age at menarche in iran

Age at menarche in Iran

S. M. T. Ayatollahi, E. Dowlatabadi and S. A. R. Ayatollahi

School of Public Health, Shiraz University of Medical Sciences, Shiraz, Islamic Republic of Iran

Received 24 April 1999; in revised form 6 February 2001; accepted 23 May 2001

Summary. Background : Age at menarche and its potential associated factors are reportedfor 1862 Shiraz (Southern Iran) secondary school girls taking part in a cross-sectional surveyselected from the four educational districts of the city.Methods: Probit analysis was used to estimate age at menarche, principal component analy-sis (PCA) was applied to analyse socio-economic status (SES). Body mass index (BMI) wasused as an indicator of nutrition.Results: Mean SD age at menarche was 12.91 1.23 years (95% CI: 12.84±12.97). Of allsubjects, 33.7% ®rst menstruated in summer. The highest mean age at menarche was 13.01years in winter. Stress, anxiety and discomfort was seen among 70.3% of subjects atmenarche indicating total or partial ignorance of the menstruation phenomenon. Age atmenarche decreased as SES improved. Menarcheal age was delayed for underweightsubjects.Conclusions: It is concluded that BMI and SES had the most signi®cant e� ects on variationof menarcheal age in a uni®ed statistical model. However, their interaction was found to benot statistically signi®cant.

1. IntroductionThe most striking event in the whole process of female puberty is undoubtedly the

onset of menstruation (Dewhurst 1983). The age at which girls start menstruating isan important factor in health planning and is known to be in¯uenced by geneticfactors (Eveleth and Tanner 1976), by environmental conditions (Saar, Shalev, Dalalet al. 1988), by body size and physique (Sharma et al. 1988, Sharma 1990,Georgiadis, Mantzoros, Evagelopolou et al. 1997, Fakeye 1985) by socio-economicvariables (Roberts, Danskin and Chinn 1975), and by level of education (MacMahon1973). Manniche (1983) calculated age at menarche for mid 19th century inDenmark using Nicolai Edvard Ravn’s data. Since then many authors used di� erentmethods to calculate age at menarche at di� erent parts of the world (Malina, Ryanand Bonci 1994, Khan, Schroeder, Martorell et al. 1995).

At present no published data is available on age at menarche in Iran. However,several unpublished manuscripts are available for a few cities based on selected andunrepresentative samples on this subject (Mossadegh Sedighi 1986, Ahadi 1990,Javadi 1995, Lavihim 1996, Mohaddeth Ardekani 1996, Zareian 1996). Therefore,the purpose of this paper is to present the result of a cross-sectional study on age atmenarche and its correlates among secondary school girls in Shiraz, which wasconducted during the academic year 1997±1998 and based on a representativesample of the subjects over the four educational districts of the city.

2. Materials and methodsShiraz, one of the ®ve principal cities of Iran, is the centre of Fars province of

Iran. The city is located 900 km south of Teheran (Iran’s capital) and 100 km northof the Persian Gulf, at an altitude of 1500 m above sea level. It has a pleasant

ANNALS OF HUMAN BIOLOGY, 2002, VOL. 29, NO. 4, 355±362

Annals of Human Biology ISSN 0301±4460 print/ISSN 1464±5033 online # 2002 Taylor & Francis Ltdhttp://www.tandf.co.uk/journals

DOI: 10.1080 /0301446011008681 7

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Mediterranean climate and a population of 1.2 million, of whom 84% are literate(ILM 1998). The city is both the symbol of ancient civilization and the most devel-oped in southern Iran at present. Schooling is compulsory and supported by thecentral government as applied by local education authority.

2.1. DataAdministratively, Shiraz is divided into four educational districts, each with dis-

tinct social, cultural, economic and health characteristics. Since an adequate sam-pling frame of the population was unavailable, a multistage random sampling wasapplied (Lemeshow, Hosmer, Klar et al. 1990). A 10% sample of secondary schools(guidance as well as high schools) was drawn. Within each secondary school andeach class grade a one in ®ve sample of girls was selected using a table of randomnumbers.

