Bone is living tissue. Throughout life, the body removes small amounts of older bone and replaces them in a process called remodeling. Estrogen helps regulate that balance. As estrogen levels decline during the menopause transition, bone breakdown can outpace replacement for a time, contributing to lower bone mineral density. That biology helps explain a population pattern; it does not determine what will happen to one person.
What the SWAN study found about timing
A multiethnic analysis from the Study of Women’s Health Across the Nation (SWAN) followed 862 women who were premenopausal or in early perimenopause at baseline and later had a dateable final menstrual period. Bone-density loss at the lumbar spine and femoral neck began about a year before the final menstrual period. The rates and total amount of loss were greatest from one year before through two years after it. Loss continued after that window, but at a slower rate in the study.
This is a cohort finding about average bone-density change measured over time. It is not a prediction that every woman will lose bone at the same rate, and bone density is not the same outcome as a fracture. The study cannot calculate an individual’s fracture risk from menopause timing alone.
Why personal risk varies
Age and menopause are only part of the picture. A clinician may also consider a prior fracture, low body weight, a parent’s history of hip fracture, smoking, alcohol use, medicines such as long-term glucocorticoids, and health conditions that affect bone. The combination and significance of these factors differ from person to person. A group average or a menopause stage cannot diagnose osteoporosis or provide an individual fracture forecast.
Prevention is a collection of supports
The Bone Health & Osteoporosis Foundation’s clinical guide includes regular weight-bearing and muscle-strengthening activity, adequate calcium and vitamin D, and attention to falls as parts of bone-health and fracture-prevention care. Walking and resistance exercise are examples of different kinds of activity, but the suitable options depend on a person’s health, ability, and circumstances. Exercise and fall-prevention evidence covers different outcomes and does not promise that a particular routine will prevent a fracture.
Nutrition matters too. The guide discusses getting adequate calcium and vitamin D, with needs and supplement decisions depending on age, diet, health, and medicines. A clinician can help assess whether a person’s dietary amount or a supplement is appropriate. These are general prevention topics; what is appropriate varies by circumstance.
Screening depends on age and risk
The U.S. Preventive Services Task Force’s 2025 recommendation advises osteoporosis screening for women 65 and older. It also advises a clinical risk-assessment approach for postmenopausal women younger than 65 who have risk factors, with screening when that assessment indicates increased risk. This guidance does not mean every woman in her 40s or 50s needs a scan. A clinician can consider personal history, risk factors, and other applicable guidance when deciding whether and when screening makes sense.
If you have had a fracture after a minor fall, take a medicine that may affect bone, or have a condition associated with bone loss, those details are useful to raise with a healthcare professional. Screening and prevention decisions should be made in the context of your full health history.
For related context, read the strength conversation women should have earlier and what changes in midlife hormones. The Muscle & Bone section of the Research Library describes the SWAN study population and its limits.
Educational scope: This article provides general information about bone health and menopause research. It cannot diagnose osteoporosis, estimate your individual fracture risk, or replace advice from a healthcare professional.
Source layer
The SWAN cohort describes average bone-density changes in a defined population. The clinical guide and screening recommendation summarize guidance for clinical care; none can diagnose or forecast an individual reader’s risk.
- Longitudinal cohort analysis: Greendale GA, Sowers M, Han W, et al. “Bone mineral density loss in relation to the final menstrual period in a multiethnic cohort: results from the Study of Women’s Health Across the Nation (SWAN).” Journal of Bone and Mineral Research. 2012;27(1):111–118. The analysis included 862 women who were pre- or early perimenopausal at baseline and later had a dateable final menstrual period. Bone-density loss began about one year before that period and was greatest from one year before through two years after it at the lumbar spine and femoral neck. This describes timing in the cohort, not an individual fracture forecast. PubMed, PMID 21976317.
- U.S. clinical practice guide: LeBoff MS, Greenspan SL, Insogna KL, et al. “The clinician’s guide to prevention and treatment of osteoporosis.” Osteoporosis International. 2022;33(10):2049–2102. This Bone Health & Osteoporosis Foundation guide is written for clinicians caring for adults at risk of osteoporosis and fracture. It covers bone biology, fracture-risk assessment, weight-bearing and muscle-strengthening activity, adequate calcium and vitamin D, and fall prevention as parts of care. It is clinical guidance, not a plan for every reader. Full text, PMID 35478046.
- U.S. Preventive Services Task Force recommendation: “Screening for Osteoporosis to Prevent Fractures.” Final recommendation published January 14, 2025. For women 65 years or older, the USPSTF recommends screening. For postmenopausal women younger than 65, it recommends a two-step approach: identify risk factors, then use clinical risk assessment to determine whether screening is appropriate. This is population-level preventive guidance and does not replace individualized clinical judgment. USPSTF recommendation.
Where to read next
Continue with the strength conversation to have earlier and hormone changes in midlife. The Bone & Strength guide offers a broader view of scans, strength, balance, and function; the Menopause guide covers the wider transition. For study details, visit the Research Library’s Muscle & Bone section.