTORS. CONVERSELY, BOTH AGE AND ENVIRONMENTAL RISK FACTORS ARE ASSOCIATED WITH THE ACCUMULATION OF SOMATIC MUTATIONS IN MITOTIC CELLS AND EPIGENETIC MODIFICATIONS THAT ARE A MEASURE OF "BIOLOGICAL AGE", A BETTER PREDICTOR OF AGE-RELATED MORBIDITY AND MORTALITY THAN CHRONOLOGICAL AGE. HERE WE REVIEW EVIDENCE THAT ENVIRONMENTAL RISK FACTORS SUCH AS SMOKING AND AIR POLLUTION MAY ALSO DRIVE NEUROLOGICAL CONDITIONS, INCLUDING ALZHEIMER'S DISEASE, BY THE ACCELERATION OF BIOLOGICAL AGE, MEDIATED BY CUMULATIVE AND PERSISTENT EPIGENETIC EFFECTS AS WELL AS SOMATIC MUTATIONS. ELUCIDATION OF SUCH MECHANISMS COULD PLAUSIBLY ALLOW THE DEVELOPMENT OF INTERVENTIONS WHICH DELAY DELETERIOUS EFFECTS OF BOTH AGING AND ENVIRONMENTAL RISK FACTORS. 2022 6 456 35 APPLYING A LIFE COURSE BIOLOGICAL AGE FRAMEWORK TO IMPROVING THE CARE OF INDIVIDUALS WITH ADULT CANCERS: REVIEW AND RESEARCH RECOMMENDATIONS. IMPORTANCE: THE PRACTICE OF ONCOLOGY WILL INCREASINGLY INVOLVE THE CARE OF A GROWING POPULATION OF INDIVIDUALS WITH MIDLIFE AND LATE-LIFE CANCERS. MANAGING CANCER IN THESE INDIVIDUALS IS COMPLEX, BASED ON DIFFERENCES IN BIOLOGICAL AGE AT DIAGNOSIS. BIOLOGICAL AGE IS A MEASURE OF ACCUMULATED LIFE COURSE DAMAGE TO BIOLOGICAL SYSTEMS, LOSS OF RESERVE, AND VULNERABILITY TO FUNCTIONAL DETERIORATION AND DEATH. BIOLOGICAL AGE IS IMPORTANT BECAUSE IT AFFECTS THE ABILITY TO MANAGE THE RIGORS OF CANCER THERAPY, SURVIVORS' FUNCTION, AND CANCER PROGRESSION. HOWEVER, BIOLOGICAL AGE IS NOT ALWAYS CLINICALLY APPARENT. THIS REVIEW PRESENTS A CONCEPTUAL FRAMEWORK OF LIFE COURSE BIOLOGICAL AGING, SUMMARIZES CANDIDATE MEASURES, AND DESCRIBES A RESEARCH AGENDA TO FACILITATE CLINICAL TRANSLATION TO ONCOLOGY PRACTICE. OBSERVATIONS: MIDLIFE AND LATE-LIFE CANCERS ARE CHRONIC DISEASES THAT MAY ARISE FROM CUMULATIVE PATTERNS OF BIOLOGICAL AGING OCCURRING OVER THE LIFE COURSE. BEFORE DIAGNOSIS, EACH NEW PATIENT WAS ON A DISTINCT COURSE OF BIOLOGICAL AGING RELATED TO PAST EXPOSURES, LIFE EXPERIENCES, GENETICS, AND NONCANCER CHRONIC DISEASE. CANCER AND ITS TREATMENTS MAY ALSO BE ASSOCIATED WITH BIOLOGICAL AGING. SEVERAL MEASURES OF BIOLOGICAL AGE, INCLUDING P16INK4A, EPIGENETIC AGE, TELOMERE LENGTH, AND INFLAMMATORY AND BODY COMPOSITION MARKERS, HAVE BEEN USED IN ONCOLOGY RESEARCH. ONE OR MORE OF THESE MEASURES MAY BE USEFUL IN CANCER CARE, EITHER ALONE OR IN COMBINATION WITH CLINICAL HISTORY AND GERIATRIC ASSESSMENTS. HOWEVER, FURTHER RESEARCH WILL BE NEEDED BEFORE BIOLOGICAL AGE ASSESSMENT CAN BE RECOMMENDED IN ROUTINE PRACTICE, INCLUDING DETERMINATION OF SITUATIONS IN WHICH KNOWLEDGE ABOUT BIOLOGICAL AGE WOULD CHANGE TREATMENT, ASCERTAINING WHETHER TREATMENT EFFECTS ON BIOLOGICAL AGING ARE SHORT-LIVED OR PERSISTENT, AND TESTING INTERVENTIONS TO MODIFY BIOLOGICAL AGE, DECREASE TREATMENT TOXIC EFFECTS, AND MAINTAIN FUNCTIONAL ABILITIES. CONCLUSIONS AND RELEVANCE: UNDERSTANDING DIFFERENCES IN BIOLOGICAL AGING COULD ULTIMATELY ALLOW CLINICIANS TO BETTER PERSONALIZE TREATMENT AND SUPPORTIVE CARE, DEVELOP TAILORED SURVIVORSHIP CARE PLANS, AND PRESCRIBE PREVENTIVE OR AMELIORATIVE THERAPIES AND BEHAVIORS INFORMED BY AGING MECHANISMS. 