Table 4.

Rates of mortality from diseases of the circulatory system in winter and non-winter months, ratio of rates and relative change in winter:non-winter ratios for potential modifying factors; 1996–2000

	Rate per 10,000 person years (No of deaths)*		Winter:non-winter ratio (95% CI)‡ Unadjusted	Winter:non-winter ratio relative to baseline category§ (95% CI)‡	p-value
	Winter	Non-winter
All	33.7 (20664)	27.4 (33576)	1.24 (1.13, 1.36)
Age (years):
0–4	0.1 (3)	0.2 (18)	0.33 (.09, 1.22)	1.00†
5–14	0.1 (6)	0.0 (8)	1.50 (0.52, 4.31)
15–29	0.4 (50)	0.4 (112)	0.89 (0.62, 1.27)
30–59	6.8 (1678)	6.2 (3065)	1.05 (0.76, 1.46)	1.30 (0.90, 1.90)
60–79	100.7 (8057)	83.1 (13264)	1.16 (0.95, 1.40)	1.40 (1.00, 1.96)
80+	640.2 (10870)	505.1 (17109)	1.25 (1.13, 1.37)	1.44 (0.99, 2.08)	p = .22
Gender:
Male	33.8 (10148)	28.0 (16773)	1.28 (1.13, 1.46)	1.00
Female	33.6 (10516)	26.9 (16803)	1.21 (1.06, 1.37)	1.06 (0.94, 1.19)	p = .33
Ethnicity^:
Non-Maori	32.3 (19071)	26.2 (30797)	1.27 (1.15, 1.40)	1.00
Maori	55.8 (1593)	46.7 (2779)	1.18 (0.96, 1.44)	0.93 (0.81, 1.07)	p = .32
NZDep96:
1–3	28.7 (4742)	23.5 (7733)	1.20 (1.01, 1.42)	1.00
4–6	34.2 (6325)	27.9 (10292)	1.23 (1.05, 1.45)	1.07 (0.92, 1.24)
7–10	36.4 (9597)	29.6 (15551)	1.28 (1.10, 1.49)	1.04 (0.90, 1.20)	p = .67
RHA:
North	29.1 (6132)	23.7 (9997)	1.24 (1.03, 1.49)	1.00
Midland	34.4 (4200)	27.7 (6754)	1.34 (1.11, 1.62)	0.97 (0.83, 1.15)
Central	35.7 (5338)	28.7 (8563)	1.17 (0.97, 1.42)	1.00 (0.85, 1.18)
South	38.2 (4994)	31.7 (8262)	1.21 (1.00, 1.48)	0.96 (0.81, 1.13)	p = .93

* No of deaths in winter correspond to a 4 month period; non-winter, an 8 month period

‡ Generalised negative binomial regression model; overdispersion a linear combination of age group and ethnicity

§ Adjusted for all other covariates including covariate by winter interaction terms

† Because of small cell counts, age group 0–29 years was used as the baseline category

^ Mortality rates have been age-standardised to account for different population structures of Maori and Non-Maori