Applying this procedure a total of 1862 secondary school girls was selected in the1997±1998 academic year, in a cross-sectional study, representing a 2% sample ofsecondary school girls in the city.

Each subject was interviewed face to face by a member of the research team at theschool in which she studied and a questionnaire was completed for each. The ques-tionnaires included personal data as well as questions concerning their menstruationand its potential correlates. Permission to conduct this survey was sought throughthe research bureau of the education authority of Shiraz. In addition, consent wassought from each subject to follow the code of medical ethics. The girls heights andweights were measured by a trained auxologist of the research team using the tech-niques presented by Cameron (Cameron 1984).

2.2. MethodsProbit analysis (Agresti 1990) was used to estimate age at menarche. A goodness

of ®t test was used to evaluate the probit model by computing À2 = (residual)/nipi…1 pi† with g 2 degrees of freedom, where ni is the number of girls in each agegroup, pi is the proportion of menstruating girls with age xi and g is the number ofage groups.

Principal component analysis (Jolli� e 1986, Krazanowski 1988) was applied toreduce numerous interrelated socio-economic variables under study to the compon-ents independent from each other to allow interpretations that would not ordinarilyresult. GLIM analysis (Aitkin, Anderson, Francis et al. 1992) also was applied tomodel the menarche data. The Statistical Package for the Social Sciences (SPSS) andGLIM (GLIM4 1992) software were used for calculations.

3. ResultsTable 1 presents the number and the proportion of menstruating girls at every 0.5

year interval and their expected number after ®tting a probit model. A test of good-ness of ®t con®rmed the appropriateness of the probit model employed. Mean (SD)of age at menarche based on probit model was then estimated as 12.91 (1.23) yearswith 95% con®dence intervals (95% CI: 12.84±12.98).

The monthly distribution of menarche in the sample di� ers from the expectedone (table 2). Three peaks of frequency in the ®rst and third spring months andthird summer month are followed by sharp drops in the second months of spring

356 S. M. T. Ayatollahi et al.

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and autumn. Frequencies are also higher than expected in the ®rst and secondsummer months and lower in the second spring month as well as September to

March. No signi®cant di� erences in age at menarche were observed according toseason of birth.

Mean menarcheal age varies signi®cantly according to the season at which

menarche occurs (table 3). The subjects who experienced menarche in spring hadthe lowest age at menarche; this increased in girls who menstruated in summer and

autumn, and shows the highest value in girls who menstruated in winter. The sea-sonal pattern of menarcheal age was di� erent from that in Europe as they had lowest

value in winter and highest value highest value in autumn, which is an increasingpattern from winter to autumn (Gueresi 1997). Only six menstruating girls (0.5%)could not recall their menstrual season exactly.

Age at menarche in Iran 357

Table 1. Number (%) of menstruating girls at every 0.5 year interval and their expected number after®tting a probit model.

Total Number Percent ExpectedAge group* number menstruating menstruating number

11 60 5 8.3 5.011.5 157 20 12.7 27.612 131 38 29.0 37.012.5 253 112 44.3 109.113 135 86 63.7 79.813.5 253 187 73.9 186.414 203 179 88.2 172.514.5 148 131 88.5 136.915 173 168 97.1 167.315.5 30 29 96.7 29.616 172 170 98.8 171.316.5‡ 147 147 100.0 146.8

Total 1862 1272 68.3 1272

Note: *Age groups 11, 11.5, etc. signify 11±11.49, 11.50±11.99, etc., respectively.À2 ˆ 12:70, d.f. ˆ10, p ˆ0.24 (non signi®cant).

Table 2. Monthly distribution of menarche in the examined sample.

