Hair Loss Among Elderly Men: Etiology and Impact on Perceived Age

Analysis of 72,469 UK Biobank exomes links rare variants to male-pattern hair loss

Male-pattern hair loss (MPHL) is common and highly heritable. While genome-wide association studies (GWAS) have generated insights into the contribution of common variants to MPHL etiology, the relevance of rare variants remains unclear. To determine the contribution of rare variants to MPHL etiology, we perform gene-based and single-variant analyses in exome-sequencing data from 72,469 male UK Biobank participants. While our population-level risk prediction suggests that rare variants make only a minor contribution to general MPHL risk, our rare variant collapsing tests identified a total of five significant gene associations. These findings provide additional evidence for previously implicated genes (EDA2R, WNT10A) and highlight novel risk genes at and beyond GWAS loci (HEPH, CEPT1, EIF3F). Furthermore, MPHL-associated genes are enriched for genes considered causal for monogenic trichoses. Together, our findings broaden the MPHL-associated allelic spectrum and provide insights into MPHL pathobiology and a shared basis with monogenic hair loss disorders.

Male-pattern hair loss: Comprehensive identification of the associated genes as a basis for understanding pathophysiology

Male-pattern hair loss (MPHL) is a highly heritable and prevalent condition that is characterized by progressive hair loss from the frontotemporal and vertex scalp. This androgen-dependent hair loss may commence during puberty, and up to 80 % of European men experience some degree of MPHL during their lifetime. Current treatment options for MPHL have limited efficacy, and improved understanding of the underlying biological causes is required to facilitate novel therapeutic approaches. To date, molecular genetic studies have identified 389 associated genomic regions, have implicated numerous genes in these regions, and suggested pathways that are likely to contribute to key pathophysiological mechanisms in MPHL. This review provides an overview of the current status of MPHL genetic research. We discuss the most significant achievements, current challenges, and anticipated developments in the field, as well as their potential to advance our understanding of hair (loss) biology, and to improve hair loss prediction and treatment.

Hair disorder in cosmetic dermatology venereology outpatient clinic of dr. Cipto Mangunkusumo Jakarta: socio-demographic and clinical evaluation

Hair disorder has a significant impact on sociopsychology. In Indonesia, there are currently few and out-of-date studies on hair disorders. Our study aimed to provide an update on the epidemiology of hair loss, which is common in Indonesia. This is a retrospective study of hair disorder cases seen at Dr. Cipto Mangunkusumo’s Cosmetic Dermatology Outpatient Clinic at the National Central General Hospital from January 2017 to December 2019. Each patient’s age, gender, family history, education, occupation, body mass index (BMI), comorbidities, and diagnosis were recorded. Hair disorders were found to be more prevalent in males (54.6 percent) with a mean age of 26.41 ± 12.8 years old and the highest age group of 18-39 years old (59.4 percent) among the 64 patients who were eligible for the study. There were 32 cases (50.0%) of alopecia areata (AA), 20 cases (31.2%) of alopecia androgenetic (AGA), 9 cases (14.0%) of telogen effluvium (TE), 2 cases of cicatricial alopecia (CA) due to lupus erythematosus (DLE), and 1 case of trichotillomania (TTM). Female patients had significantly more TE cases. Cases of AGA in the study, mainly early-onset AGA (mean age 29.45 ± 10.29 years old, 39.5% in 18-39 years old) showed a significant positive familial history. At dr Cipto Mangunkusumo National General Hospital Jakarta, the most common types of hair disorders were AA, AGA, and TE, with each disease having a unique socio-demographic and clinical profile.