2021 7 5185 30 PREMATURE PHYSIOLOGIC AGING AS A PARADIGM FOR UNDERSTANDING INCREASED RISK OF ADVERSE HEALTH ACROSS THE LIFESPAN OF SURVIVORS OF CHILDHOOD CANCER. THE IMPROVEMENT IN SURVIVAL OF CHILDHOOD CANCER OBSERVED ACROSS THE PAST 50 YEARS HAS RESULTED IN A GROWING ACKNOWLEDGMENT THAT SIMPLY EXTENDING THE LIFESPAN OF SURVIVORS IS NOT ENOUGH. IT IS INCUMBENT ON BOTH THE CANCER RESEARCH AND THE CLINICAL CARE COMMUNITIES TO ALSO IMPROVE THE HEALTH SPAN OF SURVIVORS. IT IS WELL ESTABLISHED THAT AGING ADULT SURVIVORS OF CHILDHOOD CANCER ARE AT INCREASED RISK OF CHRONIC HEALTH CONDITIONS, RELATIVE TO THE GENERAL POPULATION. HOWEVER, AS THE FIRST GENERATION OF SURVIVORS AGE INTO THEIR 50S AND 60S, IT HAS BECOME INCREASINGLY EVIDENT THAT THIS POPULATION IS ALSO AT RISK OF EARLY ONSET OF PHYSIOLOGIC AGING. GERIATRIC MEASURES HAVE UNCOVERED EVIDENCE OF REDUCED STRENGTH AND SPEED AND INCREASED FATIGUE, ALL COMPONENTS OF FRAILTY, AMONG SURVIVORS WITH A MEDIAN AGE OF 33 YEARS, WHICH IS SIMILAR TO ADULTS OLDER THAN 65 YEARS OF AGE IN THE GENERAL POPULATION. FURTHERMORE, FRAILTY IN SURVIVORS INDEPENDENTLY INCREASED THE RISK OF MORBIDITY AND MORTALITY. ALTHOUGH THERE HAS BEEN A PAUCITY OF RESEARCH INVESTIGATING THE UNDERLYING BIOLOGIC MECHANISMS FOR ADVANCED PHYSIOLOGIC AGE IN SURVIVORS, RESULTS FROM GERIATRIC POPULATIONS SUGGEST FIVE BIOLOGICALLY PLAUSIBLE MECHANISMS THAT MAY BE POTENTIATED BY EXPOSURE TO CANCER THERAPIES: INCREASED CELLULAR SENESCENCE, REDUCED TELOMERE LENGTH, EPIGENETIC MODIFICATIONS, SOMATIC MUTATIONS, AND MITOCHONDRIAL DNA INFIDELITY. THERE IS NOW A CRITICAL NEED FOR RESEARCH TO ELUCIDATE THE BIOLOGIC MECHANISMS OF PREMATURE AGING IN SURVIVORS OF CHILDHOOD CANCER. THIS RESEARCH COULD PAVE THE WAY FOR NEW FRONTIERS IN THE PREVENTION OF THESE LIFE-CHANGING OUTCOMES. 2018 8 247 32 ADULTHOOD ASTHMA AS A CONSEQUENCE OF CHILDHOOD ADVERSITY: A SYSTEMATIC REVIEW OF EPIGENETICALLY AFFECTED GENES. THERE IS AN ACCUMULATING DATA THAT SHOWS RELATION BETWEEN CHILDHOOD ADVERSITY AND VULNERABILITY TO CHRONIC DISEASES AS WELL AS EPIGENETIC INFLUENCES THAT IN TURN GIVE RISE TO THESE DISEASES. ASTHMA IS ONE OF THE CHRONIC DISEASES THAT IS INFLUENCED FROM GENETIC REGULATION OF THE INFLAMMATORY BIOMOLECULES AND THEREFORE THE HYPOTHESIS IN THIS RESEARCH WAS CHILDHOOD ADVERSITY MIGHT HAVE CAUSED EPIGENETIC DIFFERENTIATION IN THE ASTHMA-RELATED GENES IN THE POPULATION WHO HAD CHILDHOOD TRAUMA. TO TEST THIS HYPOTHESIS, THE LITERATURE WAS SYSTEMATICALLY REVIEWED TO EXTRACT EPIGENETICALLY MODIFIED GENE DATA OF THE ADULTS WHO HAD CHILDHOOD ADVERSITY, AND AFFECTED GENES WERE FURTHER EVALUATED FOR THEIR ASSOCIATION WITH ASTHMA. PRISMA GUIDELINES WERE ADOPTED AND PUBMED AND GOOGLE SCHOLAR WERE INCLUDED IN THE SEARCHED DATABASES, TO EVALUATE EPIGENETIC MODIFICATIONS IN ASTHMA-RELATED GENES OF PHYSICALLY, EMOTIONALLY OR SEXUALLY ABUSED CHILDREN. AFTER RETRIEVING A TOTAL OF 5245 ARTICLES, 36 OF THEM WERE INCLUDED IN THE STUDY. SEVERAL GENES AND PATHWAYS THAT MAY CONTRIBUTE TO PATHOGENESIS OF ASTHMA DEVELOPMENT, INCREASED INFLAMMATION, OR RESPONSE TO ASTHMA TREATMENT WERE FOUND EPIGENETICALLY AFFECTED BY CHILDHOOD TRAUMAS. CHILDHOOD ADVERSITY, CAUSING EPIGENETIC CHANGES IN DNA, MAY LEAD TO ASTHMA DEVELOPMENT OR INFLUENCE THE COURSE OF THE DISEASE AND THEREFORE SHOULD BE TAKEN INTO ACCOUNT FOR THE PROLONGED HEALTH CONSEQUENCES. 