Table 3.

Age and sex standardised prevalences (numbers of participants) of respiratory illness by smoking status, and prevalence ratios in 1996 compared with 1972-6 in men and women aged 45-54 years

	1972-6	1996	Prevalence ratio adjusted for age and sex	Prevalence ratio adjusted for all covariates*
Never smokers	n=540	n=495
Hay fever	5.8 (34)	19.9 (110)	4.17 (2.75 to 6.32)	3.53 (2.30 to 5.43)
Asthma:
In those without hay fever	1.8 (12)†	6.3 (23)†	2.54 (1.21 to 5.33)	2.86 (1.36 to 6.02)
In those with hay fever	18.1 (8)‡	13.0 (19)‡	0.65 (0.24 to 1.77)	0.76 (0.25 to 2.36)
All	3.0 (20)	8.2 (42)	2.38 (1.34 to 4.23)	2.60 (1.41 to 4.80)
Wheeze	4.6 (24)	1.1 (6)	0.31 (0.12 to 0.80)	0.32 (0.11 to 0.90)
Chronic sputum	5.1 (26)	5.1 (28)	1.03 (0.60 to 1.79)	1.11 (0.60 to 2.04)
Breathlessness	8.3 (55)	6.3 (32)	0.68 (0.42 to 1.09)	0.92 (0.55 to 1.53)
Asthma and/or wheeze	6.4 (37)	8.5 (44)	1.33 (0.83 to 2.15)	1.40 (0.83 to 2.36)
Ever smokers	n=1168	n=629
Hay fever	5.4 (64)	15.5 (97)	3.21 (2.28 to 4.53)	2.76 (1.91 to 3.98)
Asthma:
In those without hay fever	1.0 (13)†	3.4 (18)†	3.17 (1.57 to 6.42)	2.92 (1.37 to 6.23)
In those with hay fever	11.6 (7)‡	15.9 (16)‡	1.46 (0.54 to 3.95)	0.95 (0.33 to 2.76)
All	1.6 (20)	5.3 (34)	3.36 (1.94 to 5.82)	2.69 (1.49 to 4.84)
Wheeze	14.2 (173)	8.1 (49)	0.53 (0.37 to 0.76)	0.79 (0.53 to 1.17)
Chronic sputum	23.9 (285)	14.2 (88)	0.50 (0.38 to 0.66)	0.73 (0.55 to 0.97)
Breathlessness	12.0 (140)	8.8 (57)	0.75 (0.54 to 1.05)	0.85 (0.59 to 1.22)
Asthma and/or wheeze	15.1 (184)	12.0 (75)	0.77 (0.57 to 1.04)	1.04 (0.76 to 1.43)

Standardisation for age differences means that percentages differ from estimates based on raw numerators and denominators. 

^*Age, sex, and social class in never smokers; and age, sex, social class, pack years, and former or current status in ever smokers. 

^†Denominator is those without hay fever. 

^‡Denominator is those with hay fever.