Observations that suggest a contribution of altered dermal papilla mitochondrial function to androgenetic alopecia

Androgenetic alopecia (AGA) is a prevalent hair loss condition in males that develops due to the influence of androgens and genetic predisposition. With the aim of elucidating genes involved in AGA pathogenesis, we modelled AGA with three-dimensional culture of keratinocyte-surrounded dermal papilla (DP) cells. We co-cultured immortalised balding and non-balding human DP cells (DPC) derived from male AGA patients with epidermal keratinocyte (NHEK) using multi-interfacial polyelectrolyte complexation technique. We observed up-regulated mitochondria-related gene expression in balding compared to non-balding DP aggregates which indicated altered mitochondria metabolism. Further observation of significantly reduced electron transport chain complex activity (complex I, IV and V), ATP levels and ability to uptake metabolites for ATP generation demonstrated compromised mitochondria function in balding DPC. Balding DP was also found to be under significantly higher oxidative stress than non-balding DP. Our experiments suggest that application of antioxidants lowers oxidative stress levels and improve metabolite uptake in balding DPC. We postulate that the observed up-regulation of mitochondria-related genes in balding DP aggregates resulted from an over-compensatory effort to rescue decreased mitochondrial function in balding DP through the attempted production of new functional mitochondria. In all, our three-dimensional co-culturing revealed mitochondrial dysfunction in balding DPC, suggesting a metabolic component in the etiology of AGA.

Scalp Microbiome and Sebum Composition in Japanese Male Individuals with and without Androgenetic Alopecia

The skin microbiome and sebum may be associated with inflammation-related diseases of the scalp. To assess the pathogenesis and progression of androgenetic alopecia (AGA), we analyzed the composition of sebum and the bacterial and fungal microbiomes of the scalps of 118 Japanese male individuals with and without AGA, then discussed their roles in the pathogenesis of AGA. Sebum triglyceride and palmitic acid contents were higher in the AGA group than in the non-AGA group. Malassezia restricta, a lipophilic fungus that consumes palmitic acid, was abundant on the scalps of patients with AGA. Cutibacterium, Corynebacterium, and Staphylococcus were the most common genera in both groups, and patients with AGA exhibited scalp dysbiosis (increased abundance of Cutibacterium and decreased abundance of Corynebacterium). Our findings suggest that both sebum and the bacterial and fungal microbiomes of the scalp may be involved in the development of AGA.

Prevalence of early-onset androgenetic alopecia and its relation with lifestyle and dietary habits

BACKGROUND

Early-onset androgenetic alopecia (AGA) is the most common cause of alopecia in men under 30 years of age; however, its prevalence and non-genetic risk factors are not well documented. Our aim was to determine the early-onset AGA prevalence and to evaluate its relationship with lifestyle and dietary habits.

METHODS

This study was conducted on 1507 male university students aged 18-30 years. Students with AGA were grouped as mild and moderate-severe according to the Hamilton-Norwood classification. They were asked to complete a questionnaire regarding information about lifestyle and dietary habits including The Adolescent Food Habits Checklist (AFHC) and International Physical Activity Questionnaire (IPAQ) short form.

RESULTS

The prevalence of early-onset AGA was 19.2 % in the students. Each year over the 18 years age, positive family history, unhealthy vegetable-fruit and red meat consumption, presence of a hair disease apart from AGA and smoking were associated with increased risk for early-onset AGA. The median score of AFHC was lower than those without early-onset AGA which reflects the unhealthy dietary habit. Students with moderate-severe AGA had a higher body mass index and waist circumference than those with mild AGA (p < 0.05).

CONCLUSIONS

In addition to family history, lifestyle and dietary habits have roles in earlyonset AGA. Therefore, regulation of lifestyle and dietary habits may have a possible contribution in the prevention of early-onset AGA.

Efficacy and safety of a new 5% minoxidil formulation in male androgenetic alopecia: A randomized, placebo-controlled, double-blind, noninferiority study

BACKGROUND

Androgenetic alopecia (AGA) is the most common cause of hair loss in men. Topical minoxidil solutions can help to treat AGA but have to be applied continuously to be effective.

OBJECTIVES

A new minoxidil formulation with improved cosmetic characteristics (DC0120, Pierre-Fabre Dermatologie) was tested for noninferiority vs a comparator minoxidil product (ALOSTIL^® , Johnson & Johnson) in stimulating hair growth in men with AGA.

