Trends in silicosis prevalence and the healthy worker effect among gold miners in South Africa: a prevalence study with follow up of employment status

Table 2 Comparison of prevalence of silicosis by age: 1984 study [7, 8] versus current study (ILO grade ≥1/0)

1984 study				Current study
Age (years)	N (%)	Cases n	Silicosis prevalence % (95 % CI)^a	Age (years)	N	Age distribution %	Silicosis prevalence (reader I) % (95 % CI)^b	Silicosis prevalence (combined reading) (%)
≤45	125,038 (94.2)	1009	0.8 (0.8, 0.9)	≤44	6468	56.4	2.0 (1.5, 2.7)	0.9
46+	7726 (5.8)	801	10.4 (9.7, 11.1)	45+	4994	43.6	10.5 (8.6, 12.9)	13.2
Crude	132,765	1810	1.4 (1.3, 1.4)	Crude	11,462	100	5.7 (4.6, 7.1)	6.2
Adjusted^c			5.0

All figures rounded to one decimal
^a95 % confidence intervals using binomial exact standard errors
^b95 % confidence intervals adjusted for clustering using robust standard errors
^cAge standardised to current study age distribution

ISSN: 1471-2458