Lifestyle factors associated with histologically derived human ovarian non-growing follicle count in reproductive age women.

STUDY QUESTION: Are lifestyle factors (smoking, BMI, alcohol use and oral contraceptive pill use) associated with the human ovarian reserve as determined by the total ovarian non-growing follicle number? SUMMARY ANSWER: Light to moderate alcohol use was significantly associated with greater ovarian non-growing follicle (NGF) count, whereas other lifestyle factors were not significantly related. WHAT IS KNOWN ALREADY: A single previous investigation has suggested that smoking and alcohol use are associated with lower ovarian follicle density. However, this investigation utilized follicle density as the outcome of interest rather than the estimated total ovarian NGF count. STUDY DESIGN, SIZE, DURATION: This cross-sectional investigation included a convenience sample of premenopausal women from two different academic sites, the University of Washington (n = 37, from 1999-2004) and the University of Oklahoma (n = 73, from 2004-2013), undergoing incidental oophorectomy at the time of hysterectomy (total n = 110, age range 21-52 years). PARTICIPANTS/MATERIALS, SETTING,
METHODS: Prior to undergoing oophorectomy, participants completed detailed questionnaires regarding lifestyle exposures. Following surgery, total ovarian NGF counts were determined with systematic random sampling rules and a validated fractionator/optical dissector technique. Associations between lifestyle factors and log-transformed ovarian follicle counts were determined using multivariable linear regression. MAIN RESULTS AND THE ROLE OF CHANCE: After controlling for age, BMI, oral contraceptive pill (OCP) use, tobacco use and site of collection, cumulative alcohol use (measured in alcoholic drinks per day multiplied by years of drinking) was associated with ovarian NGF count. Women reporting light (>0 to <1 drink-years) and moderate (1-3 drink-years) alcohol use had greater NGF counts (β = 0.75, P = 0.04, and β = 1.00, P = 0.03; light and moderate use, respectively) as compared with non-users. Neither heavier alcohol use (>3 drink-years), BMI, OCP use, nor tobacco use were significantly associated with the ovarian NGF count. Similar patterns of association with moderate cumulative alcohol use were observed when evaluating associations with pre-antral follicles and total follicle counts. LIMITATIONS, REASONS FOR CAUTION: All participants in this convenience sample had a benign indication for hysterectomy, and therefore may not be broadly representative of the population without such an indication. Additionally, lifestyle factors were self-reported, and the sample size of the present investigation limits our ability to detect associations of smaller magnitude. WIDER IMPLICATIONS OF THE
FINDINGS: While our findings are in disagreement with a single investigation that utilized human follicle density as the outcome of interest, they are consistent with many studies investigating the relationship between lifestyle factors and the age of spontaneous menopause. Furthermore, they suggest a mechanism that does not involve accelerated follicular atresia to explain the association between smoking and an earlier age of menopause. STUDY FUNDING/COMPETING INTERESTS: This investigation was funded by NIA R29-HD37360-04 (N.A.K.) and OCAST HR04-115 (K.R.H.) and by the National Institute of General Medical Sciences, Grant 1 U54GM104938 (J.D.P.). There is no conflict of interest.