Table 2.
Characteristics of studies and evaluation of Newcastle-Ottawa Scale
| NOS | ||||||||
|---|---|---|---|---|---|---|---|---|
| Study design | First author, year | Participants | Age range (years) | Definition of tooth loss | Focal point | Dose-response | Coding | Score |
| Cross-sectional study | Randolph, 2001 | 3,050 Mexican American | 65-99 | 15+ | F | NA | 011 11 1 | 5* |
| Klein, 2004 | 2,764 American | 53-96 | 1+ | F | NA | 011 11 1 | 5* | |
| Tanaka, 2005 | 1,002 Japanese pregnant women | 29.8 on average | 1+ | S | NA | 010 11 0 | 3 | |
| Hanioka, 2007 | 2,200 Japanese | 60-94 | Total tooth loss | S | NA | 101 10 1 | 4 | |
| Musacchio, 2007 | 1,226 Italian males | 65+ | Total tooth loss | S | NA | 101 11 1 | 5* | |
| Ojima, 2007 | 1,314 Japanese | 20-39 | 1+ | S | 3/4 levels | 111 01 1 | 5* | |
| Hanioka, 2007 | 3,999 Japanese | 40-94 | 9+ | S | 3/4 levels | 111 11 1 | 6* | |
| Mundt, 2007 | 2,501 German | 25-59 | 15th percentile | F | 3 levels | 111 11 1 | 6* | |
| Yanagisawa, 2009 | 547 Japanese males | 55-75 | 9+ | S | 3 levels | 110 11 0 | 4 | |
| Yanagisawa, 2010 | 1,088 Japanese males | 40-75 | 9+ | S | 3 levels | 110 11 0 | 4 | |
| NOS | ||||||||
| Study design | First author, year | Participants | Age range (years) | Duration of observation | Focal point | Dose-response | Coding | Score |
| Cohort study | Slade, 1997 | 693 Australian | 60+ | 2 years | F | NA | 10 01 110 | 4 |
| Krall, 2006 | 789 American males | 21-84 | 36 years | S | NA | 00 11 111 | 5* | |
| Okamoto, 2006 | 740 Japanese males | 30-59 | 4 years | S | 3 levels | 00 10 110 | 3 | |
| Dietrich, 2007 | 43,112 American male health professionals | 40-75 | 16 years | S | 5 levels | 01 11 111 | 6* | |
| Cunha-Cruz, 2008 | 12,264 American HMO members | 45-61 | 3 years | A | NA | 00 10 110 | 3 | |
Studies were conducted in Japan, the United States, Australia, Germany and Italy. A dose-response relationship was examined in 7 studies, and 8 studies (6 for cross-sectional and 2 for prospective cohort studies) were classified as high quality.
S, smoking; F, factors including smoking; A, systemic antibodies; *evaluated for high-quality methodology by the modified Newcastle-Ottawa Scale (NOS). One star each was given for six and seven items for cross-sectional and cohort studies, respectively, if the methodology of a study satisfied the criterion. The items were divided according to three categories of selection, comparability and exposure for cross-sectional studies and selection, comparability and outcome for cohort studies. When a study satisfied all criteria, the star column appears as 111 11 1 for cross-sectional and 11 11 111 for cohort studies. Studies with total scores of five or more, three or four, and two or less were evaluated as high-, moderate- and low-quality studies, respectively.