METHODS

Two 10 cm² areas on the scalp of each subject were randomized to receive DC0120, the comparator, or one of their corresponding vehicles, applied twice per day for 16 weeks. Nonvellus target area hair count (TAHC) was measured within treatment areas at baseline (day 1) and after 8 and 16 weeks by digital phototrichogram.

RESULTS

Two hundred and twenty subjects were included and randomized, of which 210 completed the study. The mean change in nonvellus TAHC between baseline and week 16 was +22.0 hairs/cm² (95% CI: 18.1; 25.9) in the DC0120 group and +20.5 hairs/cm² (95% CI: 16.6; 24.4) in the comparator group. The adjusted mean difference in TAHC changes between the two treatments was +1.5 hairs/cm² (95% CI -2.3; 5.2), with the lower 95% confidence interval above the noninferiority threshold of -7 hairs/cm² . This indicated that DC0120 was noninferior to the comparator. Both minoxidil treatments also increased nonvellus TAHC compared to vehicle groups at 8 and 16 weeks. No new safety signals were observed.

CONCLUSIONS

DC0120 was as safe and effective as a similar marketed minoxidil product for stimulating hair growth in men with AGA.

Androgenetic alopecia; drug safety and therapeutic strategies

INTRODUCTION

Androgenetic alopecia (AGA) is a benign condition with variable psychosocial impact, with some individuals adapting well while others needing therapeutic support. Although 5α-reductase inhibitors like finasteride and dutasteride have proven effective in ameliorating AGA, their use/selection is currently a subject of debate.

AREAS COVERED

Treatment of AGA with 5α-reductase inhibitors lead to variable adverse effects and relatively unstable results (therapeutic efficacy ending with treatment cessation), so the choice of optimal therapy is not straightforward. This paper presents a general perspective regarding AGA based on studies listed in PubMed, to better understand/appreciate the opportunity for long term use of medication for a biological condition having non-life threatening implications. Studies focussed on adverse effects suggest that finasteride should be used with caution in AGA, due to considerable and persistent side effects induced in some men. In contrast, efficacy data indicate that dutasteride (a stronger inhibitor) presents superior therapeutic results compared to finasteride.

EXPERT OPINION

This paper argues that finasteride should be preferred to dutasteride in the treatment of AGA. Thus, finasteride preserves important physiological roles of dihydrotestosterone (unrelated to AGA) and, in addition, its adverse effects seem to be (at least in part) predictable.

Comparison of the effects of 665 nm low level diode Laser Hat versus and a combination of 665 nm and 808nm low level diode Laser Scanner of hair growth in androgenic alopecia

BACKGROUND

This study aimed to evaluate the effectiveness of a combined set of low level diode laser scanner (665 nm and 808nm) on hair growth, and assessment of safety and effectiveness of a new laser scanner on hair growth treatment procedure in androgenic alopecia.

METHODS

90 patients (18 to 70 years) with androgenic alopecia were randomized into three groups. The first group (n=30) received 655 nm red light using laser hat, the second group (n=30) received 655 nm red laser plus 808 nm infrared laser using a laser scanner of hair growth device (with the patent number: 77733) and the third group (n=30) received no laser as the control group.

RESULTS

Patients in laser scanner group had better results and showed a higher increase in terminal hair density compared with laser hat group (mean of 9.61 versus 9.16 per cm2). We found significant decrease in terminal hair density from baseline in control group (mean -1.8 per cm2, p<0.0001).

CONCLUSION

Results showed a statistically significant improvement in the laser scanner of the hair growth group compared with laser hat and the control group. The study showed that treatment with new laser devise had a promising result without any observable adverse effects.

