Risk factors for vitamin D deficiency in women aged 20–50 years consulting in general practice: a cross-sectional study

Figures & data

Table I. Characteristics of the women included in this study.

		Whole study population n (%) n = 196	Women without concealing clothes n (%) n = 135	Women with concealing clothes n (%) n = 61	P
Age (years)	19–34	83 (42.6)	51 (38.1)	32 (52.5)
	35–44	74 (37.8)	50 (37.3)	24 (39.3)	0.019
	44–49	38 (24.6)	33 (24.6)	5 (8.2)
Pregnancy	≥3	67 (34.2)	38 (28.4)	29 (47.5)	0.018
Employment	Yes	132 (68.1)	110 (82.7)	39 (63.9)	<0.001
	No	62 (31.9)	23 (17.3)	22 (36.1)
Socially disadvantaged	Yes	46 (23.6)	20 (14.9)	26 (42.6)	<0.001
	No	149 (76.4)	115 (85.1)	35 (57.4)
BMI	<25	122 (62.3)	92 (69.7)	30 (50.0)	0.009
	>25	70 (35.7)	40 (30.3)	30 (50.0)

Figure 1. Blood plots of 25(OH)D concentrations.

Table II. Prevalence of vitamin D deficiency based at different thresholds.

	Whole study population n (%)	Women without concealing clothes n (%)	Women with concealing clothes n (%)	P
Vitamin D < 30 nmol/l	105 (53.6)	53 (39.3)	52 (85.2)	<0.001
Vitamin D < 52 nmol/l	158 (80.6)	99 (73.3)	59 (96.7)
Vitamin D < 75 nmol/l	188 (95.9)	128 (94.8)	60 (98.4)	<0.001
Vitamin D ≥ 75 nmol/l	8 (4.1)	7 (5.2)	1^a (1.6)	0.245

^aThis woman received 100 000 UI one month before.

Table III. Risk factors for vitamin D deficiency in women with and without concealing clothing.

Studied factor	Risk factor	Women with concealing clothing n (%)	Women without concealing clothing n (%)	P
Photo type	IV and V	39 (63.9)	40 (30.1)	<0.001
Sunshine exposure
Proportion of skin	Not full body exposed	53 (86.9)	66 (39.6)	<0.001
Time of day	Not between 12:00 and 16:00	10 (56.7)	41 (30.6)	0.003
Duration	<1 week	33 (57.9)	38 (29.0)	<0.001
Location	City	32 (54.2)	33 (25.2)	<0.001
Time since exposure	>5 months	20 (40.8)	38 (32.5)	0.416
Sun cream use	No use	38 (65.5)	55 (41.0)	0.002
Outing frequency	<once per day	17 (28.8)	26 (19.4)	0.265
Sport practise	Not outdoor sports	57 (93.5)	104 (79.0)	0.003
Body mass index	>25	30 (50.0)	40 (30.3)	0.009
Vitamin D intake	<5 μg/day	57 (96.6)	129 (99.2)	0.065
Food supplement use	Yes	51 (88.0)	116 (90.0)	0.684
Employment	Without	39 (63.9)	23 (17.3)	<0.001
Socially disadvantaged	Yes	26 (42.6)	20 (14.9)	<0.001

Table IV. Odds ratios of risk factors for two thresholds of vitamin D deficiency (univariable logistic regression).

Risk factor	25(OH)D < 52 nmol/l	25(OH)D < 30 nmol/l
Concealing clothing	1.32 (1.18–1.47)	2.17 (1.71–2.74)
Photo type: III	NS	0.57 (0.43–0.75)
IV or V	1.23 (1.08–1.39)	1.73 (1.35–2.21)
Sunlight exposure
No full-body exposure	1.38 (1.15–1.62)	2.46 (1.67–3.60)
No exposure 12:00–16:00	1.19 (1.05–1.36)	1.61 (1.25–2.09)
< 1 week summer exposure	1.23 (1.07–1.40)	1.65 (1.26–2.14)
City exposure	1.24 (1.09–1.41)	1.71 (1.32–2.20)
Time since exposure	NS	NS
Sun cream use	0.847 (0.73–0.97)	0.616 (0.46–0.82)
Outing frequency	NS	NS
Sport: no outdoor sports	1.48 (1.09–1.99)	2.18 (1.23–3.87)
Body mass index > 25	1.14 (1.00–1.31)	1.35 (1.04–1.75)
Dietary intake < 5 μg/day	NS	NS

CI, 95% confidence interval; NS, not significant.