Freezing cold injuries among soldiers in the Norwegian Armed Forces – A cross sectional study

Figures & data

Table 1. Clinical criteria based on levels of frostbite (19).

		Symptoms and findings	Morphology/level
Superficial frostbite	Grade 1	Reddish skin, swelling, numbness, stinging discomfort (“frostnip”), white patches (“chilblains”)	Partial intradermal frostbite
	Grade 2	Pronounced hyperaemia, blisters filled with clear fluid, superficial erosions, severe pain (gradually reduced sense of pain)	Complete dermal frostbite
Deep frostbite	Grade 3	Blisters filled with bloody fluid, bluish-white discoloration of the skin, necrosis, significantly reduced sensation of pain	Injury down to the subcutaneous tissue
	Grade 4	Deep red/bluish-black discolouration of the skin, skin is firm and immobile, full-thickness oedema, tissue necrosis, no sensation of pain	Injury to muscles and bone

Figure 1. Number of recipients and responders of the questionnaire.

Table 2. Selected questions in the FCI questionnaire for this study.

Question	Possible responses
Did you ever have frostbite during your service in the military in the period 2004–2021?	Yes, No, I don’t know
When did you have frostbite?	I don’t remember, Year listed 2004–2021
Can you specify more closely when you had the frostbite injury?	I don’t remember, Months listed
In what part of the country did the frostbite occur?	I don’t remember. Describe in free text
Did you have blisters in one of the frostbitten areas?	Yes, I had blisters, No, I didn’t have blisters, I don’t know whether I had blisters.
What colour did the blisters have?	Light, Dark, Both, I don’t remember
Can you remember whether you – at the time of injury – had symptoms other than blisters?	Pain, tingling, numbness, loss of sensitivity, bluish skin colour, whitish skin colour, reddish skin colour, muscle weakness, impaired fine motor skills, I don’t remember
Did you suffer any other physical injuries simultaneously with the frostbite (e.g. fall/cut)?	Yes, No, I don’t know
Can you describe the location of the frostbite injury/injuries on your body?	Fingers/hands, toes/feet, face/ears/cheeks, other location (describe)
What type of activity were you engaged in when you were frostbitten?	Winter exercise, field exercise, skill acquisition, shooting range duty, physical training, guard and other operative duty, basic soldiers training, other, I don’t remember.
What type of military service were you in when you were frostbitten?	National service(conscript), military training, NCO/Officer, Other (describe), I don’t remember
For how long had you served when you were frostbitten?	<3 months, 3–6 months, >6 months, I don’t remember.
In what setting was your injury discovered?	In the field during an exercise, in the field during training, in camp, I don’t remember
Who discovered your frostbite injury?	You yourself, your battle buddy, your NCO, a civilian healthcare worker, a military healthcare worker, I don’t remember
Was the frostbite first diagnosed as a different condition (e.g. friction blister)?	Yes (describe), No, I don’t remember
Have you had any long-term effects of the frostbite?	No symptoms/problems related to the frostbite, Minor health problems not affecting my daily life, Health problems that affect me at work/spear time, I have a disability that prevent me from working full time, I was forced to retrain/change my job as a result of the frostbite injury.
Do you currently have pain in the area/areas affected by frostbite?	Yes considerable pain, yes minor/moderate pain, No, I don’t know.
Do you currently have increased sensitivity to touch in the area/areas affected by frostbite?	Yes, No, I don’t know
Do you currently have increased sensitivity to cold in the area/areas affected by frostbite?	Yes, No, I don’t know
Do you currently have any tingling/prickling sensations (paraesthesia) in the area/areas affected by frostbite?	Yes, No, I don’t know
How would you assess your general state of health today?	Very good, good, moderate, poor
Did you ever have frostbite BEFORE you started serving in the military?	Yes (describe), No, I don’t know
Do you smoke?	I have never smoked, I used to smoke but I don’t any longer, I smoke occasionally, I smoke daily
Did you smoke back when you had the frostbite injury in the military?	Yes, No, I don’t know
Do you use snuff?	I have never used snuff, I used snuff in the past, but not now, I use snuff occasionally, I use snuff daily
Were you using snus back when you had the frostbite injury in the military?	Yes, No, I don’t know

Table 3. Basic characteristics of the participants.