Observed Percent Expected ContributionMonth* frequency observed frequency to chi-square

Farvardin 116 12.0 81.8 14.3Ordibehesht 42 4.4 81.8 19.4Khordad 113 11.7 81.8 11.9Tir 95 9.9 81.8 2.1Mordad 90 9.3 81.8 0.8Shahrivar 104 10.8 81.8 6.0Mehr 77 8.0 79.2 0.1Aban 39 4.0 79.2 20.4Azar 66 6.9 79.2 2.2Dey 63 6.5 79.2 3.3Bahman 60 6.2 79.2 4.7Esfand 98 10.2 76.2 6.2

Total 963y 100.0 963 91.4‡

* Iran calendar starts from 21 of March.y 309 menstruating girls could not recall their menarche months.‡ d:f : ˆ 11, p ˆ 0:000.

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A total of 893 (70.3%) menstruating girls had experienced anxiety and discomfort

at the onset of menstruation, while nearly 57 (4.5%) had pleasant feelings and 318

(25.5%) remained indi� erent. Only four menstruating girls could not recall their

feelings at menarche. The high percentage of girls feeling discomfort may be a

re¯ection of cultural background of shyness ruling the girls’ manner.The girls’ knowledge of menstruation as a phenomenon was evaluated by seven

questions incorporated in the questionnaire. About half of secondary school girls

(menstruating as well as non menstruating) answered ®ve to seven questions cor-rectly, whose knowledge was considered as satisfactory, while the other half had

unsatisfactory knowledge concerning this crucial matter. Almost 12% of them were

totally ignorant (table 4). The subjects were asked to identify the ®rst-hand source of

their knowledge regarding menstruation. Only 1348 girls (72.4% of subjects) pro-vided information on the item. Of this ®gure, 529 (39.2%) girls identi®ed mothers,

another 517 girls (38.4%) cited health teachers, while 104 (7.7%) sisters, 97 (7.2%)

cited friends and 74 (5.5%) cited relatives as ®rst-hand sources on menstrual knowl-

edge. Mass media and other sources had minimal impact and only 28 (2%) of girls

identi®ed them as their source of knowledge.Body mass index (BMI), which is de®ned as (weight/height2) in metric units (kg/

m2) (Garrow 1983, Rosenbaum et al. 1988), was signi®cantly associated with

menarcheal age … p ˆ 0:000†. Underweight delays menarche by about 3 monthsand 3 weeks, while overweight and obesity promote it by 3 months plus 1 week

and 4 months plus 3 weeks, respectively, from normal weight girls (table 5). An

index of socio-economic status (SES) was modelled as a linear combination of

parents education (FE and ME for fathers and mothers education, respectively),previous and present family social class (SC1 and SC2) based on fathers occupation.


Table 3. Age at menarche (years) according to season of menarche.

Season Number Percent Mean SD

Spring 337 26.6 12.45(a) 1.20Summer 426 33.7 12.59(a) 1.13Autumn 213 16.8 12.78(b) 1.19Winter 290 22.9 13.01(c) 1.14Total 1266 100.0 12.91 1.23

ANOVA: F ˆ11.62; p ˆ0.00; (a) seasons signi®cantly di� erent from (b) and(c) seasons using Duncan multiple comparison tests.

Table 4. Number and percentage of high school girls according to theirknowledge on menstruation phenomenon.

Mark Knowledge grade Number Percent

0 none 217 11.61 minimal 64 3.42 very poor 102 5.53 poor 209 11.24 fair 380 20.35 good 480 25.76 very good 312 16.77 excellent 104 5.6

Total 1868 100.0

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Parents education levels were categorized and valued as 0 ˆ illiterate, 1 ˆread andwrite, 2 ˆelementary school, 3 ˆsecondary school, 4 ˆhigher education. Social classwas categorized and given values as 0 ˆ jobless, 1 ˆunskilled manual, 2 ˆsemi-skilled manual, 3 ˆskilled manual, 4 ˆclerical, 5 ˆmanagerial, 6 ˆprofessional.GLIM analysis was used to combine these two types of variables properly. Usingprincipal component analysis (PCA) SES was given by ®rst principal component(PC) as:

