Heart at Work Study

Study Overview
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Brief Summary
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This is an observational study to examine the cardiovascular mechanisms of increased cardiovascular mortality in those with high activity occupations.

Detailed Description
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The current proposal uses a repeated-measures, within-subject design to address our aims. Twenty male participants will report to the laboratory to provide informed consent, complete baseline assessments, and receive ambulatory monitors. Following this session, each participant will wear physical activity and ambulatory cardiovascular monitors for 7 days, including at least one non-work day and one work day. Characterization of work activity will use physical activity data from self-reported time at work (Specific Aim I). The 24-hour cardiovascular load (HR and BP) and nocturnal HRV will be compared across work and non-work days (Specific Aim II). Lastly, whether fitness level or job strain modify the difference in cardiovascular strain between work vs. non-work days will be evaluated (Specific Aim III).

Official Title
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Cardiovascular Mechanisms of the Occupational Physical Activity Health Paradox: 24-hour Physical Activity, Blood Pressure, and Heart Rate

Conditions
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Occupational Diseases, Cardiovascular Diseases, Cardiovascular Risk Factor, Occupational Exposure

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: middle age (35-59 years) male self-report working full-time in the food service industry (≥30 hours/week) self-report predominantly completing light intensity activity job responsibilities (≥75% work time walking, light movement, or standing) Exclusion Criteria: Resting blood pressure of ≥150 mmHg systolic and/or ≥95 mmHg diastolic currently taking medications that are known to affect blood pressure or heart rate (e.g. Beta-blockers, ACE inhibitors, etc.) greater than low risk to participate in physical activity as determined by PAR-Q (answer of yes to any of the 7 physical activity readiness questionnaire questions) report working a second job in addition to their primary full-time job report working overnight shifts (10pm-6am) reported physical dysfunction (inability to walk 2 city blocks or climb 2 flights of stairs) inability to complete the sub-maximal exercise test to completion (80% age-predicted heart rate maximum) Currently being treated for a serious medical condition such as kidney disease, liver disease, cancer, or heart disease.

Ages Eligible for Study
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Minimum Age: 35 Years
Maximum Age: 59 Years

Sexes Eligible for Study
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Male

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 24-hour Heart Rate | We will calculate the average heart rate over each 24 hour period throughout a one week monitoring period. | 24 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 24-hour Ambulatory Systolic Blood Pressure | We will calculate the average systolic blood pressure over a 24-hour period on two separate days (workdays versus non-workdays). | 24 hours | 
| Nocturnal Heart Rate Variability, RMSSD | We will calculate the average heart rate variability during each night's sleep for a total of one week. The specific HRV variable presented is root mean square successive differences (RMSSD). | approximately 8 hours (sleep time) | 
| Physical Activity Pattern. Steps Per Day | This physical activity metric of steps per day was calculated as average number of steps during each day type (work versus non-workdays) throughout one week | 1 week | 
| Nocturnal Heart Rate Variability, SDNN | We will calculate the average heart rate variability during each night's sleep for a total of one week. The specific HRV variable presented is standard deviation of the normal to normal RR intervals (SDNN). | approximately 8 hours (sleep time) | 
| Nocturnal Heart Rate Variability, LF | We will calculate the average heart rate variability during each night's sleep for a total of one week. The specific HRV variable presented is low frequency power (LF). | approximately 8 hours (sleep time) | 
| Nocturnal Heart Rate Variability, HF | We will calculate the average heart rate variability during each night's sleep for a total of one week. The specific HRV variable presented is high frequency power (HF). | approximately 8 hours (sleep time) | 
| Physical Activity Pattern. MVPA | This physical activity metric of minutes of moderate to vigorous physical activity was calculated as average minutes during each day type (work versus non-workdays) throughout one week | 1 week | 
| Physical Activity Pattern. LPA | This physical activity metric of minutes of light physical activity was calculated as average minutes during each day type (work versus non-workdays) throughout one week | 1 week | 
| Physical Activity Pattern. Sedentary | This physical activity metric of minutes of sedentary time was calculated as average minutes during each day type (work versus non-workdays) throughout one week | 1 week | 
| Physical Activity Pattern. Upright | This physical activity metric of minutes of upright time was calculated as average minutes during each day type (work versus non-workdays) throughout one week | 1 week | 
| 24-hour Ambulatory Diastolic Blood Pressure | We will calculate the average diastolic blood pressure over a 24-hour period on two separate days (workdays versus non-workdays). | 24 hours |