Participants
This community outreach project was performed by the university and community partnership between Augusta University and Costa-Layman Farm during the summers 2013 to 2017. The Costa-Layman nursery is a wholesale supplier for perennials, located in Trenton, South Carolina. It was established in 1990, consisting of three farms, collectively totaling more than 1200 acres. Fliers were distributed among the employees and were posted on the noticeboards throughout the farms. All the employees working at the Costa-Layman Farms were invited to participate in this annual health-screenings. The consent form was translated in Spanish with proofreading from certified medical interpreters. Study information and consent process were conducted during the farm business hours with help of certified Spanish interpreters. Written informed consent was obtained from each participant. One hundred and thirteen subjects had their HGS and spirometry obtained. The protocol was approved by the Institutional Review Board at Augusta University. All measurements were performed in the morning at the Costa-Layman horticulture farm.
Demographics
Anthropometry, blood pressure, and smoking status
Height and weight were obtained according to standard procedures, using a wall-mounted stadiometer (Tanita Corporation of American, Arlington Heights, IL) and calibrated electronic scale (model CN2OL; Cardinal Detecto, Webb City, MO). Body mass index (BMI) was calculated using CDC formula, weight (kg)/height (m2) for which we used for body weight classification: < 25 kg/m2 (normal weight), 25 -29.9 kg/m2 (overweight), or ≥ 30 kg/m2 (obese)[12]. After 5 minutes of rest, systolic (SBP) and diastolic blood pressures (DBP) were measured twice, each at least 1 minute apart, in sitting position using manual mercury sphygmomanometer by trained research staff. The averages of two measurements were reported and used for analyses. Smoking status was assessed by self-reporting asking subjects whether they have ever smoked at least once in their lifetime. Number of packs and years of smoking were also asked.
Biochemical Variables
Venous blood was collected after an overnight fast, and all blood samples were centrifuged immediately and stored at -80°C for analysis. Samples were collected while fasting. Glycosylated hemoglobin (HbA1C) and lipid profile (total cholesterol, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and triglycerides) were assessed by standard clinical laboratory methods at Premier Medical Laboratory Services (Greenville, SC). HbA1C was determined based on turbidimetric inhibition immunoassay. Lipid parameters were measured by an enzymatic colorimetric method, using automated analyzer (Cobas c 311/501 and Cobas c 502) and Cobas enzymatic reagents.
Handgrip strength measurement
Isometric handgrip strength was measured using a Jamar Hydraulic Hand Dynamometer (Jamar; Bolingbrook, IL). Grip strength was measured in both hands in a seated position with the arm at a 90-degree angle according to the National Health and Nutrition Examination Survey guidelines for hand dynamometry.26 Handgrip strength was measured three times, and the highest score was used for each hand. The combined strength (in kilograms) of the right and left hands were used to create the absolute handgrip value. The relative handgrip was then calculated as the absolute handgrip divided by their BMI (kg/BMI).27
Pulmonary function test (PFT)
American Thoracic Society (ATS) standard protocol was followed and administered by licensed respiratory therapists. Subjects blew three times to measure forced vital capacity (FVC) for each effort. If FVC was normal during the first effort, then test ended. If FVC was abnormal, then subjects blew three more efforts. If any result did not meet ATS standard, no further testing occurred. If all three results were abnormal and met ATS standard, then subjects were advised to visit their primary care physician for further evaluation. Forced expiratory volume in 1 second (FEV1), FEV1%predicted, peak expiratory flow (PEF), PEF%predicted, FEF 25–75%, FEF 25–75%predicted, FEV1/FVC and FEV1/FVC%predicted were collected as well. SAD was defined as FEF25 − 75% ≤ 60% and OLD was defined as FEV1/FVC < 70% per Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria.14,15
Statistical Analysis
Statistical analyses were performed using SPSS software (version 25, IBM SPSS Statistics, Chicago, IL). P-values < .05 were considered statistically significant for all analyses. Normal distribution and homogeneity of variances were confirmed by Shapiro-Wilks W and Leven’s tests, respectively. Continuous variables were summarized by median and ranges. Categorical variables were summarized by relative frequencies. Categorical variables were analyzed using chi-square tests, whereas continuous variables were compared using t-tests. LDL, HDL and triglycerides were log-transformed. Partial Pearson’s correlation coefficients were used to examine the associations of FEF25 − 75% and FEV1/FVC with risk factors. Multivariate linear regressions were used to estimate beta (β) and 95% confidence intervals (CI) for pulmonary function according to age, sex, smoking status, BMI, HbA1C, lipid profile and HGS.