	Total		Women		Men
	%	n = 1141	%	n = 310	%	n = 831	p-value
Sex
Men	72.8	831
Women	27.2	310
Frostbites incidents							0.211
Once	86.0	981	83.9	260	86.8	721
More than once	14.0	160	16.1	50	13.2	110
Age at frostbite, years							0.257
≤20	85.4	790	87.3	220	84.7	570
21–25	12.1	112	9.5	24	13.1	88
26 or older	2.5	23	3.2	8	2.2	15
Mean age (SD)	20.56 (2.394)		20.63 (2.752)		20.53 (2.248)		0.756**
Service time at the time of injury							0.654
Less than 3 months	34.4	267	32.1	68	35.3	199
More than 6 months	32.1	249	31.1	66	32.4	183
3–6 months	31.1	241	34.4	73	29.8	168
Do not remember	2.4	19	2.4	5	2.4	14
Type of service at injury							0.536
National service	80.5	777	82.2	212	79.9	565
Officer candidate school	11.8	114	12.0	31	11.7	83
Commander/officer	4.5	43	3.9	10	4.7	33
Other service	3.2	33	1.9	5	3.7	28
Place, end of service							<0.001
Setermoen	16.3	186	17.4	54	15.9	132
Bardufoss	13.9	159	19.7	61	11.8	98
Høybuktmoen	13.0	149	5.5	17	15.9	132
Skjold	12.1	327	7.1	22	16.2	135
Oslo	10.5	120	8.4	26	11.3	94
Rena	3.7	42	2.6	8	4.1	34
Annet	30.5	348.01	39.3	122	24.8	206
Time since injury							<0.001
0–3 years	29.8	276	48.0	121	23.0	155
4–7 years	26.1	241	30.6	77	24.4	164
8–11 years	23.2	215	14.3	36	26.6	179
>11 years	20.9	193	7.1	18	26.0	175
Mean number of years (SD)	7.02 (4.814)		4.77 (4.057)		7.86 (4.807)		<0.001**
Age at frostbite
Mean age at frostbite (SD)	20.62 (2.527)			20.53 (2.319)		20.78 (3.073)	0.438**
Grade of frostbite							0.130
Grade 1	44.3	506	68.4	147	61.4	359
Grade 2	19.3	220	22.3	48	29.4	172
Grade 3	6.5	74	9.3	20	9.2	54
Unable to establish grade	29.9	341

Note: ** Independent sample T-test, otherwise Pearson chi-square test.

Table 4. Gender and year-specific incidence of FCI among Norwegian conscripts.

		Total		FCI		No FCI
Years		%	n	%	n	%	n	p-value
2004–2021	Total		157334	0.6	925	99.4	156409
	Women	15.7	24779	1.0	252	99.0	24527	<0.001
	Men	84.3	132555	0.5	673	99.5	131882
2004–2010	Total		63821	0.4	254	99.6	63537
	Women	5.9	3767	0.8	29	99.2	3738	<0.001
	Men	94.1	60054	0.4	225	99.6	59799
2011–2015	Total		41113	0.7	276	99.3	40837
	Women	13.4	5508	1.1	58	98.9	5450	<0.001
	Men	86.6	35605	0.6	218	99.4	35387
2016–2021	Total		52400	0.8	395	99.2	52005
	Women	29.6	15504	1.1	165	98.9	15339	<0.001
	Men	70.4	36896	0.6	230	99.4	36666

Table 5. Factors associated with the frostbite severity.

	Total		Grade 1		Grade 2		Grade 3
	%	n = 1141**	%	n = 506	%	n = 220	%	n = 74	p-value
Risk factors (multiple choice)*
Use of snuff (tobacco) at the time of injury	53.3	269	57.7	131	52.1	61	48.0	24	0.360
Smoking at the time of injury	22.4	46	21.5	20	26.0	13	33.3	5	0.506^
Raynaud's phenomenon	7.8	75	9.5	44	6.7	14	13.0	9	0.233
Previous frostbite injury	3.1	30	3.4	17	1.8	4	4.1	3	0.378^
Risk, place of service									0.163
High risk garrison	68.7	529	66.9	326	75.1	160	61.4	43
Medium risk garrison	17.4	134	18.5	90	13.6	29	21.4	15
Low risk garrison	13.9	107	14.6	71	11.3	24	17.1	12
Knowledge about FCI (multiple choice)*
Knowledge of detection FCI	63.3	608	64.7	322	65.5	144	63.0	46	0.559
Knowledge of how to avoid FCI	62.2	597	62.9	322	62.1	110	64.7	66	0.559
Protective Clothing									0.811^
Armed Forces clothing according to education	87.2	837	87.6	436	86.8	191	84.9	62
Armed Forces clothing not according to education	6.4	61	5.6	28	7.3	16	6.8	5
Civilian clothing (personal clothing)	1.6	15	1.6	8	1.4	3	2.7	2
A mix of personal clothing and military clothing	3.5	34	2.7	6	5.5	4	0.0	0
Can not remember	1.4	13	1.2	6	1.8	4	0.0	0
Other risk factors (multiple choice)*
Too little sleep	16.8	161	16.7	83	17.7	39	17.8	13	0.927
Too little rest	16.3	156	17.7	88	15.5	34	15.1	11	0.701
Wet clothing	15.9	153	15.7	78	13.6	30	11.0	8	0.501
Too little nutrition	13.1	126	12.2	61	13.6	30	15.1	11	0.741
Too hard physical activity	9.9	95	10.4	52	9.5	21	8.2	6	0.812
No particular reason	31.5	302	33.1	165	30.5	67	23.3	17	0.222
Self-perceived reasons for frostbite injury (multiple choice)*
Extreme weather conditions	62.5	692	60.8	303	60.9	134	56.0	41	0.736
Commander misjudgement	38.6	427	33.3	166	35.5	78	54.8	40	0.002
My own misjudgement	23.7	262	22.7	133	30.9	68	27.4	20	0.061
Incorrect use of equipment	22.3	247	25.1	125	24.1	53	19.2	14	0.543
Commanders lack of knowledge/training	22.0	244	19.1	95	18.2	40	32.9	24	0.016
Equipment failure	21.1	234	20.3	101	18.2	40	17.8	13	0.752
My own lack of knowledge/training	15.4	170	14.3	71	13.6	30	17.8	13	0.670
Tobacco use	2.6	29	2.4	12	3.2	7	2.7	2	0.914^
Own illness	0.5	6	0.6	3	0.5	1	0.0	0	1.000^
Other reasons	27.2	301	25.9	129	29.1	64	30.1	27	0.566