2022 9 6159 37 THE GENETICS AND EPIGENETICS OF FATIGUE. FATIGUE IS A COMMON SYMPTOM AND INCLUDES BOTH PHYSICAL AND MENTAL COMPONENTS. IT CAN BE ASSOCIATED WITH A VARIETY OF DIFFERENT SYNDROMES AND DISEASES, BUT IN MANY CASES IS NOT ASSOCIATED WITH OTHER COMORBID CONDITIONS. MOST HUMANS HAVE EXPERIENCED ACUTE FATIGUE IN RELATION TO DIFFERENT STRESSORS. ACUTE FATIGUE TYPICALLY DECREASES AS THE EFFECT OF THE TRIGGERING FACTOR IS REDUCED AND A NORMAL HOMEOSTATIC BALANCE IS RESTORED. FATIGUE THAT PERSISTS FOR 6 MONTHS OR MORE IS TERMED CHRONIC FATIGUE. CHRONIC FATIGUE (CF) IN COMBINATION WITH A MINIMUM OF 4 OF 8 SYMPTOMS AND THE ABSENCE OF DISEASES THAT COULD EXPLAIN THESE SYMPTOMS, CONSTITUTE THE CASE DEFINITION FOR CHRONIC FATIGUE SYNDROME. IN SPITE OF ITS PREVALENCE, THE BIOLOGY OF FATIGUE IS RELATIVELY POORLY UNDERSTOOD AND BIOLOGICAL MARKERS HAVE NOT YET BEEN IDENTIFIED. THIS LITERATURE SEARCH WAS PERFORMED IN PUBMED TO IDENTIFY RESEARCH ON THE GENETICS AND EPIGENETICS OF FATIGUE. PUBLICATIONS WERE INCLUDED IF FATIGUE WAS A MAJOR TOPIC AND THE TOPIC WAS COMBINED WITH GENETIC AND/OR EPIGENETIC MEASUREMENTS IN ADULT HUMANS. A TOTAL OF 40 PUBLICATIONS WERE IDENTIFIED. ALTHOUGH ALTERED FUNCTIONING IN THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS, THE SEROTONERGIC SYSTEM, AND ASSOCIATIONS WITH INFECTIOUS AGENTS HAVE BEEN IDENTIFIED, THE SEARCH FOR GENETIC OR EPIGENETIC MARKERS OF FATIGUE, EITHER IN THE CONTEXT OF CF OR CHRONIC FATIGUE SYNDROME (CFS) HAS BEEN RELATIVELY UNPRODUCTIVE OR, IN THE CASE OF EPIGENETICS, NONEXISTENT. ALTHOUGH SEVERAL STUDIES, BOTH HYPOTHESIS-TESTING AND HYPOTHESIS-GENERATING, HAVE BEEN PERFORMED TO SEARCH FOR BIOMARKERS, THEY HAVE MOSTLY BEEN UNDERPOWERED, RESTRICTED BY THE HETEROGENEITY OF THE PHENOTYPE, OR LIMITED BY AN UNSYSTEMATIC STUDY DESIGN. TO BE ABLE TO CONFIRM THE HYPOTHESIS THAT RISK FOR, OR LEVELS OF, FATIGUE ARE INFLUENCED BY THE GENETIC OR EPIGENETIC BACKGROUND OF AN INDIVIDUAL, STUDIES NEED TO BE BASED ON LARGER SAMPLE SIZES WITH A MORE CLEARLY DEFINED PHENOTYPE. STUDIES NEED TO FOCUS NOT ONLY ON THE INFLUENCE OF A SINGLE ASPECT SUCH AS SINGLE NUCLEOTIDE POLYMORPHISMS (SNPS) OR DIFFERENTIAL GENE EXPRESSION ON DISEASE RISK OR STATE, BUT ALSO ON THE SYSTEMS BIOLOGY BEHIND THE DISEASE IN COMBINATION WITH INFORMATION ON ENVIRONMENTAL INFLUENCES AND VALIDATION OF FINDINGS IN FUNCTIONAL STUDIES. 2010 10 739 25 CANCER TREATMENT-INDUCED ACCELERATED AGING IN CANCER SURVIVORS: BIOLOGY AND ASSESSMENT. RAPID IMPROVEMENTS IN CANCER SURVIVAL LED TO THE REALIZATION THAT MANY MODALITIES USED TO TREAT OR CONTROL CANCER MAY CAUSE ACCELERATED AGING IN CANCER SURVIVORS. CLINICALLY, "ACCELERATED AGING" PHENOTYPES IN CANCER SURVIVORS INCLUDE SECONDARY CANCERS, FRAILTY, CHRONIC ORGAN DYSFUNCTION, AND COGNITIVE IMPAIRMENT, ALL OF WHICH CAN IMPACT LONG-TERM HEALTH AND QUALITY OF LIFE IN CANCER SURVIVORS. THE TREATMENT-INDUCED ACCELERATED AGING IN CANCER SURVIVORS COULD BE EXPLAINED BY TELOMERE ATTRITION, CELLULAR SENESCENCE, STEM CELL EXHAUSTION, DNA DAMAGE, AND EPIGENETIC ALTERATIONS. SEVERAL AGING CLOCKS AND BIOMARKERS OF AGING HAVE BEEN PROPOSED TO BE POTENTIALLY USEFUL IN ESTIMATING BIOLOGICAL