Table 1.

Characteristics of Case and Noncase Patients With Rheumatoid Arthritis, Sister Study, United States, 2004–2009

Characteristic	Case Patients With RA (n = 424)		Noncase Patients (n = 48,919)
	No.	%	No.	%
Age at enrollment, yearsa	57.9 (8.2)		55.1 (9.0)
Pack-years of smokinga,b	17.4 (16.1)		14.6 (15.3)
Birth year
1928–1945	163	38	14,051	29
1946–1955	177	42	19,211	39
1956–1965	73	17	13,014	27
After 1965	11	3	2,643	5
Never smoker	184	43	26,451	54
College degree	170	40	23,770	49
Nonwhite or Hispanic race or ethnicity	82	19	7,764	16
No. of childhood socioeconomic factorsc
0	113	28	17,300	37
1	124	31	15,858	24
2	126	31	10,389	22
3–4	42	11	3,404	8
Age at home of longest residenced
Childhood (age ≤14 years)	102	27	10,340	24
Adulthood (age ≥18 years)	207	49	21,548	44
Home of longest residence was a farme
Childhood (age ≤14 years)	65	15	6,822	16
Adulthood (age ≥18 years)	36	8	3,451	7
Other farm residence ≥12 months	41	10	3,489	7

Abbreviation: RA, rheumatoid arthritis.

^a Values are expressed as mean (standard deviation).

^b Missing data on pack-years of smoking for 19 case patients (4%) and 1,387 noncase patients (3%).

^c Score of 4 factors previously associated with RA in the sample: highest childhood household educational level is high school or less, low/poor relative household income, young maternal age (<20 years), food insecurity (21); missing data for 19 case patients (4%) and 1,968 noncase patients (4%); percentages do not add to 100 because of rounding.

^d Missing childhood residence data for 43 case patients (10%) and 5,053 noncase patients (10%). Childhood residential pesticide use and adult residential pesticide use are not mutually exclusive.

^e Missing childhood farm residence on 47 case patients (11%) and 5,065 noncase patients (10%). Responses for childhood farm residence and adult farm residence are not mutually exclusive. Those who reported neither were asked about other residential farm experience of 12 months or longer.