SES ˆ 0:3…FE ‡ ME ‡ SC1 ‡ SC2†

and explained 67% of variation, which was a suitable index for evaluating SES.Mean age at menarche by SES is presented in table 6. As can be seen, nearly a

quarter of girls were from poor families, whose age at menarche were signi®cantlydi� erent from girls of middle and higher classes … p ˆ 0:000†. Therefore, an indirectrelationship between age at menarche and SES was found.

The di� erence between observed and estimated mean age at menarche for eachBMI and SES category ranges between half a week and 3 weeks for underweight andnormal weight classes irrespective of the SES class that she belongs to. This wouldincrease to 2 months plus 2 weeks for overweight to 5 months plus 2 weeks for obesegirls. Caution should be taken when estimating age at menarche for the overweightgroups as the discrepancies between observed and estimated age at menarche may bestriking and unrealistic. BMI and SES are identi®ed as two in¯uencing factors onmenarcheal age of high school girls which should be taken into account as ourproposed model considered.

4. DiscussionAge at menarche in this study is less than most African, and Asian studies

but greater than most European and North American countries, which may re¯ect


Table 5. Age at menarche of high school girls according to BMI.

BMI class BMI range Number Percent Mean SD

Underweight BMI < 20 634 49.8 12.92(a) 1.11Normal 20 4 BMI < 25 524 41.2 12.62(b) 1.16Overweight 25 4 BMI 4 30 105 8.3 12.35(c) 1.45Obese BMI>30 9 0.7 12.23(c) 1.04

Total 1272 100.0 12.91 1.23

ANOVA: F ˆ15.6, p ˆ0.000, (c) BMI classes signi®cantly di� erent from (a) and (b) BMI classes usingDuncan multiple comparison tests.

Table 6. Age at menarche of high school girls by SES.

SES Number Percent Mean age

Low class 291 23.8 12.96(a)Middle class 656 53.6 12.64(b)High class 277 22.6 12.52(b)

Total 1224 100.0 12.69

ANOVA: F ˆ10.5, p ˆ0.000, (b) SES classes signi®cantly di� erentfrom (a) SES classes using Duncan multiple comparison tests.

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environmental as well as genetic factors a� ecting high school girls in Iran. Themethods of collecting and analysing data in di� erent studies had not been thesame. Therefore, comparing mean ages at menarche in di� erent studies should bedone cautiously. Table 7 compares mean age at menarche in Iran for unpublishedstudies.

Age at menarche in this study was di� erently estimated from other studies in Iran.First, we used a representative sample from the population under study. Secondly,secondary school girls were interviewed in a face to face manner by a female trained

member of the research team in a private room at each school allocated for thispurpose and the subjects were totally aware of the objectives of the study. Thirdly,probit analysis was used to estimate age at menarche, which takes all subjects intoaccount. The regression model and its associated goodness of ®t test justify applica-tion of this model for our data, while other studies used age of menstruating girls.So, the results of this study were better validated and more reliable than other studiesand can be generalized to the urban population of Iran given that demographicstructure of our data is similar that of the urban population. As schooling rate inhigh school girls was 92% (IPHD 1998) generalization of the results to 8% of nonschool attenders should be taken cautiously.

The statistical methods used here to model the data well. PCA provides a suitableindex to study SES, which is a very di� cult factor to quantify appropriately. These

results may be used as a guidance for health promotion in girls of menstruating ages.Koo et al. (1997) reported that in Canadian females only 59.1% could recall theirmenarche with exact month and year. Some 76% of respondents in this study were

able to recall their menarche with the exact month and year, which is comparable toan study on university athletes of USA (Malina et al. 1994), indicating a good rate ofawareness in the menstruating girls in Iran.