Meta-analysis identifies novel risk loci and yields systematic insights into the biology of male-pattern baldness

Male-pattern baldness (MPB) is a common and highly heritable trait characterized by androgen-dependent, progressive hair loss from the scalp. Here, we carry out the largest GWAS meta-analysis of MPB to date, comprising 10,846 early-onset cases and 11,672 controls from eight independent cohorts. We identify 63 MPB-associated loci (P<5 × 10^-8, METAL) of which 23 have not been reported previously. The 63 loci explain ∼39% of the phenotypic variance in MPB and highlight several plausible candidate genes (FGF5, IRF4, DKK2) and pathways (melatonin signalling, adipogenesis) that are likely to be implicated in the key-pathophysiological features of MPB and may represent promising targets for the development of novel therapeutic options. The data provide molecular evidence that rather than being an isolated trait, MPB shares a substantial biological basis with numerous other human phenotypes and may deserve evaluation as an early prognostic marker, for example, for prostate cancer, sudden cardiac arrest and neurodegenerative disorders.

Genetic prediction of male pattern baldness

Male pattern baldness can have substantial psychosocial effects, and it has been phenotypically linked to adverse health outcomes such as prostate cancer and cardiovascular disease. We explored the genetic architecture of the trait using data from over 52,000 male participants of UK Biobank, aged 40-69 years. We identified over 250 independent genetic loci associated with severe hair loss (P<5x10-8). By splitting the cohort into a discovery sample of 40,000 and target sample of 12,000, we developed a prediction algorithm based entirely on common genetic variants that discriminated (AUC = 0.78, sensitivity = 0.74, specificity = 0.69, PPV = 59%, NPV = 82%) those with no hair loss from those with severe hair loss. The results of this study might help identify those at greatest risk of hair loss, and also potential genetic targets for intervention.

Illness perception in patients with androgenetic alopecia and alopecia areata in China

OBJECTIVE

The aim of the present study was to provide more information on the role of illness perception in patients with androgenetic alopecia (AGA) and those with alopecia areata (AA), and to further investigate the relationship of illness perception with psychological disorders and dermatological QoL.

METHODS

The study included 342 patients who were diagnosed with AGA (n=212) or AA (n=130) for the first time at our institution between October 2013 and December 2014. All patients were surveyed before clinical examination by several questionnaires including the Brief Illness Perception, Self-rating Depression Scale, Self-rating Anxiety Scale, and Dermatology Life Quality Index (DLQI).

RESULTS

In the AGA patients, the illness perception and QoL were low, whereas the prevalence of clinical depression and anxiety was higher compared to the AA patients. Illness perception was associated with psychological distress and low QoL in both groups, and some illness perception dimensions were found to be significant predictors of the DLQI scores.

CONCLUSION

Illness perception plays an important role in AGA and AA patients, and is associated with psychological distress and low QoL. The identification of critical components of illness perception in alopecia patients could help to understand alopecia specificities, to design consultations and interventions according to the perception, and to improve physical and mental outcomes as well as QoL in alopecia patients.

Both low circulating insulin-like growth factor-1 and high-density lipoprotein cholesterol are associated with hair loss in middle-aged women

BACKGROUND

Multiple biomarkers have been associated with hair loss in women, but studies have shown inconsistent results.

OBJECTIVES

We investigated the associations between markers of cardiovascular disease risk (e.g. serum lipid levels and hypertension) and ageing [e.g. 25-hydroxyvitamin D and insulin-like growth factor (IGF)] with hair loss in a population of middle-aged women.

METHODS

In a random subgroup of 323 middle-aged women (mean age 61·5 years) from the Leiden Longevity Study, hair loss was graded by three assessors using the Sinclair scale; women with a mean score > 1·5 were classified as cases with hair loss.

RESULTS

Every 1 SD increase in high-density lipoprotein (HDL) cholesterol was associated with a 0·65-times lower risk [95% confidence interval (CI) 0·46-0·91] of hair loss. For IGF-1 the risk was 0·68 times lower (95% CI 0·48-0·97) per 1 SD increase, independently of the other studied variables. Women with both IGF-1 and HDL cholesterol levels below the medians of the study population had a 3·47-times higher risk (95% CI 1·30-9·25) of having hair loss.