Note: *Due to multiple choices, the percentage of responses might exceed 100%; ** Due to n = 341 cases without grade classification (Table 1), this number exceeds the total number presented in the grade distribution; ^Fisher exact test, otherwise Pearson chi-square test.

Table 6. Clinical associations with frostbite severity.

	Total*		Grade 1		Grade 2		Grade 3
	%	n = 1141*	%	n = 506	%	n = 220	%	n = 74	p-value
Blisters
No blisters	63.3	506	100	506	0.0	0	0.0	0	<0.001
Bright blisters	27.5	220	0.0	0	100	220	0.0	0	<0.001
Dark blisters	3.5	28	0.0	0	0.0	0	100	28	<0.001
Both light and dark blisters	5.75	46	0.0	0	0.0	0	100	46	<0.001
Frostbite site (multiple choice)
Hands	49.7	481	45.5	229	61.4	135	37.8	28	<0.001
Feet	41.2	399	42.9	216	30.0	66	52.7	39	<0.001
Face	17.7	171	21.1	106	14.5	32	16.2	12	0.099
Other sites	3.2	31	4.4	22	1.8	4	0.0	0	0.056^
Frostbite treatment									<0.001
Yes	10.4	119	6.7	32	15.4	33	29.9	20
No	81.6	931	93.3	447	84.6	181	70.1	47
Frostbite treatment level (multiple choice)
In the army	6.6	75	56.3	18	75.8	25	60.0	12	0.228
Local/central hospital	3.2	36	18.8	6	27.3	9	55.0	11	0.019
GP office	2.0	23	21.9	7	18.2	6	20.0	4	0.942^
Emergency room	0.7	8	0.0	0	9.1	3	20.0	4	0.025^
Complementary and alternative medicine provider	0.7	8	6.3	2	6.1	2	0.0	0	0.667^
Other	1.7	19	18.8	6	21.2	7	20.0	4	1.000^
Type of treatment (multiple choice)
Painkiller tablets	5.4	62	50.0	16	63.6	21	70.0	14	0.309
Blood thinner tablets	1.5	17	12.5	4	12.1	4	30.0	6	0.203^
Injections	1.4	16	6.3	2	6.1	2	15.0	3	0.526^
Complementary and alternative medicine	1.0	11	12.5	4	9.1	3	0.0	0	0.259^
Surgical	0.4	5	0.0	0	0.0	0	20.0	4	0.003^
Other	5.4	62	59.4	19	66.7	22	25.0	5	0.010
Type of sequela after injury (multiple choice)
Cold hypersensitivity	66.4	758	94.8	313	95.4	146	94.7	54	0.932^
Pain	34.5	277	33.6	111	32.0	49	38.6	22	0.236^
Parasthesia	24.1	275	27.0	89	35.3	54	43.9	25	0.006^
Hypersensitivity to touch	13.6	155	16.7	55	22.2	34	31.6	18	0.086
General health situation (at time of the survey)									0.219^
Very good	63.1	702	65.8	329	66.8	147	60.3	44
Good	33.9	377	32.4	162	30.0	66	37.0	27
Not quite good	2.5	29	1.8	9	3.2	7	1.4	1
Bad	0.4	4	0.0	0	0.0	0	1.4	1

Note: *Due to cases not classified with grade, this number might differ from the total number presented in the grade distribution; ^ Fisher exact test, otherwise Pearson chi-square test.