Table 3.

Factors associated with cognitive function (Raven’s Progressive Matrices scores) in multivariable analysis.

Variables	β	(95% CI)	p-valuea
Gender
Male		[Reference]	0.002
Female	3.92	[1.46,6.38]
Season of birth
Summer (May, June, July)		[Reference]	0.009
Fall (August, September, October)	−3.81	[−7.16, −0.46]
Winter (November, December, January)	−4.87	[−8.19, −1.56]
Spring (February, March, April)	−5.24	[−8.64, −1.84]
Province
Capital		[Reference]	<0.001
Hawally	0.76	[−3.73,5.26]
Farawanya	−9.97	[−14.61, −5.32]
Jahra	−6.07	[−11.08, −1.06]
Mubarak al-Kabeer	1.69	[−3.38,6.77]
Ahmadi	−0.83	[−5.18,3.52]
Father’s education
Intermediate school or below		[Reference]	<0.001
Secondary (high-school)	−0.18	[−4.01,3.65]
Diploma	1.93	[−2.27,6.13]
University and above	6.27	[2.42,10.12]
Mother’s education
Intermediate school or below		[Reference]	0.025
Secondary (high-school)	1.89	[−2.45,6.22]
Diploma	1.37	[−3.13,5.87]
University and above	5.19	[0.96,9.43]
Type of housing			<0.001
Rented flat		[Reference]
Rented house	−7.93	[−12.22, −3.63]
Owned flat	−1.94	[−8.24,4.36]
Owned house	−4.64	[−7.42, −1.85]
Cigarettes smoking at home
No		[Reference]
Yes	−2.79	[−5.34, −0.25]	0.031
Sleep hours during the weekends
First tertile (<9 hours)		[Reference]	0.017
Second tertile (9 to<11 hours)	0.10	[−2.94,3.33]
Third tertile (≥ 11 hours)	−3.49	[−6.76, −0.22]
Grade level
Six		[Reference]	<0.001
Seventh	3.17	[0.32,6.03]
Eights	5.60	[2.68,8.54]
Consumptions of soft drinks per week
Zero time		[Reference]	<0.001
One per week times	−6.46	[−10.81, −2.10]
Two per week times	−3.60	[−7.77,0.56]
Three per week times	−6.24	[−10.81, −1.67]
Four to six times	−5.93	[10.87, −1.00]
Seven times or more	−9.92	[−14.30, −5.54]
Parathyroid Hormone (pmol/L)	−0.23	[−0.47,0.01]	0.065

^ap-values were generated by partial F-test.