Sleep deprivation can lead to increased body weight and blood pressure (BP), but the latent effects of partial sleep deprivation related to required night sentry duties within a short-term period on cardiometabolic characteristic changes in military personnel are unclear.

To investigate the association between night sentry duty frequency in the past 3 months and cardiometabolic characteristics in armed forces personnel.

A total of 867 armed forces personnel who were aged 18-39 years and did not take any antihypertensive medications in Taiwan in 2020 were included. The frequency of night sentry duty was self-reported via a questionnaire (average number of night sentry shifts per month for the past 3 months). Hemodynamic status was assessed via the resting BP and pulse rate (PR). Cardiometabolic risk factors were defined according to the International Diabetes Federation criteria. Multivariable linear regression analyses of the associations between night sentry duties and PR, BP, and other metabolic syndrome (MetS) marker levels were performed, with adjustments for age, sex, substance use, body mass index and aerobic fitness. Multiple logistic regression analysis was carried out to determine the associations between night sentry duties and the prevalence of each MetS feature.

There was an association between night sentry duties and PR [standardized β (standard error) = 0.505 (0.223), P =0.02], whereas there was no association with systolic and diastolic BP. In addition, there was an inverse association between night sentry duties and high-density lipoprotein cholesterol (HDL-C) levels [standardized β = -0.490 (0.213), P = 0.02], whereas there was no association with the other metabolic marker levels. Compared with personnel without night sentry duties, those with ≥ 1 night sentry shift/month had a greater risk of impaired fasting glucose (≥ 100 mg/dL) [odds ratio: 1.415 (confidence interval: 1.016-1.969)], whereas no associations with other MetS features were found.

Among military personnel, the burden of night sentry duty was positively associated with the resting PR but inversely associated with HDL-C levels. In addition, personnel with partial sleep deprivation may have a greater risk of impaired fasting glucose than those without partial sleep deprivation.

Habitual substance use, i. e., alcohol, tobacco and betel nut, has been found with an increased risk of metabolic syndrome (MetS) in the general population, whereas the association remains unclear in physically fit military personnel. This study aimed to investigate the combination of these substances use and their associations with new-onset MetS in the military.

A total of 2,890 military men and women, aged 18-39 years, without MetS were obtained from the cardiorespiratory fitness and health in eastern armed forces study (CHIEF) in Taiwan and followed for incident MetS from baseline (2014) through the end of 2020. Incident MetS event was defined by the International Diabetes Federation guideline and confirmed in the annual health examinations. A self-report was used to assess the alcohol, tobacco and betel nut use status (active vs. former/never). Multivariable Cox regression model was performed to determine the association with adjustments for sex, age, body mass index and physical activity at baseline.

At baseline, there were 279 active betel nut chewers (9.7%), 991 active smokers (34.3%) and 1,159 active alcohol consumers (40.1%). During a mean follow-up of 6.0 years, 673 incident MetS (23.3%) were observed. As compared to no substance users, only one substance, and two and three substances users had a greater risk of incident MetS [hazard ratios (HRs) and 95% confidence intervals: 1.27 (1.06-1.54), 1.38 (1.12-1.69) and 1.78 (1.37-2.32), respectively]. In subgroup analyses, the risk of incident MetS in two and three substances users was significantly greater in those free of baseline low high-density lipoprotein [HRs: 1.54 (1.21-1.95) and 2.57 (1.92-3.46), respectively], as compared to their counterparts (both p for interactions <0.05).

A dose-response association of more substances use for new-onset MetS was noted in military personnel. This finding suggests that the combined alcohol, tobacco and betel nut use may play a role in the development of MetS. Further study is required to establish causation and to investigate the potential benefits of substance use cessation in reducing the risk of MetS.