AGE, WHICH CAN PROVIDE SPECIFIC INFORMATION ABOUT HOW OLD AN INDIVIDUAL IS BIOLOGICALLY INDEPENDENT OF CHRONOLOGICAL AGE. MEASURING BIOLOGICAL AGE IN CANCER SURVIVORS MAY BE IMPORTANT FOR TWO REASONS. FIRST, IT CAN BETTER PREDICT THE RISK OF CANCER TREATMENT-RELATED COMORBIDITIES THAN CHRONOLOGICAL AGE. SECOND, BIOLOGICAL AGE MAY PROVIDE ADDITIONAL VALUE IN EVALUATING THE EFFECTS OF TREATMENTS AND PERSONALIZING CANCER THERAPIES TO MAXIMIZE EFFICACY OF TREATMENT. A DEEPER UNDERSTANDING OF TREATMENT-INDUCED ACCELERATED AGING IN INDIVIDUALS WITH CANCER MAY LEAD TO NOVEL STRATEGIES THAT REDUCE THE ACCELERATED AGING AND IMPROVE THE QUALITY OF LIFE IN CANCER SURVIVORS. 2021 11 5748 35 SOCIAL AND PHYSICAL ENVIRONMENTS EARLY IN DEVELOPMENT PREDICT DNA METHYLATION OF INFLAMMATORY GENES IN YOUNG ADULTHOOD. CHRONIC INFLAMMATION CONTRIBUTES TO A WIDE RANGE OF HUMAN DISEASES, AND ENVIRONMENTS IN INFANCY AND CHILDHOOD ARE IMPORTANT DETERMINANTS OF INFLAMMATORY PHENOTYPES. THE UNDERLYING BIOLOGICAL MECHANISMS CONNECTING EARLY ENVIRONMENTS WITH THE REGULATION OF INFLAMMATION IN ADULTHOOD ARE NOT KNOWN, BUT EPIGENETIC PROCESSES ARE PLAUSIBLE CANDIDATES. WE TESTED THE HYPOTHESIS THAT PATTERNS OF DNA METHYLATION (DNAM) IN INFLAMMATORY GENES IN YOUNG ADULTHOOD WOULD BE PREDICTED BY EARLY LIFE NUTRITIONAL, MICROBIAL, AND PSYCHOSOCIAL EXPOSURES PREVIOUSLY ASSOCIATED WITH LEVELS OF INFLAMMATION. DATA COME FROM A POPULATION-BASED LONGITUDINAL BIRTH COHORT STUDY IN METROPOLITAN CEBU, THE PHILIPPINES, AND DNAM WAS CHARACTERIZED IN WHOLE BLOOD SAMPLES FROM 494 PARTICIPANTS (AGE 20-22 Y). ANALYSES FOCUSED ON PROBES IN 114 TARGET GENES INVOLVED IN THE REGULATION OF INFLAMMATION, AND WE IDENTIFIED 10 SITES ACROSS NINE GENES WHERE THE LEVEL OF DNAM WAS SIGNIFICANTLY PREDICTED BY THE FOLLOWING VARIABLES: HOUSEHOLD SOCIOECONOMIC STATUS IN CHILDHOOD, EXTENDED ABSENCE OF A PARENT IN CHILDHOOD, EXPOSURE TO ANIMAL FECES IN INFANCY, BIRTH IN THE DRY SEASON, OR DURATION OF EXCLUSIVE BREASTFEEDING. TO EVALUATE THE BIOLOGICAL SIGNIFICANCE OF THESE SITES, WE TESTED FOR ASSOCIATIONS WITH A PANEL OF INFLAMMATORY BIOMARKERS MEASURED IN PLASMA OBTAINED AT THE SAME AGE AS DNAM ASSESSMENT. THREE SITES PREDICTED ELEVATED INFLAMMATION, AND ONE SITE PREDICTED LOWER INFLAMMATION, CONSISTENT WITH THE INTERPRETATION THAT LEVELS OF DNAM AT THESE SITES ARE FUNCTIONALLY RELEVANT. THIS PATTERN OF RESULTS POINTS TOWARD DNAM AS A POTENTIALLY IMPORTANT BIOLOGICAL MECHANISM THROUGH WHICH DEVELOPMENTAL ENVIRONMENTS SHAPE INFLAMMATORY PHENOTYPES ACROSS THE LIFE COURSE. 2017 12 120 27 A SYSTEMATIC REVIEW OF CHILDHOOD MALTREATMENT AND DNA METHYLATION: CANDIDATE GENE AND EPIGENOME-WIDE APPROACHES. CHILDHOOD MALTREATMENT IS A MAJOR RISK FACTOR FOR CHRONIC AND SEVERE MENTAL AND PHYSICAL HEALTH PROBLEMS ACROSS THE LIFESPAN. INCREASING EVIDENCE SUPPORTS THE HYPOTHESIS THAT MALTREATMENT IS ASSOCIATED WITH EPIGENETIC CHANGES THAT MAY SUBSEQUENTLY SERVE AS MECHANISMS OF DISEASE. THE CURRENT REVIEW USES A SYSTEMATIC APPROACH TO IDENTIFY AND SUMMARIZE THE LITERATURE RELATED TO CHILDHOOD MALTREATMENT AND ALTERATIONS IN DNA METHYLATION IN HUMANS. A TOTAL OF 100 EMPIRICAL ARTICLES WERE IDENTIFIED IN OUR SYSTEMATIC REVIEW OF RESEARCH PUBLISHED PRIOR