Fræðigrein

Introduction: The relation between objectively measured physical activity (PA) and metabolic and cardiovascular risk factors has not been studied in Iceland. This study aimed to investigate PA and metabolic and cardiovascular risk factors among three professions: manual laborers, office workers, and farmers.

Material and methods: The participants (73 males, 89 females) underwent anthropometric measurements. Total PA and time spent in moderate-to-vigorous PA (MVPA) was assessed with activity monitors. Blood pressure was measured and fasting blood samples analyzed for total cholesterol, low- and high-density lipoprotein cholesterol, triglycerides, glucose, insulin and homeostatic model assessment.

Results: Male manual laborers and farmers were more physically active than office workers (p<0.01), but no difference was found among females. Nevertheless, female farmers spent less time in MVPA than other professions (p<0.05). Low proportion (18.4%) of all participants and none of the male office workers met the guidelines of the Directorate of Health for daily PA. Farmers had lower levels of triglycerides (p=0.01) and glucose (p<0.01), and greater fat-free mass (p<0.03) than other professions. They also had the highest levels of high-density lipoprotein cholesterol, followed by manual laborers, and then office workers (p<0.02). Total PA was significantly related to a greater number of metabolic risk factors than time spent in MVPA.

Conclusion: Farmers have the most favorable metabolic and cardiovascular risk factors in the blood and their PA and fat-free mass are a likely explanation. Regardless, their PA is low, and only one-fifth of all participants meet the guidelines for daily PA. Total PA appears more important for the metabolic and cardiovascular risk factors than time spent in MVPA.

Figure 1. Skinfold measurements conducted with a skinfold caliper (A) and physical activity monitor (B).

Figure 2.   Total physical activity (A) and time in moderate-to-vigorous physical activity (B). The values in the bars indicate the number of participants. PA = total physical activity, Time >3MET = time in moderate-to-vigorous physical activity, Man. laborers = manual laborers, Off. workers = office workers, e = male office workers different from male manual laborers and male farmers p < 0.05, f = male manual laborers different from male office workers p < 0.05, g = female farmers different from female manual laborers and female office workers p < 0.05.

Figure 3. The proportion of participants above the recommended levels for blood pressure. The values in the bars indicate the number of participants above the recommended levels. The p-values are derived from Chi-Square analysis and indicate proportional differences between the professions above recommended levels. Systolic blood pressure > 140 mmHg, diastolic blood pressure > 90 mmHg. SBP = systolic blood pressure, DBP = diastolic blood pressure.

Figure 4. The proportion of participants outside the recommended levels for blood lipids. The values in the bars indicate the number of participants outside the recommended levels. The p-values are derived from Chi-Square analysis and indicate proportional differences between the professions outside recommended levels. Cholesterol = total cholesterol, LDL = low-density lipoprotein cholesterol, HDL = high-density lipoprotein cholesterol. Total cholesterol > 6.00 mmol/L, low-density lipoprotein cholesterol L > 3.35 mmol/L, high-density lipoprotein cholesterol < 1.30 mmol/L (females) og < 1.05 mmol/L (males), triglycerides > 1.70 mmol/L.

Table I. Physical characteristics of the participants.

	Manual laborers		Office workers		Farmers
Variables	Males (n=23)	Females (n=29)	Males (n=28)	Females (n=41)	Males (n=22)	Females (n=19)
Age (yr)	51.2±8.1	51.0±8.0	53.2±6.7	49.2±6.7	52.4±8.0	48.9±7.4†
Height (cm)	177.2±5.4a	161.9±6.5	179.9±6.7	166.1±5.5	177.4±5.4	167.4±4.8*†
Weight (kg)	85.5±13.4	71.0±10.6	87.9±13.2	75.0±13.0	85.9±12.9	82.3±15.3†
BMI (kg/m2)	27.2±3.9	27.2±4.5	27.1±3.4	27.2±4.4	27.3±3.8	29.4±5.0
Waist c. (cm)	98.1±9.4	89.3±10.5	99.3±11.3	90.0±10.4	98.6±11.0	99.0±14.4†
Body fat (%)	26.9±7.5d	31.9±5.8c	25.3±5.9	35.3±5.5	21.8±5.5	36.0±6.9†‡
FFM (kg)	61.8±7.3	48.0±5.6	65.0±6.2	47.9±5.1	66.7±7.3b	52.0±6.5*†

BMI = body mass index, Waist c. = waist circumference, FFM = fat-free mass, * = main effect for working class p < 0.05, † = main effect for sex p < 0.05, ‡ = interaction between sex and working class p < 0.05, ^a = manual laborers different from office workers and farmers p < 0.05, ^b = farmers different from manual laborers and office workers p < 0.05, ^c = female manual laborers different from female office workers and female farmers p < 0.05, ^d = male manual laborers different from male farmers p < 0.05.