CONCLUSIONS

Low HDL cholesterol and IGF-1 were associated with a higher risk of hair loss in women. However, further studies are required to infer causal relationships.

Male pattern baldness and risk of colorectal neoplasia

Background:

Male pattern baldness is positively associated with androgens as well as insulin-like growth factor 1 (IGF-1) and insulin, all of which are implicated in pathogenesis of colorectal neoplasia.

Methods:

From 1992 through 2010, we prospectively followed participants in the Health Professionals Follow-Up Study. Hair pattern at age 45 years was assessed at baseline with five image categories (no baldness, frontal-only baldness, frontal-plus-mild-vertex baldness, frontal-plus-moderate-vertex baldness, and frontal-plus-severe-vertex baldness). Cancer analysis included 32 782 men and used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Restricted to men who underwent at least one endoscopy over the study period, adenoma analysis included 29 770 men and used logistic regressions for clustered data to estimate odds ratios (ORs) and 95% CIs.

Results:

Over the mean follow-up of 15.6 years, 710 cases of colorectal cancer (478 for colon, 152 for rectum, and 80 unknown site) developed. Significantly increased risks associated with frontal-only baldness and frontal-plus-mild-vertex baldness relative to no baldness were observed for colon cancer with respective HR being 1.29 (95% CI, 1.03–1.62) and 1.31 (95% CI, 1.01–1.70). Over the 19-year study period, 3526 cases of colorectal adenoma were detected. Evidence for an increased risk of colorectal adenoma relative to no baldness was significant with frontal-only baldness (OR, 1.16; 95% CI, 1.06–1.26) and borderline insignificant with frontal-plus-severe-vertex baldness (OR, 1.14; 95% CI, 0.98–1.33).

Conclusions:

Subtypes of male pattern baldness at age 45 years were positively associated with colorectal neoplasia. Future studies are warranted to confirm our results and to determine the predictive value of male pattern baldness to identify those at high risk for colorectal neoplasia.

Differential Expression between Human Dermal Papilla Cells from Balding and Non-Balding Scalps Reveals New Candidate Genes for Androgenetic Alopecia

Androgenetic alopecia (AGA) is a common heritable and androgen-dependent hair loss condition in men. Twelve genetic risk loci are known to date, but it is unclear which genes at these loci are relevant for AGA. Dermal papilla cells (DPCs) located in the hair bulb are the main site of androgen activity in the hair follicle. Widely used monolayer-cultured primary DPCs in hair-related studies often lack dermal papilla characteristics. In contrast, immortalized DPCs have high resemblance to intact dermal papilla. We derived immortalized human DPC lines from balding (BAB) and non-balding (BAN) scalp. Both BAB and BAN retained high proportions of dermal papilla signature gene and versican protein expression. We performed expression analysis of BAB and BAN and annotated AGA risk loci with differentially expressed genes. We found evidence for AR but not EDA2R as the candidate gene at the AGA risk locus on chromosome X. Further, our data suggest TWIST1 (twist family basic helix-loop-helix transcription factor 1) and SSPN (sarcospan) to be the functionally relevant AGA genes at the 7p21.1 and 12p12.1 risk loci, respectively. Down-regulated genes in BAB compared to BAN were highly enriched for vasculature-related genes, suggesting that deficiency of DPC from balding scalps in fostering vascularization around the hair follicle may contribute to the development of AGA.