TO OR DURING MARCH 2020, INCLUDING STUDIES THAT FOCUSED ON CANDIDATE GENES AND STUDIES THAT LEVERAGED EPIGENOME-WIDE DATA IN BOTH CHILDREN AND ADULTS. THEMES ARISING FROM THE LITERATURE, INCLUDING CONSISTENT AND INCONSISTENT PATTERNS OF RESULTS, ARE PRESENTED. SEVERAL DIRECTIONS FOR FUTURE RESEARCH, INCLUDING IMPORTANT METHODOLOGICAL CONSIDERATIONS FOR FUTURE STUDY DESIGN, ARE DISCUSSED. TAKEN TOGETHER, THE LITERATURE ON CHILDHOOD MALTREATMENT AND DNA METHYLATION UNDERSCORES THE COMPLEXITY OF TRANSACTIONS BETWEEN THE ENVIRONMENT AND BIOLOGY ACROSS DEVELOPMENT. 2021 13 5175 25 PREDICTORS OF BIOLOGICAL AGE: THE IMPLICATIONS FOR WELLNESS AND AGING RESEARCH. AS HEALTHSPAN AND LIFESPAN RESEARCH BREAKTHROUGHS HAVE BECOME MORE COMMONPLACE, THE NEED FOR VALID, PRACTICAL MARKERS OF BIOLOGICAL AGE IS BECOMING INCREASINGLY PARAMOUNT. THE ACCESSIBILITY AND AFFORDABILITY OF BIOLOGICAL AGE PREDICTORS THAT CAN REVEAL INFORMATION ABOUT MORTALITY AND MORBIDITY RISK, AS WELL AS REMAINING YEARS OF LIFE, HAS PROFOUND CLINICAL AND RESEARCH IMPLICATIONS. IN THIS REVIEW, WE EXAMINE 5 GROUPS OF AGING BIOMARKERS CAPABLE OF PROVIDING ACCURATE BIOLOGICAL AGE ESTIMATIONS. THE UNIQUE CAPABILITIES OF THESE BIOMARKERS HAVE FAR REACHING IMPLICATIONS FOR THE TESTING OF BOTH PHARMACEUTICAL AND NON-PHARMACEUTICAL INTERVENTIONS DESIGNED TO SLOW OR REVERSE BIOLOGICAL AGING. ADDITIONALLY, THE ENHANCED VALIDITY AND AVAILABILITY OF THESE TOOLS MAY HAVE INCREASINGLY RELEVANT CLINICAL VALUE. THE AUTHORS OF THIS REVIEW EXPLORE THOSE IMPLICATIONS, WITH AN EMPHASIS ON LIFESTYLE MODIFICATION RESEARCH, AND PROVIDE AN OVERVIEW OF THE CURRENT EVIDENCE REGARDING 5 BIOLOGICAL AGE PREDICTOR CATEGORIES: TELOMERE LENGTH, COMPOSITE BIOMARKERS, DNA METHYLATION "EPIGENETIC CLOCKS," TRANSCRIPTIONAL PREDICTORS OF BIOLOGICAL AGE, AND FUNCTIONAL AGE PREDICTORS. 2021 14 6109 33 THE EPIGENETIC AGING, OBESITY, AND LIFESTYLE. THE PREVALENCE OF OBESITY HAS DRAMATICALLY INCREASED WORLDWIDE OVER THE PAST DECADES. AGING-RELATED CHRONIC CONDITIONS, SUCH AS TYPE 2 DIABETES AND CARDIOVASCULAR DISEASE, ARE MORE PREVALENT IN INDIVIDUALS WITH OBESITY, THUS REDUCING THEIR LIFESPAN. EPIGENETIC CLOCKS, THE NEW METRICS OF BIOLOGICAL AGE BASED ON DNA METHYLATION PATTERNS, COULD BE CONSIDERED A REFLECTION OF THE STATE OF ONE'S HEALTH. SEVERAL ENVIRONMENTAL EXPOSURES AND LIFESTYLE FACTORS CAN INDUCE EPIGENETIC AGING ACCELERATIONS, INCLUDING OBESITY, THUS LEADING TO AN INCREASED RISK OF AGE-RELATED DISEASES. THE INSIGHT INTO THE COMPLEX LINK BETWEEN OBESITY AND AGING MIGHT HAVE SIGNIFICANT IMPLICATIONS FOR THE PROMOTION OF HEALTH AND THE MITIGATION OF FUTURE DISEASE RISK. THE PRESENT NARRATIVE REVIEW TAKES INTO ACCOUNT THE INTERACTION BETWEEN EPIGENETIC AGING AND OBESITY, SUGGESTING THAT EPIGENOME MAY BE AN INTRIGUING TARGET FOR AGE-RELATED PHYSIOLOGICAL CHANGES AND THAT ITS MODIFICATION COULD INFLUENCE AGING AND PROLONG A HEALTHY LIFESPAN. THEREFORE, WE HAVE FOCUSED ON DNA METHYLATION AGE AS A CLINICAL BIOMARKER, AS WELL AS ON THE POTENTIAL REVERSAL OF EPIGENETIC AGE USING A PERSONALIZED DIET- AND LIFESTYLE-BASED INTERVENTION. 