Table 1.
Basic characteristics and mitochondrial DNA biomarkers in welders (n = 101) and controls (n = 127)
| Welder | Control | p g | |
|---|---|---|---|
| Agea | 41 (23 – 60) | 43 (23 – 56) | 0.94 |
| BMI (kg/m2)a | 28 (22 – 34) | 27 (22 – 34) | 0.70 |
| Respirable dust (mg/m3)a,b | 1.1 (0.2 – 8.4) | 0.1 (0.0 – 0.1) | <0.001h |
| Working years as welder (year)a | 15 (1 – 38) | --- | -- |
| Systolic blood pressure (mm Hg)a | 130 (115 – 155) | 125 (105 – 145) | <0.001 |
| Diastolic blood pressure (mm Hg)a | 75 (60 – 85) | 70 (60 – 85) | <0.001 |
| Previous smoking (yes/no (%)) | 43/58 (43%) | 43/83 (34%) | 0.21i |
| Previous smoking years (year)a | 10 (3 – 32) | 14 (2 – 31) | 0.52 |
| Smokeless tobacco “snus” (yes/no (%)) | 28/73 (28%) | 24/103 (19%) | 0.15i |
| Relative mtDNA copy numbera | 1.13 (0.84 – 1.52) | 1.00 (0.74 – 1.50) | 0.0049 |
| D-loop methylationa, c | 13.4 (10.5 –20.8) | 15.6 (10.9 – 21.1) | 0.0012 |
| MT-TF methylationa, c | 3.4 (0 – 9.5) | 4.5 (0 – 12.1) | 0.0015 |
| mtDNA function group (high/low (%)) (D-loop)d, f | 57/37 (60%) | 51/66 (44%) | 0.026i |
| mtDNA function group (high/low (%)) (MT-TF)e, f | 63/37 (63%) | 47/73 (39%) | <0.001i |
aPresented as median (5 – 95 percentile)
bMedian of respirable dust in welder group was based on 70 welders with measured respirable dust
cMedian of D-loop methylation was based on 211 participants (94 welders and 117 controls); median of MT-TF methylation was based on 220 participants (100 welders and 120 controls)
dDerived from unmethylated D-loop and relative mtDNA copy number: Relative number of unmethylated D-loop = (100% - % methylated D-loop) × relative mtDNA copy number
eDerived from unmethylated MT-TF and relative mtDNA copy number: Relative number of unmethylated MT-TF = (100% - % methylated MT-TF) × relative mtDNA copy number
fStratified into low and high groups based on the median. Here, we present the count (%) of participants in each function group
g p value obtained from t test unless marked otherwise
h p values obtained from Mann–Whitney U test
i p values obtained from Fisher’s exact test