Prediction of male-pattern baldness from genotypes

The global demand for products that effectively prevent the development of male-pattern baldness (MPB) has drastically increased. However, there is currently no established genetic model for the estimation of MPB risk. We conducted a prediction analysis using single-nucleotide polymorphisms (SNPs) identified from previous GWASs of MPB in a total of 2725 German and Dutch males. A logistic regression model considering the genotypes of 25 SNPs from 12 genomic loci demonstrates that early-onset MPB risk is predictable at an accuracy level of 0.74 when 14 SNPs were included in the model, and measured using the area under the receiver-operating characteristic curves (AUC). Considering age as an additional predictor, the model can predict normal MPB status in middle-aged and elderly individuals at a slightly lower accuracy (AUC 0.69-0.71) when 6-11 SNPs were used. A variance partitioning analysis suggests that 55.8% of early-onset MPB genetic liability can be explained by common autosomal SNPs and 23.3% by X-chromosome SNPs. For normal MPB status in elderly individuals, the proportion of explainable variance is lower (42.4% for autosomal and 9.8% for X-chromosome SNPs). The gap between GWAS findings and the variance partitioning results could be explained by a large body of common DNA variants with small effects that will likely be identified in GWAS of increased sample sizes. Although the accuracy obtained here has not reached a clinically desired level, our model was highly informative for up to 19% of Europeans, thus may assist decision making on early MPB intervention actions and in forensic investigations.

Evaluation of DNA variants associated with androgenetic alopecia and their potential to predict male pattern baldness

Androgenetic alopecia, known in men as male pattern baldness (MPB), is a very conspicuous condition that is particularly frequent among European men and thus contributes markedly to variation in physical appearance traits amongst Europeans. Recent studies have revealed multiple genes and polymorphisms to be associated with susceptibility to MPB. In this study, 50 candidate SNPs for androgenetic alopecia were analyzed in order to verify their potential to predict MPB. Significant associations were confirmed for 29 SNPs from chromosomes X, 1, 5, 7, 18 and 20. A simple 5-SNP prediction model and an extended 20-SNP model were developed based on a discovery panel of 305 males from various European populations fitting one of two distinct phenotype categories. The first category consisted of men below 50 years of age with significant baldness and the second; men aged 50 years or older lacking baldness. The simple model comprised the five best predictors: rs5919324 near AR, rs1998076 in the 20p11 region, rs929626 in EBF1, rs12565727 in TARDBP and rs756853 in HDAC9. The extended prediction model added 15 SNPs from five genomic regions that improved overall prevalence-adjusted predictive accuracy measured by area under the receiver characteristic operating curve (AUC). Both models were evaluated for predictive accuracy using a test set of 300 males reflecting the general European population. Applying a 65% probability threshold, high prediction sensitivity of 87.1% but low specificity of 42.4% was obtained in men aged <50 years. In men aged ≥50, prediction sensitivity was slightly lower at 67.7% while specificity reached 90%. Overall, the AUC=0.761 calculated for men at or above 50 years of age indicates these SNPs offer considerable potential for the application of genetic tests to predict MPB patterns, adding a highly informative predictive system to the emerging field of forensic analysis of externally visible characteristics.

The contribution of endogenous and exogenous factors to female alopecia: a study of identical twins

BACKGROUND

In this study, the authors investigated the potential contribution of environmental factors and testosterone levels on androgenic alopecia in women.

METHODS

Ninety-eight identical female twins were recruited from 2009 to 2011. Subjects were asked to complete a comprehensive questionnaire, provide a sputum sample for testosterone analysis, and pose for standardized digital photography. Frontal, temporal, and vertex hair loss were assessed from the photographs using Adobe Photoshop. Hair loss measures were then correlated with survey responses and testosterone levels between twin pairs. Two independent, blinded observers also rated the photographs for hair thinning.

RESULTS

Factors associated with increased frontal hair loss included multiple marriages (p = 0.043); longer sleep duration (p = 0.011); higher severity of stress (p = 0.034); positive smoking history (p = 0.021); higher income (p = 0.023); absence of hat use (p = 0.017); and history of diabetes mellitus (p = 0.023), polycystic ovarian syndrome (p = 0.002), and hypertension (p = 0.001). Factors associated with increased temporal hair loss included divorce or separation (p = 0.034), multiple marriages (p = 0.040), more children (p = 0.005), longer sleep duration (p = 0.006), and history of diabetes mellitus (p = 0.008) and hypertension (p = 0.027). Lack of sun protection (p = 0.020), consuming less caffeine (p = 0.040), history of skin disease (p = 0.048), and lack of exercise (p = 0.012) were associated with increased vertex hair loss. Higher testosterone levels were associated with increased temporal and vertex hair loss patterns (p < 0.039). Increased stress, increased smoking, having more children, and having a history of hypertension and cancer were all associated with increased hair thinning (p < 0.05).

