24-hour movement behaviours and cardiometabolic markers in women with polycystic ovary syndrome (PCOS): a compositional data analysis.

Study question: Are 24-h movement composition and time reallocations between the movement behaviours (moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), sedentary behaviour (SB), and sleep) differentially associated with cardiometabolic markers in women with polycystic ovary syndrome (PCOS) relative to women without PCOS?

Summary answer: There was no difference in 24-h movement composition between the groups, although among women without PCOS, reducing SB time while increasing either MVPA or LPA time was associated with beneficial differences in cardiometabolic markers, whereas in women with PCOS beneficial differences were observed only when SB time was replaced with MVPA.

What is known already: Women with PCOS display lower levels of physical activity, higher sedentary time, and less total sleep than women without the syndrome. Exercise interventions among women with PCOS have shown improvements in body composition and insulin sensitivity, while the findings regarding blood pressure, insulin resistance, and lipid profiles are contradictory.

Study design, size, duration: This study was part of a prospective, general population-based Northern Finland Birth Cohort 1966 (NFBC1966) (n = 5889 women). At the 31-year and 46-year follow-up, data collection was performed through postal and clinical examinations, including fasting blood samples and anthropometric measurements. Accelerometer data collection of 14 days (n = 2602 women) and a 2-h oral glucose tolerance test (n = 2780 women) were performed at the 46-year follow-up. Participants were identified as women with or without PCOS at age 31 (n = 1883), and the final study population included those who provided valid accelerometer data at age 46 (n = 857).

Participants/materials, setting, methods: Women with PCOS (n = 192) were identified based on the 2023 International Evidence-based Guideline, while those who exhibited no PCOS features were considered women without PCOS (controls; n = 665). Accelerometer-measured MVPA, LPA, and SB were combined with self-reported sleep to obtain 24-h compositions. Multivariable regression analysis based on compositional data analysis and isotemporal reallocations were performed to investigate the associations between 24-h movement composition and cardiometabolic markers. Isotemporal reallocations were expressed as differences (%Δ) from the sample's mean.

Main results and the role of chance: There was no difference in overall 24-h movement composition between women with PCOS and controls in midlife. The 24-h movement composition was associated with waist circumference, triglycerides, fasting serum insulin, and Homeostatic Model Assessment-insulin resistance (HOMA-IR) in both controls and women with PCOS. Reallocating 15 min from SB to MVPA was associated with favourable differences in cardiometabolic markers in both controls (%Δ range from -1.7 to -4.9) and women with PCOS (%Δ range from -1.9 to -8.6). Reallocating 15 min from SB to LPA was also associated with favourable differences in cardiometabolic markers among controls (%Δ range from -0.5 to -1.6) but not among women with PCOS.

Limitations, reasons for caution: The substitution technique used in this study is theoretical, which can be considered as a limitation. Other limitations of this study are the use of self-reported sleeping time and the difference in the group sample sizes.

Wider implications of the findings: These findings suggest that women with PCOS should be targeted with interventions involving physical activity of at least moderate intensity to improve their cardiometabolic health and underline the importance of developing tailored activity guidelines for women with PCOS.

Study funding/competing interest(s): This study was funded by the Jenny and Antti Wihuri Foundation, Sigrid Juselius Foundation, Novo Nordisk (NNF21OC0070372), Research Council of Finland (315921/2018, 321763/2019, 6GESS 336449), Ministry of Education and Culture of Finland (OKM/54/626/2019, OKM/85/626/2019, OKM/1096/626/2020, OKM/20/626/2022, OKM/76/626/2022, and OKM/68/626/2023), and Roche Diagnostics International Ltd. L.J.M. is supported by a Veski Fellowship. M.Nu. has received funding from Fibrobesity-project, a strategic profiling project at the University of Oulu, which is supported by Research Council of Finland (Profi6 336449). NFBC1966 follow-ups received financial support from University of Oulu (Grant no. 65354, 24000692), Oulu University Hospital (Grant no. 2/97, 8/97, 24301140), Ministry of Health and Social Affairs (Grant no. 23/251/97, 160/97, 190/97), National Institute for Health and Welfare, Helsinki (Grant no. 54121), Regional Institute of Occupational Health, Oulu, Finland (Grant no. 50621, 54231), and ERDF European Regional Development Fund (Grant no. 539/2010 A31592). T.T.P. declares consulting fees from Gedeon Richter, Organon, Astellas, Roche; speaker's fees from Gedeon Richter, Exeltis, Roche, Stragen, Merck, Organon; and travel support from Gedeon Richter. The remaining authors declare no conflicts of interest.

Trial registration number: N/A.