Table II. Blood pressure and metabolic and cardiovascular risk factors in the blood.

	Manual laborers		Office workers		Farmers
Variables	Males (n=20)	Females (n=28)	Males (n=24)	Females (n=41)	Males (n=19)	Females (n=19)
SBP (mmHg)k	137.2±17.4	140.2±12.7i	139.1±17.2j	127.2±13.9	129.0±12.7	134.7±20.9‡
DBP (mmHg)k	87.5±11.7	86.6±11.3i	89.6±10.1j	81.3±8.1	82.5±9.6	82.9±9.2‡
MAP (mmHg)k	104.1±13.1	104.5±12.4i	106.2±12.0j	96.6±9.2	98.0±10.0	100.2±12.6‡
T. chol. (mmol/L)	5.86±0.84	6.22±1.21	6.28±0.83	5.83±1.14	6.17±1.16	5.68±1.04
LDL (mmol/L)	3.72±0.96	3.85±1.04	4.26±0.66	3.70±1.16	3.91±1.20	3.14±1.13†
HDL (mmol/L)	1.60±0.29a	1.78±0.50	1.37±0.25h	1.63±0.41	1.84±0.52	2.07±0.62*†
TG (mmol/L)	1.19±0.39	1.31±0.90	1.43±0.91	1.09±0.48	0.91±0.37b	1.04±0.41*
Glucose (mmol/L)l	5.17±0.69	5.07±0.39	5.15±0.36	5.01±0.52	4.52±0.40b	4.56±0.55*
Insulin (mU/L)l	7.38±4.92	6.95±3.75	8.38±6.74	6.51±3.30	5.65±2.86	8.38±5.63
HOMAl	1.80±1.58	1.59±0.91	1.94±1.61	1.47±0.79	1.15±0.63	1.75±1.26

All comparisons adjusted for family history of coronary heart disease. SBP = systolic blood pressure, DBP = diastolic blood pressure, MAP = mean arterial pressure, T. chol. = total cholesterol, LDL = low-density lipoprotein cholesterol, HDL = high-density lipoprotein cholesterol, TG = triglycerides, HOMA = homeostatic model assessment, * = main effect for working class p < 0.05, † = main effect for sex p < 0.05, ‡ = interaction between sex and working class p < 0.05, ^a = manual laborers different from office workers and farmers p < 0.05, ^b = farmers different from manual laborers and office workers p < 0.05, ^h = office workers different from farmers p < 0.05, ⁱ = female manual laborers different from female office workers p < 0.05, ^j = male office workers different from male farmers, ^k = n=27 for female manual laborers, n=21 for male manual laborers, n=28 for male office workers, n=22 for male farmers, ^l = n=40 for female office workers.

Table III. The association of total physical activity and time in moderate-to-vigorous physical activity with metabolic and cardiovascular risk factors.

Variables	PA (Kcount/min)		Time >3MET (min/day)
	r	p	r	p
Body mass index (kg/m2)	-0.21	0.019	-0.19	0.032
Waist circumference (cm)	-0.29	0.001	-0.33	<0.001
Body fat (%)	-0.26	0.004	-0.22	0.014
Mean arterial pressure (mmHg)	-0.20	0.025	-0.05	0.582
Total cholesterol (mmol/L)	-0.08	0.407	0.02	0.789
LDL (mmol/L)	-0.14	0.118	0.03	0.747
HDL (mmol/L)	0.22	0.015	0.03	0.719
Triglycerides (mmol/L)	-0.21	0.020	-0.05	0.548
Glucose (mmol/L)	-0.31	0.001	-0.08	0.373
Insulin (mU/L)	-0.15	0.097	-0.10	0.267
HOMA	-0.20	0.027	-0.10	0.253

All associations are adjusted for sex and family history of coronary heart disease. PA = total physical activity, Time >3MET = time in moderate-to-vigorous physical activity, LDL = low-density lipoprotein cholesterol, HDL = high-density lipoprotein cholesterol, HOMA = homeostatic model assessment.