CONCLUSION

This study implicates several environmental risk factors in the pathophysiology of female alopecia.

Androgenetic alopecia: identification of four genetic risk loci and evidence for the contribution of WNT signaling to its etiology

The pathogenesis of androgenetic alopecia (AGA, male-pattern baldness) is driven by androgens, and genetic predisposition is the major prerequisite. Candidate gene and genome-wide association studies have reported that single-nucleotide polymorphisms (SNPs) at eight different genomic loci are associated with AGA development. However, a significant fraction of the overall heritable risk still awaits identification. Furthermore, the understanding of the pathophysiology of AGA is incomplete, and each newly associated locus may provide novel insights into contributing biological pathways. The aim of this study was to identify unknown AGA risk loci by replicating SNPs at the 12 genomic loci that showed suggestive association (5 × 10(-8)<P<10(-5)) with AGA in a recent meta-analysis. We analyzed a replication set comprising 2,759 cases and 2,661 controls of European descent to confirm the association with AGA at these loci. Combined analysis of the replication and the meta-analysis data identified four genome-wide significant risk loci for AGA on chromosomes 2q35, 3q25.1, 5q33.3, and 12p12.1. The strongest association signal was obtained for rs7349332 (P=3.55 × 10(-15)) on chr2q35, which is located intronically in WNT10A. Expression studies in human hair follicle tissue suggest that WNT10A has a functional role in AGA etiology. Thus, our study provides genetic evidence supporting an involvement of WNT signaling in AGA development.

The Danish Twin Registry in the New Millennium

The Danish Twin Registry is the oldest national twin register in the world, initiated in 1954, and, by the end of 2005, contained more than 75,000 twin pairs born in the between 1870 and 2004. The Danish Twin Registry is used as a source for studies on the genetic influence on normal variation in clinical parameters associated with the metabolic syndrome and cardiovascular diseases, clinical studies of specific diseases, and aging and age-related health problems. The combination of survey data, clinical data and linkage to national health-related registers enables follow-up studies of both the general twin population and twins from clinical studies. This paper summarizes the newest extension of the register and gives examples of new developments and phenotypes studied.

Why some women look young for their age

The desire of many to look young for their age has led to the establishment of a large cosmetics industry. However, the features of appearance that primarily determine how old women look for their age and whether genetic or environmental factors predominately influence such features are largely unknown. We studied the facial appearance of 102 pairs of female Danish twins aged 59 to 81 as well as 162 British females aged 45 to 75. Skin wrinkling, hair graying and lip height were significantly and independently associated with how old the women looked for their age. The appearance of facial sun-damage was also found to be significantly correlated to how old women look for their age and was primarily due to its commonality with the appearance of skin wrinkles. There was also considerable variation in the perceived age data that was unaccounted for. Composite facial images created from women who looked young or old for their age indicated that the structure of subcutaneous tissue was partly responsible. Heritability analyses of the appearance features revealed that perceived age, pigmented age spots, skin wrinkles and the appearance of sun-damage were influenced more or less equally by genetic and environmental factors. Hair graying, recession of hair from the forehead and lip height were influenced mainly by genetic factors whereas environmental factors influenced hair thinning. These findings indicate that women who look young for their age have large lips, avoid sun-exposure and possess genetic factors that protect against the development of gray hair and skin wrinkles. The findings also demonstrate that perceived age is a better biomarker of skin, hair and facial aging than chronological age.

