Study Links Life’s Crucial 9 To Female Infertility, But Predictive Power Remains Limited

A recent study published in Scientific Reports examined the relationship between Life’s Crucial 9 (LC9) and female infertility. Female infertility, a widespread reproductive issue, has increased by over 56 million cases globally in the last three decades, according to the Global Burden of Disease (GBD) study. The prevalence is expected to rise in the next decade. Infertility can cause emotional distress and may be associated with gynecologic cancers, metabolic disorders, and heart disease.

Understanding the risk factors behind infertility is crucial for prevention and improving reproductive health. Life’s Essential 8 (LE8), a tool developed by the American Heart Association to assess cardiovascular health, served as a base for LC9. LC9 adds a mental health component, linking it to all-cause mortality and cardiovascular health. However, LC9’s predictive power over LE8 is limited.

About the Study

The study aimed to assess the connection between female infertility and LC9 by analyzing data from the National Health and Nutrition Examination Surveys (2013–2018). Participants excluded from the study were those not of reproductive age or with missing data. LE8 is based on four health behaviors—sleep health, physical activity, diet quality, and nicotine exposure—and four health factors, including body mass index (BMI), blood pressure, glucose levels, and lipids.

The Healthy Eating Index (HEI)-2015 measured diet quality, while sleep health, physical activity, and nicotine use were self-reported. Blood glucose scores were derived from glycated hemoglobin, fasting glucose, or a diabetes history. Blood lipid scores came from serum levels of non-high-density lipoprotein (HDL) cholesterol. Depression was assessed using the Patient Health Questionnaire-9 (PHQ-9).

The LC9 score averaged the LE8 components and the depression score, scaled from 0 to 100. Infertility data were self-reported through the Reproductive Health Questionnaire. Covariates included age, ethnicity, education, marital status, income, alcohol use, and health history, such as pelvic inflammatory disease (PID) and birth control pill use.

Researchers used multivariable logistic regression models to examine the link between infertility and LC9, both unadjusted and fully adjusted. They also used restricted cubic splines to analyze nonlinear associations and a receiver operating characteristic (ROC) curve to assess whether LC9 improved upon LE8 in predicting infertility.

Key Findings

The study included 2,088 females, averaging 32.6 years of age. About 14% of participants were infertile. Those with infertility were more likely to be older, non-Hispanic White, and not single. Infertile women had lower LE8 and LC9 scores compared to those without infertility. As LC9 scores increased, women tended to be younger, non-Hispanic White, not infertile, and free from PID. They also tended to drink less alcohol and had later ages of menarche.

In the fully adjusted model, a 10-point increase in LC9 reduced the odds of infertility by more than 21%. Similarly, a 10-point increase in LE8 lowered the odds by nearly 18%. Both LE8 and LC9 showed negative linear associations with infertility. Notably, higher scores for BMI, sleep health, blood glucose, and depression were linked to a lower risk of infertility. However, diet quality, physical activity, nicotine exposure, blood lipids, and blood pressure were not significantly associated with infertility.

Ethnicity and age played key roles. The connection between LC9 and infertility was more pronounced in Mexican American women and those under 35. ROC curve analysis revealed that LC9 and LE8 had comparable predictive abilities for infertility, with modest area under the curve (AUC) values of 0.594 and 0.590, respectively, indicating limited predictive utility.

Conclusion

The study highlights that both LE8 and LC9 are inversely associated with female infertility, particularly in terms of depression, blood glucose, BMI, and sleep health. However, LC9 did not offer significant advantages over LE8 in predicting infertility. The findings suggest that adding a depression score to LE8 may not be necessary for infertility prediction, despite depression’s link to infertility. The overlap between depression and other cardiovascular risk factors could reduce its predictive value.

The authors suggest that future research should explore LC9’s impact in other health areas, especially among young women and underrepresented ethnic groups, and investigate interventions targeting modifiable LC9 factors such as sleep and mental health. Limitations of the study include its cross-sectional nature, reliance on self-reported data, and the inability to establish causality.