The inverse association between parity and bone health is independent of lifestyle in postmenopausal Chinese women

Association between parity and bone mineral density in postmenopausal women

BACKGROUND

Pregnancy has been considered a risk factor for the development of osteoporosis. Despite much research in this field, the relationship between parity and bone mineral density (BMD) is still controversial. Therefore, we conducted this study to investigate whether there was an association between parity and BMD of the femoral neck and lumbar spine in postmenopausal women.

METHODS

Cross-sectional study was conducted using data from the National Health and Nutrition Examination Survey (NHANES). Three linear regression models, Model 1 (unadjusted), Model 2 (adjusted for age and body mass index (BMI)), and Model 3 (adjusted for all covariates), were established to evaluate the relationship between parity and BMD. In addition, the p value trend of BMD in the different parity groups was mutually verified with the results of multiple regression. Multiple logistic regression models were used to assess the relationship between parity and osteoporosis.

RESULTS

In total, 924 postmenopausal women aged 45-65 years were eligible for this study. After adjustment for potential confounders, women with ≥ 6 parities had significantly lower lumbar spine BMD than women with 1-2 parities (β = - 0.072, 95% CI: - 0.125, - 0.018, P = 0.009). However, there was no correlation between parity and femoral neck BMD in any of the three regression models. Furthermore, ≥ 6 parities were associated with a significantly higher prevalence of lumbar spine osteoporosis compared with 1-2 parities (OR = 3.876, 95% CI: 1.637, 9.175, P = 0.002).

CONCLUSIONS

After adjustment for BMD-related risk factors, ≥ 6 parities were associated with decreased lumbar spine BMD but not femoral neck BMD in postmenopausal women. This suggests that postmenopausal women with high parity are at increased risk of lumbar osteoporotic fractures and should pay more attention to their bone health.

Association of Polymorphisms in Estrogen Receptor Genes (ESR1 and ESR2) with Osteoporosis and Fracture-Involvement of Comorbidities and Epistasis

Single-nucleotide polymorphisms (SNPs) in the ESR1/ESR2 genes play a role in osteoporosis (OP). Our objective was to determine associations of polymorphisms in ESR genes with OP and fracture, SNP-SNP interactions, and involvement of comorbidities. We analyzed 170 Mexican osteoporotic women (FNOP), 173 with hip fracture (HFx), and 210 controls. The SNPs, ESR1 rs2234693CC, rs851982CC and rs1999805AA, were associated with reduced OP risk (odds ratios [ORs] = 0.35, 0.40 and 0.32, respectively; p < 0.05); rs2234693CC was associated with reduced fracture risk (OR = 0.24; p < 0.05). The obese/overweight carriers of rs9340799GG had a lower OP (OR = 0.15, p = 0.016) and fracture (OR = 0.12, p = 0.0057) risk. The rs9479055AA and rs3020404AA hypertensive carriers had a higher OP risk (OR = 5.96, p = 0.032; and OR = 5.29, p = 0.02, respectively). In addition, rs3020404AA had a higher risk of fracture (OR = 4.90, p = 0.045). The rs2228480GG hypertensive carriers had a higher risk of fracture (OR = 6.22, p = 0.0038). We found a synergic relation between the ESR1 rs3020331 and rs1999805 in femoral neck OP and HFx. The rs2234693 (PvuII) and rs9340799 (XbaI) polymorphisms are associated with a high risk forming a haplotype. The epistasis analysis suggests the contribution of both genes (ESR1/ESR2) to the risk of OP and fracture. Epistasis and involvement of obesity and hypertension lead to a significant modification of the risk.