In the sample examined in the present study, menarche occurs more frequentlythan expected in coincidence with school vacations (about 4 months from June tomid September, and 15 days from 21 March celebrating Iranian new year holidays),while an abrupt decrease in frequency is observed with return-to-school activities.

If the eventuality of bias in recallÐdue to a tendency to associate menarche withevents easy to remember, such as festivalsÐmay be excluded, one may suppose thatstress associated with school activity could have an inhibiting e� ect on puberty,which on the contrary would appear favoured in periods of greater relaxation. Inthis regard it is to be noted that, on the whole, as time passes from the beginning ofthe holiday, so menarche frequency increases. This hypothesis is in agreement withthe results of some other studies in European (Gueresi 1997 in Italy, Kantero andWidholm 1971 in Finland, Bergsten-Brucefors 1974 in Sweden as quoted by


Table 7. Comparison of mean age at menarche in Iran.

City n Mean SD Author*

Abhar 980 12.97 Ð Ahadi 1990Ardabil 96 12.77 Ð Javadi 1995Teheran 90 12.48 1.12 Mosaddegh Sedghi 1986Shiraz 2074 13.05 1.25 Zareian 1996Shiraz 2000 13.17 0.99 Mohaddeth Ardekan 1996Yasouj 437 12.69 1.27 Lavihim 1996

* See references.

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Bruntland and Liestol 1982 in Norway) as well as non-European countries(Balasuria and Fernando Malcolm 1988 in Sri Lanka, Nakamura, Shimura,Nonaka et al. 1986 in Japan, Shakir 1974 in Iraq) except for the Iranian new yearholidays.

AcknowledgementsThis work was supported by grant number 76-412 from Shiraz University of

Medical Sciences Research Council. The authors also thank Dr Minoo Robati,gynaecologist and obstetrician, for her valuable comments. We are grateful to thereferees whose thoughtful comments greatly improved this paper.

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25±41.Eveleth, P. B., and Tanner, J. M., 1976, Worldwide Variation in Human Growth (Cambridge: Cambridge

University Press), pp. 213±219.Fakeye, O., 1985, The interrelationships between age, physical measurements and body composition.

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679±708.Georgiadis, E., Mantzoros, C. S., Evagelopolou , C., and Spentzos, D., 1997, Adult height and

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M. Green and C. Payne (Oxford: Oxford University Press).ILM, 1998, Iran Literacy Movement Report [Persian].IPHD, 1998, Perspective of Health and Development in the Islamic Republic of Iran [Persian]. Ministry of

Health and Medical Education Publications, Teheran.Javadi, F., 1995, Age at menarche in relation to weight, height and physical activities of school girls of

Ardabil. MS Thesis [in Persian], Teheran University of Medical Sciences, Teheran (unpublished).Jolliffe, I. T., 1986, Principal Component Analysis (New York: Spinger).Kantero, R. L., and Widholm, O., 1971, The age of menarche in Finnish girls in 1969. Acta Obstetrico

etGynecologica Scandinavica, Supplement, 14, 7±18.Khan, A. D., Schroeder, D. G., Martorell, R., and Riverva, J. A., 1995, Age at menarche and

nutritional supplementation. American Journal of Nutrition, 125, 1090±1096.Koo, M. M., and Rohan, T. E., 1997, Accuracy of short-term recall of age at menarche. Annals of Human

Biology, 24, 61±64.Krzanowski, W. J., 1988, Principles of Multivariate Analysis: a User’s Perspective (Oxford: Oxford

Science Publications).Lavihim, F., 1996, Factors a� ecting age at menarche in Yasouj guidance schools. MS thesis [in Persian],

Isfahan University of Medical Sciences, Isfahan.Lemeshow, S., Hosmer D. W. Jr, Klar, J., and Lwanga, S. K., 1990, Adequacy of Sample Size in

Health Sciences (New York: John Wiley and Sons).MacMahon, B., 1973, Age at menarche: United States Department of Health, Education and Welfare

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Address for correspondence: S. M. T. Ayatollahi, Department of Biostatistics and Epidemiology,P.O. Box 71345-1874 , School of Public Health, Shiraz University of Medical Sciences, Shiraz, IslamicRepublic of Iran.