2022 15 6065 33 THE DEVELOPMENTAL ORIGINS OF CHRONIC PHYSICAL AGGRESSION: BIOLOGICAL PATHWAYS TRIGGERED BY EARLY LIFE ADVERSITY. LONGITUDINAL EPIDEMIOLOGICAL STUDIES WITH BIRTH COHORTS HAVE SHOWN THAT PHYSICAL AGGRESSION IN HUMANS DOES NOT APPEAR SUDDENLY IN ADOLESCENCE AS COMMONLY THOUGHT. IN FACT, PHYSICALLY AGGRESSIVE BEHAVIOUR IS OBSERVED AS EARLY AS 12 MONTHS AFTER BIRTH, ITS FREQUENCY PEAKS AROUND 2-4 YEARS OF AGE AND DECREASES IN FREQUENCY UNTIL EARLY ADULTHOOD. HOWEVER, A MINORITY OF CHILDREN (3-7%) MAINTAIN A HIGH FREQUENCY OF PHYSICAL AGGRESSION FROM CHILDHOOD TO ADOLESCENCE AND DEVELOP SERIOUS SOCIAL ADJUSTMENT PROBLEMS DURING ADULTHOOD. GENETIC FACTORS AND EARLY SOCIAL EXPERIENCES, AS WELL AS THEIR INTERACTION, HAVE BEEN SHOWN TO PLAY AN IMPORTANT ROLE IN THE DEVELOPMENT OF CHRONIC AGGRESSIVE BEHAVIOUR. HOWEVER, THE BIOLOGICAL MECHANISMS UNDERLYING THESE ASSOCIATIONS ARE JUST BEGINNING TO BE UNCOVERED. RECENT EVIDENCE SUGGESTS THAT EPIGENETIC MECHANISMS ARE RESPONSIVE TO ADVERSE ENVIRONMENTS AND COULD BE INVOLVED IN THE DEVELOPMENT OF CHRONIC AGGRESSION. USING BOTH GENE CANDIDATE AND GENOMIC APPROACHES, RECENT STUDIES HAVE IDENTIFIED EPIGENETIC MARKS, SUCH AS DNA METHYLATION ALTERATIONS IN GENES INVOLVED IN THE STRESS RESPONSE AND THE SEROTONIN AND IMMUNE SYSTEMS TO BE PARTLY RESPONSIBLE FOR THE LONG-LASTING EFFECTS OF EARLY ADVERSITY. FURTHER LONGITUDINAL STUDIES WITH BIOLOGICAL, ENVIRONMENTAL AND BEHAVIOURAL ASSESSMENTS FROM BIRTH ONWARDS ARE NEEDED TO ELUCIDATE THE SEQUENCE OF EVENTS THAT LEADS TO THESE LONG-LASTING EPIGENETIC MARKS ASSOCIATED WITH EARLY ADVERSITY AND AGGRESSION. 2015 16 2677 27 EVALUATING THE CHALLENGES AND REPRODUCIBILITY OF STUDIES INVESTIGATING DNA METHYLATION SIGNATURES OF PSYCHOLOGICAL STRESS. PSYCHOLOGICAL STRESS CAN INCREASE THE RISK OF A WIDE RANGE OF NEGATIVE HEALTH OUTCOMES. STUDIES HAVE BEEN COMPLETED TO DETERMINE IF DNA METHYLATION CHANGES OCCUR IN THE HUMAN BRAIN BECAUSE OF STRESS AND ARE ASSOCIATED WITH LONG-TERM EFFECTS AND DISEASE, BUT RESULTS HAVE BEEN INCONSISTENT. HUMAN CANDIDATE GENE STUDIES (150) AND EPIGENOME-WIDE ASSOCIATION STUDIES (67) WERE SYSTEMATICALLY EVALUATED TO ASSESS HOW DNA METHYLATION IS IMPACTED BY STRESS DURING THE PRENATAL PERIOD, EARLY CHILDHOOD AND ADULTHOOD. THE ASSOCIATION BETWEEN DNA METHYLATION OF NR3C1 EXON 1F AND CHILD MALTREATMENT AND EARLY LIFE ADVERSITY WAS WELL DEMONSTRATED, BUT OTHER GENES DID NOT EXHIBIT A CLEAR ASSOCIATION. THE REPRODUCIBILITY OF INDIVIDUAL CPG SITES IN EPIGENOME-WIDE ASSOCIATION STUDIES WAS ALSO POOR. HOWEVER, BIOLOGICAL PATHWAYS, INCLUDING STRESS RESPONSE, BRAIN DEVELOPMENT AND IMMUNITY, HAVE BEEN CONSISTENTLY IDENTIFIED ACROSS DIFFERENT STRESSORS THROUGHOUT THE LIFE SPAN. FUTURE STUDIES WOULD BENEFIT FROM THE INCREASED SAMPLE SIZE, LONGITUDINAL DESIGN, STANDARDIZED METHODOLOGY, OPTIMAL QUALITY CONTROL, AND IMPROVED STATISTICAL PROCEDURES. 