Nongenetic Determinants of Age at Menarche: A Systematic Review

Table 1

Strengths, weaknesses, opportunities, and threats for studies on the nongenetic factors affecting AAM.

Strengths	Weaknesses
(1) The large number of studies for the last two decades identified many potential environmental determinants of AAM; (2) Large volume of data on physiology of puberty and reproduction is available; (3) Advanced bioinformatics methods and powerful computer technologies make it possible to analyse large data set of data; (4) Critical mass in reproductive epidemiology, physiology, and endocrinology	(1) Aetiology of menarche is largely unknown; (2) The results of different studies are often inconsistent; (3) Data from non-Caucasian populations are limited; (4) It is difficult to determine the effect of any single factor; (5) There are many potentially important but yet unknown factors, which may confound the results; (6) Data about gene-environment interactions and their effect on AAM are scarce; (7) Persistent migration processes worldwide make it difficult to recruit ethnically homogenous cohorts; (8) Continuous variation of many environmental factors makes it difficult to determine the effect size; (9) Animal models are often inappropriate for studying an effect of many environmental factors on AAM
Opportunities	Threats
(1) Use homogenous ethnic populations for epidemiological studies of AAM; (2) More emphasis on the exposure to the environmental factors during prenatal and early childhood period, during which their effect is more pronounced; (3) Collaborative efforts of research groups from different countries will help to increase efficiency of the epidemiological studies of AAM; (4) Implementation of the results in preventive medicine and public health management.	(1) Potential exposure to new factors (e.g., chemicals) with an unknown effect on the female reproductive system; (2) The number of environmental factors affecting AAM may be very large; (3) Several generations are often needed to determine a consistent cause-effect relationship between environmental determinants and AAM; (4) Epidemiological studies in the low-income countries are difficult to conduct due to the lack of sufficient funding; (5) Methodology of the result application in public health management is still not well developed