Zusammenfassung. Es wird berichtet uÈ ber das Alter der Menarche und die damit moÈ glichen assoziiertenFaktoren. In einer Querschnittsstudie wurden 1862 MaÈ dchen, welche eine Oberschule besuchten, aus vierBildungsbezirken aus Shiraz (SuÈ diran) ausgewaÈ hlt.Mittels einer Probit-Analyse wurde das Alter zum Eintritt der Menarche geschaÈ tzt; eineHauptkomponentenanalyse wurde angewandt, um den soziooÈ konomischen Status (SES) zu analysieren.Als Indikator zur De®nition der ErnaÈ hrung wurde der Body-Mass-Index (BMI) verwendet.Mittelwert Standardabweichung fuÈ r das Alter beim Eintritt der Menarche waren 12.91 1.23 Jahre(95% CI: 12.84±12.97). 33.7% aller Probandinnen hatten ihre erste Menstruation im Sommer. DashoÈ chste mittlere Menarchealter lag im Winter und betrug 13.01 Jahre. Bei 70.3% der MaÈ dchen, beiwelchen eine totale oder teilweise Unkenntnis uÈ ber das PhaÈ nomen der Menstruation zu erkennen war,bestand Stress, Angst und Unbehagen vor diesem Ereignis. Das Alter der Menarche sank mit demAnsteigen des SES. Das Menarchealter war bei untergewichtigen Personen verzoÈ gert.Es wird geschlussfolgert, dass BMI und SES in einem vereinheitlichten statistischen Modell die groÈ ûtensigni®kanten E� ekte auf die Schwankung des Menarchealters haben. Aber die gefundene Interaktion warnicht statistisch signi®kant.

ReÂ sumeÂ . ArrieÁre-plan: L’aÃ ge aux premieÁ res reÁ gles et les facteurs qui lui sont potentiellement associeÂ s, sontdeÂ crits dans le cadre d’une eÂ tude transversale impliquant 1862 colleÂ giennes de quatre districts scolaires dela ville de Shiraz (Iran).MeÂthodes: L’analyse de probits a eÂ teÂ utiliseÂ e pour estimer l’aÃ ge des premieÁ res reÁ gles, le statut socio-eÂ conomique a eÂ teÂ eÂ valueÂ au moyen d’une analyse en composantes principales et l’indice de masse corpor-elle a eÂ teÂ utiliseÂ comme indicateur de nutrition.ReÂsultats: La moyenne et l’eÂ cart-type de l’aÃ ge aux premieÁ res reÁ gles sont de 12,91 1,23 ans (intervalle decon®ance 12,84±12,97). 33,7% des sujets ont eu leurs premieÁ res menstrues en eÂ teÂ . La moyenne la pluseÂ leveÂ e de l’aÃ ge des premieÁ res reÁ gles est de 13,01ans en hiver. Le stress, l’anxieÂ teÂ et l’inconfort observeÂ s chez70,3% des sujets reÂ gleÂ s indiquait une ignorance partielle ou totale du pheÂ nomeÁ ne de la menstruation. L’aÃ geaux premieÁ res reÁ gles deÂ croõÃ t avec l’ameÂ lioration du statut socio-eÂ conomique. L’aÃ ge aux premieÁ res reÁ gles estretardeÂ pour les sujets maigres.Conclusions: L’indice de masse corporelle et le statut socio-eÂ conomique ont les e� ets les plus signi®catifssur la variation de l’aÃ ge des premieÁ res reÁ gles dans un modeÁ le statistique uni®eÂ . Leur interaction n’apparaõÃ tcependant pas statistiquement signi®cative.


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age at menarche in iran

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