2022 17 1045 29 CLINICAL CORRELATION AMONG MALE INFERTILITY AND OVERALL MALE HEALTH: A SYSTEMATIC REVIEW OF THE LITERATURE. PURPOSE: ONGOING EVIDENCE HAS SUGGESTED THE ROLE OF MALE FACTOR INFERTILITY AS A POTENTIAL PREDICTOR OF MORTALITY AND GENERAL HEALTH STATUS. THE AIM OF THE PRESENT REVIEW IS TO UPDATE THE CURRENT KNOWLEDGE BASE REGARDING THE ASSOCIATION BETWEEN MALE FACTOR INFERTILITY AND GENERAL HEALTH THROUGH A CRITICAL REVIEW OF THE LITERATURE. MATERIALS AND METHODS: A SYSTEMATIC REVIEW OF THE LITERATURE WAS CARRIED OUT FROM INCEPTION TO NOVEMBER 2019 IN ORDER TO EVALUATE SIGNIFICANT ASSOCIATIONS BETWEEN MALE INFERTILITY AND ADVERSE HEALTH OUTCOMES SUCH AS CARDIOVASCULAR, ONCOLOGIC, METABOLIC AND AUTOIMMUNE DISEASES AS WELL AS OVERALL MORTALITY. RESULTS: IN ALL, 27 STUDIES MET INCLUSION CRITERIA AND WERE CRITICALLY EXAMINED. FIVE STUDIES EXAMINED MALE INFERTILITY AND CARDIOVASCULAR DISEASE RISK, 11 EXAMINED ONCOLOGIC RISK (E.G., OVERALL CANCER RISK, TESTIS AND PROSTATE CANCER), 8 EXAMINED AGGREGATE CHRONIC MEDICAL DISEASES AND 5 INFERTILITY RELATED TO INCIDENCE OF MORTALITY, FOR A TOTAL OF 599,807 MEN DIAGNOSED WITH ANY MALE FACTOR INFERTILITY COVERING A PERIOD FROM 1916 TO 2016. CONCLUSIONS: A MAN'S FERTILITY AND OVERALL HEALTH APPEAR TO BE INTERCONNECTED. THEREFORE, A DIAGNOSIS OF MALE INFERTILITY MAY ALLOW A WINDOW INTO FUTURE COMORBIDITY AND/OR MORTALITY WHICH MAY HELP GUIDE CLINICAL DECISIONS AND COUNSELING. SEVERAL POSSIBLE ETIOLOGIES SUCH AS GENETIC, EPIGENETIC, DEVELOPMENTAL, AND LIFESTYLE-BASED FACTORS NEED TO BE FURTHER EVALUATED IN ORDER TO ESTABLISH THE UNDERLYING MECHANISMS BETWEEN MALE INFERTILITY AND HEALTH. 2020 18 2651 35 EPIGENOMICS AND TRANSCRIPTOMICS IN THE PREDICTION AND DIAGNOSIS OF CHILDHOOD ASTHMA: ARE WE THERE YET? ASTHMA IS THE MOST COMMON NON-COMMUNICABLE CHRONIC DISEASE OF CHILDHOOD. DESPITE ITS HIGH PREVALENCE, TO DATE WE LACK METHODS THAT ARE BOTH EFFICIENT AND ACCURATE IN DIAGNOSING ASTHMA. MOST TRADITIONAL APPROACHES HAVE BEEN BASED ON GARNERING CLINICAL EVIDENCE, SUCH AS RISK FACTORS AND EXPOSURES. GIVEN THE HIGH HERITABILITY OF ASTHMA, MORE RECENT APPROACHES HAVE LOOKED AT GENETIC POLYMORPHISMS AS POTENTIAL "RISK FACTORS." HOWEVER, GENETIC VARIANTS EXPLAIN ONLY A SMALL PROPORTION OF ASTHMA RISK, AND HAVE BEEN LESS THAN OPTIMAL AT PREDICTING RISK FOR INDIVIDUAL SUBJECTS. EPIGENOMIC STUDIES OFFER SIGNIFICANT ADVANTAGES OVER PREVIOUS APPROACHES. EPIGENETIC REGULATION IS HIGHLY TISSUE-SPECIFIC, AND CAN INDUCE BOTH SHORT- AND LONG-TERM CHANGES IN GENE EXPRESSION. SUCH CHANGES CAN START IN UTERO, CAN VARY THROUGHOUT THE LIFE SPAN, AND IN SOME INSTANCES CAN BE PASSED ON FROM ONE GENERATION TO ANOTHER. MOST IMPORTANTLY, THE EPIGENOME CAN BE MODIFIED BY ENVIRONMENTAL FACTORS AND EXPOSURES, AND THUS EPIGENETIC AND TRANSCRIPTOMIC PROFILING MAY YIELD THE MOST ACCURATE RISK ESTIMATES FOR A GIVEN PATIENT BY INCORPORATING ENVIRONMENTAL (AND TREATMENT) EFFECTS THROUGHOUT THE LIFESPAN. HERE WE WILL REVIEW THE MOST RECENT ADVANCES IN THE USE OF EPIGENETIC AND TRANSCRIPTOMIC ANALYSIS FOR THE EARLY DIAGNOSIS OF ASTHMA AND ATOPY, AS WELL AS CHALLENGES AND FUTURE DIRECTIONS IN THE FIELD AS IT MOVES FORWARD. WE WILL PARTICULARLY FOCUS ON DNA METHYLATION, THE MOST STUDIED MECHANISM OF EPIGENETIC REGULATION. 