Genetik der androgenetischen Alopezie

Die androgenetische Alopezie (AGA, erblich- bzw. hormonbedingter Haarausfall [MIM 109200; MIM 300710; MIM 612421]) ist die häufigste Form des Haarverlusts beim Menschen, wobei die Prävalenz stark altersabhängig ist. Im Alter von über 70 Jahren sind über 80% der europäischen Männer betroffen, bei Frauen liegt die AGA-Häufigkeit mit 30–40% deutlich niedriger. Die AGA führt, v. a. bei betroffenen Frauen, zu einer erheblichen psychologischen Belastung und entfaltet dabei Krankheitswert. Der Haarverlust geht auf einen veränderten Haarzyklus und eine Miniaturisierung des Haarfollikels zurück. Die Pathogenese ist androgenabhängig, und die genetische Anlage ist wesentliche Voraussetzung für den Phänotyp. In mehreren Studien konnten der Androgenrezeptor-/Ektodysplasin-A2-Rezeptor(EDA2R)-Locus auf dem X-Chromosom als stärkster beitragender Faktor und durch genomweite Assoziationsuntersuchungen ein weiterer Locus auf Chromosom 20p11 identifiziert werden. Das zum Assoziationssignal nächstgelegene in der Kopfhaut exprimierte Gen ist „paired box 1“ (PAX1). Zwischen PAX1 und dem Androgensignalweg gibt es keine offensichtliche Verbindung, jedoch sind die dem Assoziationssignal auf Chromosom 20p11 zugrunde liegenden pathophysiologischen Prozesse noch nicht geklärt. Bis heute ermöglichen die zur Verfügung stehenden medikamentösen Therapien der AGA bestenfalls ein Aufhalten des Haarverlusts. Mit der Identifizierung der AGA-assoziierten Gene und der Aufklärung ihrer Funktionen wird man die biologischen Ursachen der AGA schrittweise erschließen. Damit ist die Hoffnung auf die Entwicklung neuer Therapien verbunden.

Perceived age as a biomarker of ageing: a clinical methodology

In a previous field-based study, how old one looks for one's age (perceived age) was found to be predictive of mortality in elderly individuals. In conjunction, perceived age is of relevance and interest to the layperson. Here, a clinical methodology for generating perceived age as a biomarker of facial ageing is detailed. The methodology utilises facial photographs of subjects to present images to large numbers of age assessors who are primarily nationals of the country of study origin. In five observational studies in five different countries involving 874 female subjects it was found that subject age and assessor gender, nationality, age and ageing expertise had little effect on the perceived age data generated. However, increasing the numbers of age assessors up to 50 substantially increased the reproducibility of the mean perceived age for an image and a minimum of 10 assessors were required to give reproducible data. This methodology was also compared to a methodology that utilises passport-type photographs of subjects typically taken in field studies. Although the perceived age data from the two types of images were more similar to each other than to chronological age, there was a marked difference between the two sets of data. Therefore, to allow meaningful comparisons across perceived age studies, the same type of image should be used for the generation of perceived age. In conclusion, the methodology detailed here has demonstrated that perceived age can be a reproducible measure when large numbers of adult age assessors are used and can be utilised globally in studies to investigate facial ageing.

Genome-wide scan and fine-mapping linkage study of androgenetic alopecia reveals a locus on chromosome 3q26

Androgenetic alopecia (AGA, male pattern baldness) is the most common form of hair loss. The origin of AGA is genetic, with the X chromosome located androgen receptor gene (AR) being the only risk gene identified to date. We present the results of a genome-wide linkage study of 95 families and linkage fine mapping of the 3q21-q29, 11q14-q25, 18p11-q23, and 19p13-q13 regions in an extended sample of 125 families of German descent. The locus with strongest evidence for linkage was mapped to 3q26 with a nonparametric linkage (NPL) score of 3.97 (empirical p value = 0.00055). This is the first step toward the identification of new susceptibility genes in AGA, a process which will provide important insights into the molecular and cellular basis of scalp hair loss.