Table 1

Demographic and medical characteristics of farmers in the Agricultural Health Study by wheeze status, 1994–97

	All participants (n=20468)
	Wheeze n=3838		No wheeze n=16630
	n	%	n	%	p value†
*Atopy defined as self report of hay fever or eczema.
†p value for χ² test.
‡Compared to never smokers.
§Compared to no atopy, no asthma.
Age category
<20 years	28	1	108	1	0.009
21–30 years	294	8	1156	7
31–40 years	917	24	3628	23
41–50 years	986	26	4296	26
51–60 years	814	21	3922	24
61–70 years	617	16	2762	17
>70 years	182	5	758	5
Race					NS
White	3722	98	16090	98
Other	78	2	361	2
Sex					NS
Female	89	2	402	2
Male	3749	98	16228	98
State					<0.01
Iowa	2423	63	11496	69
North Carolina	1415	37	5134	31
Smoking status
Never	1680	44	9497	57
Past	1255	33	5399	33	<0.01‡
Current	903	24	1734	10	<0.01‡
Atopy*: asthma status
No atopy: no asthma	2667	69	14860	89
Atopy: no asthma	498	13	1407	8	<0.01§
No atopy: asthma	309	8	127	1	<0.01§
Atopy: asthma	364	9	236	1	<0.01§