Here are two recent references on lowering of age at menarche. Both point
to better and even "more than adequate" nutrition (obesity) as being the
major cause.
>UI - 99347448
>AU - Wattigney WA
>AU - Srinivasan SR
>AU - Chen W
>AU - Greenlund KJ
>AU - Berenson GS
>IN - Tulane Center for Cardiovascular Health, Tulane School of Public
> Health & Tropical Medicine, New Orleans, Louisiana 70112-2824, USA.
>TI - Secular trend of earlier onset of menarche with increasing obesity
> in black and white girls: the Bogalusa Heart Study.
>SO - Ethnicity & Disease 1999 Spring-Summer;9(2):181-9
>AB - Secular trends in onset of menarche and obesity were examined 14
> years apart in two biracial (black-white) cohorts of girls aged 8 to
> 17 under study for cardiovascular risk. The first cohort (N=1,190,
> 64% white) was examined in 1978-1979, the second (N=1,164, 57%
> white) in 1992-1994. The second cohort was heavier in terms of body
> weight and Rohrer index (weight/height3) than the first (P<0.001),
> except among black girls aged 12 to 13 years. Subscapular skinfold
> thickness increased in the second cohort of all ages (P<0.0001),
> while increases in triceps skinfold were less marked. The onset of
> menarche occurred at an earlier age in the second cohort compared
> with the first cohort (P<0.0001), both in black girls (11.4+/-1.3 vs
> 12.3+/-1.4 years) and white girls (11.5+/-1.3 vs 12.3+/-1.3 years).
> Furthermore, twice as many girls in the second cohort had reached
> menarche by ages younger than 12 years (P<0.001). All of these
> obesity measures were significantly associated with the age of
> menarche in both cohorts (P<0.001) adjusting for height, race and
> age at examination. These results suggest that this secular trend
> toward increasing frequency of early onset of menarche may be the
> result of increasing obesity noted in girls of both races. Since
> increases in body fatness and related early onset of menarche are
> risk factors for disorders in adult life including cardiovascular
> disease and breast cancer, the secular trend in the increasing
> incidence of obesity throughout the United States is becoming a
> major public health problem.
>LG - English
>
>2
>UI - 99266197
>AU - Graham MJ
>AU - Larsen U
>AU - Xu X
>IN - Department of Environmental Health, Harvard School of Public Health,
> Boston, Massachusetts 02115, USA.
>TI - Secular trend in age at menarche in China: a case study of two rural
> counties in Anhui Province.
>SO - Journal of Biosocial Science 1999 Apr;31(2):257-67
>AB - There is increasing evidence that age at menarche has decreased in
> Europe and the United States during the last century and in Japan
> over the last several decades. Data from a community-based survey
> conducted in two rural counties of Anhui Province in China indicate
> a similar, downward secular trend in age at menarche for Chinese
> women. The present study shows the mean age at menarche decreased by
> 2.8 years, from 16.5 to 13.7, over an approximate 40-year time
> interval. This rapid decrease in age at menarche may partly be due
> to better nutrition and living standards reflected by the improved
> socioeconomic standards experienced in China over the past few
> decades. To test this hypothesis, a number of determinants of age at
> menarche were assessed; year of birth, literacy status, county of
> residence, amount of physical labour, general health status,
> pesticide exposure before age at menarche, and drinking water source
> were all found to be associated with age at menarche.
>LG - English
>
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