Longitudinal reliability of self-reported age at menarche in adolescent girls: variability across time and setting.

Age at menarche is collected during routine adolescent or adult health care visits, but it is a key variable in social-behavioral as well as clinical research studies. For example, studies focusing on the secular trend of early maturation use age at menarche to describe pubertal differences across cohorts (Chumlea et al., 2003), whereas biobehavioral studies use age at menarche to categorize pubertal timing (e.g., “early”, “on-time”, “late”) (Deardorff, Gonzales, Christopher, Roosa, & Millsap, 2005; Marklein, Negriff, & Dorn, 2009; Mendle, Turkheimer, & Emery, 2007; Obeidallah, Brennan, Brooks-Gunn, & Earls, 2004). Alternatively, clinical studies use age at menarche to describe risk associated with certain diseases as illustrated by literature showing girls with earlier menarche may be at greater risk for cardiovascular disease (Remsberg et al., 2005) or adult breast cancer (Apter, Reinila, & Vihko, 1989; Hamilton & Mack, 2003). On an individual level, age at menarche can provide critical input into clinical decision making, whereas findings from research studies about risks associated with timing of menarche can be used to direct patient care or inform community-wide prevention. With the application of age of menarche for numerous purposes and settings, it is critical to note the dearth of research describing the reliability of age at menarche across time or whether reliability varies across methods of assessment. Age of menarche is a marker that must rely on self-report, or in some cases parent report, since identifying the actual onset objectively would require tracking efforts prior to the event that would be labor intensive and virtually prohibitive. Thus, in the strictest sense, no real “gold standard” exists for determining age at menarche. Using correlations, studies of age at menarche report reliability across as much as 40 years range from .60 to .83(Artaria & Henneberg, 2000; Bergsten-Brucefors, 1976; Damon & Bajema, 1974; Hediger & Stine, 1987; Koo & Rohan, 1997; Koprowski, Coates, & Bernstein, 2001; Livson & McNeill, 1962; Must et al., 2002). However, most of these studies rely on as few as two assessments, a decade or more apart. Correlational studies do not fully address consistency in reports; in turn, they may underestimate the degree of fluctuation in self-reported age at menarche across time. For example, kappa coefficients were reported as low to moderate (e.g., k = .35) when comparisons included an adolescent self-report and then self-report at age 48 (Cooper et al., 2006). Further, there may be some instances in which repeated self-report varies by several months. The resulting error from this methodological influence may be more crucial for certain research questions than others. For example, reports varying by a year may be less important for a study examining an outcome 30–40 years later compared with a longitudinal study categorizing pubertal-age girls into timing categories where the event is more proximal. Such variability was noted by a study of 9–13 year-olds where they were asked their age at menarche by clinician interview and then by questionnaire at baseline, 6- and 12-months later. Reports varied by as much as 18 months across one year (Dorn et al., 1999). As such, different conclusions about timing of age at menarche and its effect on an outcome (e.g., substance use, depression) will be drawn in the absence of a reliable method of assessing age at menarche. To address the gap in the adolescent literature, our aims were to use two methods of assessment (in-person, phone) to determine: 1) the average method reliability of reporting age at menarche across the three years, 2) test-retest reliability of reports between different time points and methods, 3) intraindividual variability of reports, and 4) whether intraindividual variability of reports differed by method or individual characteristics (i.e., race, pubertal timing and gynecological age). The analytic goal was descriptive rather than predictive. Thus, specific hypotheses were not made.