2019 19 1324 30 DEOXYRIBONUCLEIC ACID (DNA) METHYLATION IN CHILDREN EXPOSED TO AIR POLLUTION: A POSSIBLE MECHANISM UNDERLYING RESPIRATORY HEALTH EFFECTS DEVELOPMENT. AIR POLLUTION IS A SUBSTANTIAL ENVIRONMENTAL THREAT TO CHILDREN AND ACTS AS ACUTE AND CHRONIC DISEASE RISK FACTORS ALIKE. SEVERAL STUDIES HAVE PREVIOUSLY EVALUATED EPIGENETIC MODIFICATIONS CONCERNING ITS EXPOSURE ACROSS VARIOUS LIFE STAGES. HOWEVER, FINDINGS ON EPIGENETIC MODIFICATIONS AS THE CONSEQUENCES OF AIR POLLUTION DURING CHILDHOOD ARE RATHER MINIMAL. THIS REVIEW EVALUATED HIGHLY RELEVANT STUDIES IN THE FIELD TO ANALYZE THE EXISTING LITERATURE REGARDING EXPOSURE TO AIR POLLUTION, WITH A FOCUS ON EPIGENETIC ALTERATIONS DURING CHILDHOOD AND THEIR CONNECTIONS WITH RESPIRATORY HEALTH EFFECTS. THE SEARCH WAS CONDUCTED USING READILY AVAILABLE ELECTRONIC DATABASES (PUBMED AND SCIENCEDIRECT) TO SCREEN FOR CHILDREN'S STUDIES ON EPIGENETIC MECHANISMS FOLLOWING EITHER PRE- OR POST-NATAL EXPOSURE TO AIR POLLUTANTS. STUDIES RELEVANT ENOUGH AND MATCHED THE PREDETERMINED CRITERIA WERE CHOSEN TO BE REVIEWED. NON-ENGLISH ARTICLES AND STUDIES THAT DID NOT REPORT BOTH AIR MONITORING AND EPIGENETIC OUTCOMES IN THE SAME ARTICLE WERE EXCLUDED. THE REVIEW FOUND THAT EPIGENETIC CHANGES HAVE BEEN LINKED WITH EXPOSURE TO AIR POLLUTANTS DURING EARLY LIFE WITH EVIDENCE AND REPORTS OF HOW THEY MAY DEREGULATE THE EPIGENOME BALANCE, THUS INDUCING DISEASE PROGRESSION IN THE FUTURE. EPIGENETIC STUDIES EVOLVE AS A PROMISING NEW APPROACH IN DECIPHERING THE UNDERLYING IMPACTS OF AIR POLLUTION ON DEOXYRIBONUCLEIC ACID (DNA) DUE TO LINKS ESTABLISHED BETWEEN SOME OF THESE EPIGENETIC MECHANISMS AND ILLNESSES. 2021 20 2901 34 GENDER DIFFERENCES IN GERM-CELL MUTAGENESIS AND GENETIC RISK. CURRENT INTERNATIONAL CLASSIFICATION SYSTEMS FOR CHEMICAL MUTAGENS ARE HAZARD-BASED RATHER THAN AIMED AT ASSESSING RISKS QUANTITATIVELY. IN THE PAST, GERM-CELL TESTS HAVE BEEN MAINLY PERFORMED WITH A LIMITED NUMBER OF SOMATIC CELL MUTAGENS, AND RARELY UNDER CONDITIONS AIMED AT COMPARING GENDER-SPECIFIC DIFFERENCES IN SUSCEPTIBILITY TO MUTAGEN EXPOSURES. THERE ARE PROFOUND DIFFERENCES IN THE GENETIC CONSTITUTION, AND IN HORMONAL, STRUCTURAL, AND FUNCTIONAL ASPECTS OF DIFFERENTIATION AND CONTROL OF GAMETOGENESIS BETWEEN THE SEXES. A CRITICAL REVIEW OF THE LITERATURE SUGGESTS THAT THESE DIFFERENCES MAY HAVE A PROFOUND IMPACT ON THE RELATIVE SUSCEPTIBILITY, STAGE OF HIGHEST SENSITIVITY AND THE RELATIVE RISK FOR THE GENESIS OF GENE MUTATION, AS WELL AS STRUCTURAL AND NUMERICAL CHROMOSOMAL ABERRATIONS IN MALE AND FEMALE GERM CELLS. TRANSMISSION OF GERM-CELL MUTATIONS TO THE OFFSPRING MAY ALSO ENCOUNTER GENDER-SPECIFIC INFLUENCES. GENDER DIFFERENCES IN SUSCEPTIBILITY TO CHEMICALLY DERIVED ALTERATIONS IN IMPRINTING PATTERNS MAY POSE A THREAT FOR THE HEALTH OF THE OFFSPRING AND MAY ALSO BE TRANSMITTED TO FUTURE GENERATIONS. RECENT REPORTS ON DIFFERENT GENETIC EFFECTS FROM HIGH ACUTE AND FROM CHRONIC LOW-DOSE EXPOSURES CHALLENGE THE VALIDITY OF CONCLUSIONS DRAWN FROM STANDARD METHODS OF MUTAGENICITY TESTING. IN CONCLUSION, RESEARCH IS URGENTLY NEEDED TO IDENTIFY GENETIC HAZARDS FOR A LARGER RANGE OF CHEMICAL COMPOUNDS, INCLUDING THOSE SUSPECTED TO DISTURB PROPER CHROMOSOME SEGREGATION. ALTERATIONS IN EPIGENETIC PROGRAMMING AND THEIR HEALTH CONSEQUENCES WILL HAVE TO BE INVESTIGATED. MORE ATTENTION SHOULD BE PAID TO GENDER-SPECIFIC GENETIC EFFECTS. FINALLY, THE DATABASE FOR GERM-CELL MUTAGENS SHOULD BE ENLARGED USING MOLECULAR METHODOLOGIES, AND GENETIC EPIDEMIOLOGY STUDIES SHOULD BE PERFORMED WITH THESE TECHNIQUES TO VERIFY HUMAN GENETIC RISK. 2007